Now that the DMA BUF heaps core code has been queued, I wanted to send out some of the pending changes that I've been working on.
For use with Android and their GKI effort, it is desired that DMA BUF heaps are able to be loaded as modules. This is required for migrating vendors off of ION which was also recently changed to support modules.
So this patch series simply provides the necessary exported symbols and allows the system and CMA drivers to be built as modules.
Due to the fact that dmabuf's allocated from a heap may be in use for quite some time, there isn't a way to safely unload the driver once it has been loaded. Thus these drivers do no implement module_exit() functions and will show up in lsmod as "[permanent]"
Feedback and thoughts on this would be greatly appreciated!
thanks -john
Cc: Laura Abbott labbott@redhat.com Cc: Benjamin Gaignard benjamin.gaignard@linaro.org Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Pratik Patel pratikp@codeaurora.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Andrew F. Davis afd@ti.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Yue Hu huyue2@yulong.com Cc: Mike Rapoport rppt@linux.ibm.com Cc: Chenbo Feng fengc@google.com Cc: Alistair Strachan astrachan@google.com Cc: Sandeep Patil sspatil@google.com Cc: Hridya Valsaraju hridya@google.com Cc: dri-devel@lists.freedesktop.org
John Stultz (1): dma-buf: heaps: Allow system & cma heaps to be configured as a modules
Sandeep Patil (1): mm: cma: Export cma symbols for cma heap as a module
drivers/dma-buf/dma-heap.c | 2 ++ drivers/dma-buf/heaps/Kconfig | 4 ++-- drivers/dma-buf/heaps/heap-helpers.c | 2 ++ kernel/dma/contiguous.c | 1 + mm/cma.c | 5 +++++ 5 files changed, 12 insertions(+), 2 deletions(-)
From: Sandeep Patil sspatil@google.com
Export cma_get_name, cma_alloc, cma_release, cma_for_each_area and dma_contiguous_default_area so that we can use these from the dmabuf cma heap when it is built as module.
Cc: Laura Abbott labbott@redhat.com Cc: Benjamin Gaignard benjamin.gaignard@linaro.org Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Pratik Patel pratikp@codeaurora.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Andrew F. Davis afd@ti.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Yue Hu huyue2@yulong.com Cc: Mike Rapoport rppt@linux.ibm.com Cc: Chenbo Feng fengc@google.com Cc: Alistair Strachan astrachan@google.com Cc: Sandeep Patil sspatil@google.com Cc: Hridya Valsaraju hridya@google.com Cc: dri-devel@lists.freedesktop.org Signed-off-by: Sandeep Patil sspatil@google.com [jstultz: Rewrote commit message, added dma_contiguous_default_area to the set of exported symbols] Signed-off-by: John Stultz john.stultz@linaro.org --- kernel/dma/contiguous.c | 1 + mm/cma.c | 5 +++++ 2 files changed, 6 insertions(+)
diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index 69cfb4345388..ff6cba63ea6f 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -31,6 +31,7 @@ #endif
struct cma *dma_contiguous_default_area; +EXPORT_SYMBOL(dma_contiguous_default_area);
/* * Default global CMA area size can be defined in kernel's .config. diff --git a/mm/cma.c b/mm/cma.c index 7fe0b8356775..db4642e58058 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -24,6 +24,7 @@ #include <linux/memblock.h> #include <linux/err.h> #include <linux/mm.h> +#include <linux/module.h> #include <linux/mutex.h> #include <linux/sizes.h> #include <linux/slab.h> @@ -54,6 +55,7 @@ const char *cma_get_name(const struct cma *cma) { return cma->name ? cma->name : "(undefined)"; } +EXPORT_SYMBOL_GPL(cma_get_name);
static unsigned long cma_bitmap_aligned_mask(const struct cma *cma, unsigned int align_order) @@ -500,6 +502,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align, pr_debug("%s(): returned %p\n", __func__, page); return page; } +EXPORT_SYMBOL_GPL(cma_alloc);
/** * cma_release() - release allocated pages @@ -533,6 +536,7 @@ bool cma_release(struct cma *cma, const struct page *pages, unsigned int count)
return true; } +EXPORT_SYMBOL_GPL(cma_release);
int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data) { @@ -547,3 +551,4 @@ int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data)
return 0; } +EXPORT_SYMBOL_GPL(cma_for_each_area);
Allow loading system and cma heap as a module instead of just as a statically built in heap.
Since there isn't a good mechanism for dmabuf lifetime tracking it isn't safe to allow the heap drivers to be unloaded, so these drivers do not implement any module unloading functionality and will show up in lsmod as "[permanent]".
This patch also exports key functions from dmabuf heaps core and the heap helper functions so they can be accessed by the module.
Cc: Laura Abbott labbott@redhat.com Cc: Benjamin Gaignard benjamin.gaignard@linaro.org Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Pratik Patel pratikp@codeaurora.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Andrew F. Davis afd@ti.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Yue Hu huyue2@yulong.com Cc: Mike Rapoport rppt@linux.ibm.com Cc: Chenbo Feng fengc@google.com Cc: Alistair Strachan astrachan@google.com Cc: Sandeep Patil sspatil@google.com Cc: Hridya Valsaraju hridya@google.com Cc: dri-devel@lists.freedesktop.org Signed-off-by: John Stultz john.stultz@linaro.org --- drivers/dma-buf/dma-heap.c | 2 ++ drivers/dma-buf/heaps/Kconfig | 4 ++-- drivers/dma-buf/heaps/heap-helpers.c | 2 ++ 3 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c index 9a41b73e54b4..2c4ac71a715b 100644 --- a/drivers/dma-buf/dma-heap.c +++ b/drivers/dma-buf/dma-heap.c @@ -161,6 +161,7 @@ void *dma_heap_get_drvdata(struct dma_heap *heap) { return heap->priv; } +EXPORT_SYMBOL_GPL(dma_heap_get_drvdata);
struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info) { @@ -243,6 +244,7 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info) kfree(heap); return err_ret; } +EXPORT_SYMBOL_GPL(dma_heap_add);
static char *dma_heap_devnode(struct device *dev, umode_t *mode) { diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index a5eef06c4226..e273fb18feca 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -1,12 +1,12 @@ config DMABUF_HEAPS_SYSTEM - bool "DMA-BUF System Heap" + tristate "DMA-BUF System Heap" depends on DMABUF_HEAPS help Choose this option to enable the system dmabuf heap. The system heap is backed by pages from the buddy allocator. If in doubt, say Y.
config DMABUF_HEAPS_CMA - bool "DMA-BUF CMA Heap" + tristate "DMA-BUF CMA Heap" depends on DMABUF_HEAPS && DMA_CMA help Choose this option to enable dma-buf CMA heap. This heap is backed diff --git a/drivers/dma-buf/heaps/heap-helpers.c b/drivers/dma-buf/heaps/heap-helpers.c index 750bef4e902d..fb9835126893 100644 --- a/drivers/dma-buf/heaps/heap-helpers.c +++ b/drivers/dma-buf/heaps/heap-helpers.c @@ -24,6 +24,7 @@ void init_heap_helper_buffer(struct heap_helper_buffer *buffer, INIT_LIST_HEAD(&buffer->attachments); buffer->free = free; } +EXPORT_SYMBOL_GPL(init_heap_helper_buffer);
struct dma_buf *heap_helper_export_dmabuf(struct heap_helper_buffer *buffer, int fd_flags) @@ -37,6 +38,7 @@ struct dma_buf *heap_helper_export_dmabuf(struct heap_helper_buffer *buffer,
return dma_buf_export(&exp_info); } +EXPORT_SYMBOL_GPL(heap_helper_export_dmabuf);
static void *dma_heap_map_kernel(struct heap_helper_buffer *buffer) {
Hi John,
On Fri, Oct 25, 2019 at 11:48:34PM +0000, John Stultz wrote:
Allow loading system and cma heap as a module instead of just as a statically built in heap.
Since there isn't a good mechanism for dmabuf lifetime tracking it isn't safe to allow the heap drivers to be unloaded, so these drivers do not implement any module unloading functionality and will show up in lsmod as "[permanent]".
Cool, that alleviates my concerns :-)
This patch also exports key functions from dmabuf heaps core and the heap helper functions so they can be accessed by the module.
Cc: Laura Abbott labbott@redhat.com Cc: Benjamin Gaignard benjamin.gaignard@linaro.org Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Pratik Patel pratikp@codeaurora.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Andrew F. Davis afd@ti.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Yue Hu huyue2@yulong.com Cc: Mike Rapoport rppt@linux.ibm.com Cc: Chenbo Feng fengc@google.com Cc: Alistair Strachan astrachan@google.com Cc: Sandeep Patil sspatil@google.com Cc: Hridya Valsaraju hridya@google.com Cc: dri-devel@lists.freedesktop.org Signed-off-by: John Stultz john.stultz@linaro.org
drivers/dma-buf/dma-heap.c | 2 ++ drivers/dma-buf/heaps/Kconfig | 4 ++-- drivers/dma-buf/heaps/heap-helpers.c | 2 ++ 3 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c index 9a41b73e54b4..2c4ac71a715b 100644 --- a/drivers/dma-buf/dma-heap.c +++ b/drivers/dma-buf/dma-heap.c @@ -161,6 +161,7 @@ void *dma_heap_get_drvdata(struct dma_heap *heap) { return heap->priv; } +EXPORT_SYMBOL_GPL(dma_heap_get_drvdata);
struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info) { @@ -243,6 +244,7 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info) kfree(heap); return err_ret; } +EXPORT_SYMBOL_GPL(dma_heap_add);
Maybe overly picky - but adding the note about "no safe way to remove, so there's no dma_heap_remove" to a comment on this function may be easier to notice than in the git log alone.
Cheers, -Brian
static char *dma_heap_devnode(struct device *dev, umode_t *mode) { diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index a5eef06c4226..e273fb18feca 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -1,12 +1,12 @@ config DMABUF_HEAPS_SYSTEM
- bool "DMA-BUF System Heap"
- tristate "DMA-BUF System Heap" depends on DMABUF_HEAPS help Choose this option to enable the system dmabuf heap. The system heap is backed by pages from the buddy allocator. If in doubt, say Y.
config DMABUF_HEAPS_CMA
- bool "DMA-BUF CMA Heap"
- tristate "DMA-BUF CMA Heap" depends on DMABUF_HEAPS && DMA_CMA help Choose this option to enable dma-buf CMA heap. This heap is backed
diff --git a/drivers/dma-buf/heaps/heap-helpers.c b/drivers/dma-buf/heaps/heap-helpers.c index 750bef4e902d..fb9835126893 100644 --- a/drivers/dma-buf/heaps/heap-helpers.c +++ b/drivers/dma-buf/heaps/heap-helpers.c @@ -24,6 +24,7 @@ void init_heap_helper_buffer(struct heap_helper_buffer *buffer, INIT_LIST_HEAD(&buffer->attachments); buffer->free = free; } +EXPORT_SYMBOL_GPL(init_heap_helper_buffer);
struct dma_buf *heap_helper_export_dmabuf(struct heap_helper_buffer *buffer, int fd_flags) @@ -37,6 +38,7 @@ struct dma_buf *heap_helper_export_dmabuf(struct heap_helper_buffer *buffer,
return dma_buf_export(&exp_info); } +EXPORT_SYMBOL_GPL(heap_helper_export_dmabuf);
static void *dma_heap_map_kernel(struct heap_helper_buffer *buffer) { -- 2.17.1
On Fri, Oct 25, 2019 at 11:48:34PM +0000, John Stultz wrote:
Allow loading system and cma heap as a module instead of just as a statically built in heap.
Since there isn't a good mechanism for dmabuf lifetime tracking it isn't safe to allow the heap drivers to be unloaded, so these drivers do not implement any module unloading functionality and will show up in lsmod as "[permanent]".
dma-buf itself has all the try_module_get we'll need ... why is this not possible? -Daniel
This patch also exports key functions from dmabuf heaps core and the heap helper functions so they can be accessed by the module.
Cc: Laura Abbott labbott@redhat.com Cc: Benjamin Gaignard benjamin.gaignard@linaro.org Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Pratik Patel pratikp@codeaurora.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Andrew F. Davis afd@ti.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Yue Hu huyue2@yulong.com Cc: Mike Rapoport rppt@linux.ibm.com Cc: Chenbo Feng fengc@google.com Cc: Alistair Strachan astrachan@google.com Cc: Sandeep Patil sspatil@google.com Cc: Hridya Valsaraju hridya@google.com Cc: dri-devel@lists.freedesktop.org Signed-off-by: John Stultz john.stultz@linaro.org
drivers/dma-buf/dma-heap.c | 2 ++ drivers/dma-buf/heaps/Kconfig | 4 ++-- drivers/dma-buf/heaps/heap-helpers.c | 2 ++ 3 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c index 9a41b73e54b4..2c4ac71a715b 100644 --- a/drivers/dma-buf/dma-heap.c +++ b/drivers/dma-buf/dma-heap.c @@ -161,6 +161,7 @@ void *dma_heap_get_drvdata(struct dma_heap *heap) { return heap->priv; } +EXPORT_SYMBOL_GPL(dma_heap_get_drvdata);
struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info) { @@ -243,6 +244,7 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info) kfree(heap); return err_ret; } +EXPORT_SYMBOL_GPL(dma_heap_add);
static char *dma_heap_devnode(struct device *dev, umode_t *mode) { diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index a5eef06c4226..e273fb18feca 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -1,12 +1,12 @@ config DMABUF_HEAPS_SYSTEM
- bool "DMA-BUF System Heap"
- tristate "DMA-BUF System Heap" depends on DMABUF_HEAPS help Choose this option to enable the system dmabuf heap. The system heap is backed by pages from the buddy allocator. If in doubt, say Y.
config DMABUF_HEAPS_CMA
- bool "DMA-BUF CMA Heap"
- tristate "DMA-BUF CMA Heap" depends on DMABUF_HEAPS && DMA_CMA help Choose this option to enable dma-buf CMA heap. This heap is backed
diff --git a/drivers/dma-buf/heaps/heap-helpers.c b/drivers/dma-buf/heaps/heap-helpers.c index 750bef4e902d..fb9835126893 100644 --- a/drivers/dma-buf/heaps/heap-helpers.c +++ b/drivers/dma-buf/heaps/heap-helpers.c @@ -24,6 +24,7 @@ void init_heap_helper_buffer(struct heap_helper_buffer *buffer, INIT_LIST_HEAD(&buffer->attachments); buffer->free = free; } +EXPORT_SYMBOL_GPL(init_heap_helper_buffer);
struct dma_buf *heap_helper_export_dmabuf(struct heap_helper_buffer *buffer, int fd_flags) @@ -37,6 +38,7 @@ struct dma_buf *heap_helper_export_dmabuf(struct heap_helper_buffer *buffer,
return dma_buf_export(&exp_info); } +EXPORT_SYMBOL_GPL(heap_helper_export_dmabuf);
static void *dma_heap_map_kernel(struct heap_helper_buffer *buffer) { -- 2.17.1
dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
On Mon, Nov 4, 2019 at 2:24 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:34PM +0000, John Stultz wrote:
Allow loading system and cma heap as a module instead of just as a statically built in heap.
Since there isn't a good mechanism for dmabuf lifetime tracking it isn't safe to allow the heap drivers to be unloaded, so these drivers do not implement any module unloading functionality and will show up in lsmod as "[permanent]".
dma-buf itself has all the try_module_get we'll need ... why is this not possible?
Let me look into that. Thanks for the pointer.
thanks -john
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
Now that the DMA BUF heaps core code has been queued, I wanted to send out some of the pending changes that I've been working on.
For use with Android and their GKI effort, it is desired that DMA BUF heaps are able to be loaded as modules. This is required for migrating vendors off of ION which was also recently changed to support modules.
So this patch series simply provides the necessary exported symbols and allows the system and CMA drivers to be built as modules.
Due to the fact that dmabuf's allocated from a heap may be in use for quite some time, there isn't a way to safely unload the driver once it has been loaded. Thus these drivers do no implement module_exit() functions and will show up in lsmod as "[permanent]"
Feedback and thoughts on this would be greatly appreciated!
Do we actually want this?
I figured if we just state that vendors should set up all the right dma-buf heaps in dt, is that not enough?
Exporting symbols for no real in-tree users feels fishy. -Daniel
thanks -john
Cc: Laura Abbott labbott@redhat.com Cc: Benjamin Gaignard benjamin.gaignard@linaro.org Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Pratik Patel pratikp@codeaurora.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Andrew F. Davis afd@ti.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Yue Hu huyue2@yulong.com Cc: Mike Rapoport rppt@linux.ibm.com Cc: Chenbo Feng fengc@google.com Cc: Alistair Strachan astrachan@google.com Cc: Sandeep Patil sspatil@google.com Cc: Hridya Valsaraju hridya@google.com Cc: dri-devel@lists.freedesktop.org
John Stultz (1): dma-buf: heaps: Allow system & cma heaps to be configured as a modules
Sandeep Patil (1): mm: cma: Export cma symbols for cma heap as a module
drivers/dma-buf/dma-heap.c | 2 ++ drivers/dma-buf/heaps/Kconfig | 4 ++-- drivers/dma-buf/heaps/heap-helpers.c | 2 ++ kernel/dma/contiguous.c | 1 + mm/cma.c | 5 +++++ 5 files changed, 12 insertions(+), 2 deletions(-)
-- 2.17.1
dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
On Mon, Nov 4, 2019 at 1:58 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
Now that the DMA BUF heaps core code has been queued, I wanted to send out some of the pending changes that I've been working on.
For use with Android and their GKI effort, it is desired that DMA BUF heaps are able to be loaded as modules. This is required for migrating vendors off of ION which was also recently changed to support modules.
So this patch series simply provides the necessary exported symbols and allows the system and CMA drivers to be built as modules.
Due to the fact that dmabuf's allocated from a heap may be in use for quite some time, there isn't a way to safely unload the driver once it has been loaded. Thus these drivers do no implement module_exit() functions and will show up in lsmod as "[permanent]"
Feedback and thoughts on this would be greatly appreciated!
Do we actually want this?
I guess that always depends on the definition of "we" :)
I figured if we just state that vendors should set up all the right dma-buf heaps in dt, is that not enough?
So even if the heaps are configured via DT (which at the moment there is no such binding, so that's not really a valid method yet), there's still the question of if the heap is necessary/makes sense on the device. And the DT would only control the availability of the heap interface, not if the heap driver is loaded or not.
On the HiKey/HiKey960 boards, we have to allocate contiguous buffers for the display framebuffer. So gralloc uses ION to allocate from the CMA heap. However on the db845c, it has no such restrictions, so the CMA heap isn't necessary.
With Android's GKI effort, there needs to be one kernel that works on all the devices, and they are using modules to try to minimize the amount of memory spent on functionality that isn't universally needed. So on devices that don't need the CMA heap, they'd probably prefer not to load the CMA dmabuf heap driver, so it would be best if it could be built as a module. If we want to build the CMA heap as a module, the symbols it uses need to be exported.
Exporting symbols for no real in-tree users feels fishy.
I'm submitting an in-tree user here. So I'm not sure what you mean? I suspect you're thinking there is some hidden/nefarious plan here, but really there isn't.
thanks -john
On Mon, Nov 04, 2019 at 10:57:44AM -0800, John Stultz wrote:
On Mon, Nov 4, 2019 at 1:58 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
Now that the DMA BUF heaps core code has been queued, I wanted to send out some of the pending changes that I've been working on.
For use with Android and their GKI effort, it is desired that DMA BUF heaps are able to be loaded as modules. This is required for migrating vendors off of ION which was also recently changed to support modules.
So this patch series simply provides the necessary exported symbols and allows the system and CMA drivers to be built as modules.
Due to the fact that dmabuf's allocated from a heap may be in use for quite some time, there isn't a way to safely unload the driver once it has been loaded. Thus these drivers do no implement module_exit() functions and will show up in lsmod as "[permanent]"
Feedback and thoughts on this would be greatly appreciated!
Do we actually want this?
I guess that always depends on the definition of "we" :)
I figured if we just state that vendors should set up all the right dma-buf heaps in dt, is that not enough?
So even if the heaps are configured via DT (which at the moment there is no such binding, so that's not really a valid method yet), there's still the question of if the heap is necessary/makes sense on the device. And the DT would only control the availability of the heap interface, not if the heap driver is loaded or not.
Hm I thought the cma regions are configured in DT? How does that work if it's not using DT?
On the HiKey/HiKey960 boards, we have to allocate contiguous buffers for the display framebuffer. So gralloc uses ION to allocate from the CMA heap. However on the db845c, it has no such restrictions, so the CMA heap isn't necessary.
Why do you have a CMA region for the 2nd board if you don't need it? _That_ sounds like some serious memory waster, not a few lines of code loaded for nothing :-)
With Android's GKI effort, there needs to be one kernel that works on all the devices, and they are using modules to try to minimize the amount of memory spent on functionality that isn't universally needed. So on devices that don't need the CMA heap, they'd probably prefer not to load the CMA dmabuf heap driver, so it would be best if it could be built as a module. If we want to build the CMA heap as a module, the symbols it uses need to be exported.
Yeah, I guess I'm disagreeing on whether dma-buf heaps are core or not.
Exporting symbols for no real in-tree users feels fishy.
I'm submitting an in-tree user here. So I'm not sure what you mean? I suspect you're thinking there is some hidden/nefarious plan here, but really there isn't.
I was working under the assumption that you're only exporting the symbols for other heaps, and keep the current ones in-tree. Are there even any out-of-tree dma-buf heaps still? out-of-tree and legit different use-case I mean ofc, not just out-of-tree because inertia :-) -Daniel
On 11/5/19 4:42 AM, Daniel Vetter wrote:
On Mon, Nov 04, 2019 at 10:57:44AM -0800, John Stultz wrote:
On Mon, Nov 4, 2019 at 1:58 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
Now that the DMA BUF heaps core code has been queued, I wanted to send out some of the pending changes that I've been working on.
For use with Android and their GKI effort, it is desired that DMA BUF heaps are able to be loaded as modules. This is required for migrating vendors off of ION which was also recently changed to support modules.
So this patch series simply provides the necessary exported symbols and allows the system and CMA drivers to be built as modules.
Due to the fact that dmabuf's allocated from a heap may be in use for quite some time, there isn't a way to safely unload the driver once it has been loaded. Thus these drivers do no implement module_exit() functions and will show up in lsmod as "[permanent]"
Feedback and thoughts on this would be greatly appreciated!
Do we actually want this?
I guess that always depends on the definition of "we" :)
I figured if we just state that vendors should set up all the right dma-buf heaps in dt, is that not enough?
So even if the heaps are configured via DT (which at the moment there is no such binding, so that's not really a valid method yet), there's still the question of if the heap is necessary/makes sense on the device. And the DT would only control the availability of the heap interface, not if the heap driver is loaded or not.
Hm I thought the cma regions are configured in DT? How does that work if it's not using DT?
On the HiKey/HiKey960 boards, we have to allocate contiguous buffers for the display framebuffer. So gralloc uses ION to allocate from the CMA heap. However on the db845c, it has no such restrictions, so the CMA heap isn't necessary.
Why do you have a CMA region for the 2nd board if you don't need it? _That_ sounds like some serious memory waster, not a few lines of code loaded for nothing :-)
With Android's GKI effort, there needs to be one kernel that works on all the devices, and they are using modules to try to minimize the amount of memory spent on functionality that isn't universally needed. So on devices that don't need the CMA heap, they'd probably prefer not to load the CMA dmabuf heap driver, so it would be best if it could be built as a module. If we want to build the CMA heap as a module, the symbols it uses need to be exported.
Yeah, I guess I'm disagreeing on whether dma-buf heaps are core or not.
Exporting symbols for no real in-tree users feels fishy.
I'm submitting an in-tree user here. So I'm not sure what you mean? I suspect you're thinking there is some hidden/nefarious plan here, but really there isn't.
I was working under the assumption that you're only exporting the symbols for other heaps, and keep the current ones in-tree. Are there even any out-of-tree dma-buf heaps still? out-of-tree and legit different use-case I mean ofc, not just out-of-tree because inertia :-)
Not sure what you mean here, hopefully all the heaps can be "in-tree" some day.
https://patchwork.kernel.org/patch/10863957/
Plus some non-caching heaps and one that forces early allocation of our PAT (gart like) IP.
All this stuff is going into our evil vendor tree next cycle (if not upstream by then :)), if we want some of these "specialty" heaps to go into generic kernel builds at some point they will need to be modules if the core is.
Although I am still thinking Heaps should be always built in + system + CMA heaps, then the rando heaps could be modules if needed.
Andrew
-Daniel
On Tue, Nov 5, 2019 at 2:30 PM Andrew F. Davis afd@ti.com wrote:
On 11/5/19 4:42 AM, Daniel Vetter wrote:
On Mon, Nov 04, 2019 at 10:57:44AM -0800, John Stultz wrote:
On Mon, Nov 4, 2019 at 1:58 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
Now that the DMA BUF heaps core code has been queued, I wanted to send out some of the pending changes that I've been working on.
For use with Android and their GKI effort, it is desired that DMA BUF heaps are able to be loaded as modules. This is required for migrating vendors off of ION which was also recently changed to support modules.
So this patch series simply provides the necessary exported symbols and allows the system and CMA drivers to be built as modules.
Due to the fact that dmabuf's allocated from a heap may be in use for quite some time, there isn't a way to safely unload the driver once it has been loaded. Thus these drivers do no implement module_exit() functions and will show up in lsmod as "[permanent]"
Feedback and thoughts on this would be greatly appreciated!
Do we actually want this?
I guess that always depends on the definition of "we" :)
I figured if we just state that vendors should set up all the right dma-buf heaps in dt, is that not enough?
So even if the heaps are configured via DT (which at the moment there is no such binding, so that's not really a valid method yet), there's still the question of if the heap is necessary/makes sense on the device. And the DT would only control the availability of the heap interface, not if the heap driver is loaded or not.
Hm I thought the cma regions are configured in DT? How does that work if it's not using DT?
On the HiKey/HiKey960 boards, we have to allocate contiguous buffers for the display framebuffer. So gralloc uses ION to allocate from the CMA heap. However on the db845c, it has no such restrictions, so the CMA heap isn't necessary.
Why do you have a CMA region for the 2nd board if you don't need it? _That_ sounds like some serious memory waster, not a few lines of code loaded for nothing :-)
With Android's GKI effort, there needs to be one kernel that works on all the devices, and they are using modules to try to minimize the amount of memory spent on functionality that isn't universally needed. So on devices that don't need the CMA heap, they'd probably prefer not to load the CMA dmabuf heap driver, so it would be best if it could be built as a module. If we want to build the CMA heap as a module, the symbols it uses need to be exported.
Yeah, I guess I'm disagreeing on whether dma-buf heaps are core or not.
Exporting symbols for no real in-tree users feels fishy.
I'm submitting an in-tree user here. So I'm not sure what you mean? I suspect you're thinking there is some hidden/nefarious plan here, but really there isn't.
I was working under the assumption that you're only exporting the symbols for other heaps, and keep the current ones in-tree. Are there even any out-of-tree dma-buf heaps still? out-of-tree and legit different use-case I mean ofc, not just out-of-tree because inertia :-)
Not sure what you mean here, hopefully all the heaps can be "in-tree" some day.
No idea this is good or bad, where's the userspace for it?
Plus some non-caching heaps and one that forces early allocation of our PAT (gart like) IP.
Hm, so essentially we'd need to move _all_ drm allocators into dma-buf heaps, for all drivers? Can't just do this for TI only ...
All this stuff is going into our evil vendor tree next cycle (if not upstream by then :)), if we want some of these "specialty" heaps to go into generic kernel builds at some point they will need to be modules if the core is.
Although I am still thinking Heaps should be always built in + system + CMA heaps, then the rando heaps could be modules if needed.
Yeah that's what I'd expected to happen. Speciality heaps for when you have the relevant something unusual (and I'm not sure whether upstream does want something unusual really, the above examples from you sound a bit strange). -Daniel
On Tue, Nov 5, 2019 at 1:43 AM Daniel Vetter daniel@ffwll.ch wrote:
On Mon, Nov 04, 2019 at 10:57:44AM -0800, John Stultz wrote:
On Mon, Nov 4, 2019 at 1:58 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
So even if the heaps are configured via DT (which at the moment there is no such binding, so that's not really a valid method yet), there's still the question of if the heap is necessary/makes sense on the device. And the DT would only control the availability of the heap interface, not if the heap driver is loaded or not.
Hm I thought the cma regions are configured in DT? How does that work if it's not using DT?
So yea, CMA regions are either configured by DT or setup at build time (I think there's a cmdline option to set it up as well).
But the CMA regions and the dmabuf cma heap driver are separate things. The latter uses the former.
On the HiKey/HiKey960 boards, we have to allocate contiguous buffers for the display framebuffer. So gralloc uses ION to allocate from the CMA heap. However on the db845c, it has no such restrictions, so the CMA heap isn't necessary.
Why do you have a CMA region for the 2nd board if you don't need it? _That_ sounds like some serious memory waster, not a few lines of code loaded for nothing :-)
??? That's not what I said above. If the db845c doesn't need CMA it won't have a CMA region.
The issue at hand is that we may want to avoid loading the dmabuf CMA heap driver on a board that doesn't use CMA.
With Android's GKI effort, there needs to be one kernel that works on all the devices, and they are using modules to try to minimize the amount of memory spent on functionality that isn't universally needed. So on devices that don't need the CMA heap, they'd probably prefer not to load the CMA dmabuf heap driver, so it would be best if it could be built as a module. If we want to build the CMA heap as a module, the symbols it uses need to be exported.
Yeah, I guess I'm disagreeing on whether dma-buf heaps are core or not.
That's fine to dispute. I'm not really in a place to assert one way or not, but the Android folks have made their ION system and CMA heaps loadable via a module, so it would seem like having the dmabuf system and CMA heaps be modular would be useful to properly replace that usage.
For instance, the system heap as a module probably doesn't make much sense, as most boards that want to use the dmabuf heaps interface are likely to use that as well. CMA is more optional as not all boards will use that one, so it might make sense to avoid loading it.
Sandeep: Can you chime in here as to how critical having the system and cma heaps be modules are?
Exporting symbols for no real in-tree users feels fishy.
I'm submitting an in-tree user here. So I'm not sure what you mean? I suspect you're thinking there is some hidden/nefarious plan here, but really there isn't.
I was working under the assumption that you're only exporting the symbols for other heaps, and keep the current ones in-tree.
No. I'm trying to allow the (hopefully-soon-to-be-in-tree) system and cma heap drivers to be loaded from a module. If other heaps need exports, they can submit their heaps upstream and argue for the exported symbols themselves.
Are there even any out-of-tree dma-buf heaps still? out-of-tree and legit different use-case I mean ofc, not just out-of-tree because inertia :-)
So as Andrew mentioned, he has some dmabuf heaps he's working on at TI. From what I've heard the qualcomm folks like the dmabuf heaps approach, but I'm not sure if they've taken a pass at converting their vendor ION heaps to it yet.
The main reason I'm only submitting system and CMA is because those are the only two I personally have a user for (HiKey/HiKey960 boards). It's my hope that once we deprecate ION in Android, vendors will migrate and we'll be able to push them to upstream their heaps as well.
thanks -john
On Tue, Nov 5, 2019 at 6:41 PM John Stultz john.stultz@linaro.org wrote:
On Tue, Nov 5, 2019 at 1:43 AM Daniel Vetter daniel@ffwll.ch wrote:
On Mon, Nov 04, 2019 at 10:57:44AM -0800, John Stultz wrote:
On Mon, Nov 4, 2019 at 1:58 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
So even if the heaps are configured via DT (which at the moment there is no such binding, so that's not really a valid method yet), there's still the question of if the heap is necessary/makes sense on the device. And the DT would only control the availability of the heap interface, not if the heap driver is loaded or not.
Hm I thought the cma regions are configured in DT? How does that work if it's not using DT?
So yea, CMA regions are either configured by DT or setup at build time (I think there's a cmdline option to set it up as well).
But the CMA regions and the dmabuf cma heap driver are separate things. The latter uses the former.
Huh, I assumed the plan is that whenever there's a cma region, we want to instantiate a dma-buf heap for it? Why/when would we not want to do that?
On the HiKey/HiKey960 boards, we have to allocate contiguous buffers for the display framebuffer. So gralloc uses ION to allocate from the CMA heap. However on the db845c, it has no such restrictions, so the CMA heap isn't necessary.
Why do you have a CMA region for the 2nd board if you don't need it? _That_ sounds like some serious memory waster, not a few lines of code loaded for nothing :-)
??? That's not what I said above. If the db845c doesn't need CMA it won't have a CMA region.
The issue at hand is that we may want to avoid loading the dmabuf CMA heap driver on a board that doesn't use CMA.
So the CMA core code is also a module, or how does that work? Not loading the cma dma-buf heap, but keeping all the other cma code around feels slightly silly. Do we have numbers that justify this silliness?
With Android's GKI effort, there needs to be one kernel that works on all the devices, and they are using modules to try to minimize the amount of memory spent on functionality that isn't universally needed. So on devices that don't need the CMA heap, they'd probably prefer not to load the CMA dmabuf heap driver, so it would be best if it could be built as a module. If we want to build the CMA heap as a module, the symbols it uses need to be exported.
Yeah, I guess I'm disagreeing on whether dma-buf heaps are core or not.
That's fine to dispute. I'm not really in a place to assert one way or not, but the Android folks have made their ION system and CMA heaps loadable via a module, so it would seem like having the dmabuf system and CMA heaps be modular would be useful to properly replace that usage.
For instance, the system heap as a module probably doesn't make much sense, as most boards that want to use the dmabuf heaps interface are likely to use that as well. CMA is more optional as not all boards will use that one, so it might make sense to avoid loading it.
Sandeep: Can you chime in here as to how critical having the system and cma heaps be modules are?
Exporting symbols for no real in-tree users feels fishy.
I'm submitting an in-tree user here. So I'm not sure what you mean? I suspect you're thinking there is some hidden/nefarious plan here, but really there isn't.
I was working under the assumption that you're only exporting the symbols for other heaps, and keep the current ones in-tree.
No. I'm trying to allow the (hopefully-soon-to-be-in-tree) system and cma heap drivers to be loaded from a module. If other heaps need exports, they can submit their heaps upstream and argue for the exported symbols themselves.
Are there even any out-of-tree dma-buf heaps still? out-of-tree and legit different use-case I mean ofc, not just out-of-tree because inertia :-)
So as Andrew mentioned, he has some dmabuf heaps he's working on at TI. From what I've heard the qualcomm folks like the dmabuf heaps approach, but I'm not sure if they've taken a pass at converting their vendor ION heaps to it yet.
The main reason I'm only submitting system and CMA is because those are the only two I personally have a user for (HiKey/HiKey960 boards). It's my hope that once we deprecate ION in Android, vendors will migrate and we'll be able to push them to upstream their heaps as well.
I think for upstream I'd want to see those other heaps first. If they're mostly driver allocators exposed as heaps, then I think we need something different than heap modules, maybe allow dma-buf to allocate from drivers instead. But afaiui all such driver allocators we have in upstream are cma regions only right now. -Daniel
On Tue, Nov 5, 2019 at 11:19 AM Daniel Vetter daniel@ffwll.ch wrote:
On Tue, Nov 5, 2019 at 6:41 PM John Stultz john.stultz@linaro.org wrote:
On Tue, Nov 5, 2019 at 1:43 AM Daniel Vetter daniel@ffwll.ch wrote:
On Mon, Nov 04, 2019 at 10:57:44AM -0800, John Stultz wrote:
On Mon, Nov 4, 2019 at 1:58 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
So even if the heaps are configured via DT (which at the moment there is no such binding, so that's not really a valid method yet), there's still the question of if the heap is necessary/makes sense on the device. And the DT would only control the availability of the heap interface, not if the heap driver is loaded or not.
Hm I thought the cma regions are configured in DT? How does that work if it's not using DT?
So yea, CMA regions are either configured by DT or setup at build time (I think there's a cmdline option to set it up as well).
But the CMA regions and the dmabuf cma heap driver are separate things. The latter uses the former.
Huh, I assumed the plan is that whenever there's a cma region, we want to instantiate a dma-buf heap for it? Why/when would we not want to do that?
Not quite. Andrew noted that we may not want to expose all CMA regions via dmabuf heaps, so right now we only expose the default region. I have follow on patches that I sent out earlier (which requires a to-be-finalized DT binding) which allows us to specify which other CMA regions to expose.
On the HiKey/HiKey960 boards, we have to allocate contiguous buffers for the display framebuffer. So gralloc uses ION to allocate from the CMA heap. However on the db845c, it has no such restrictions, so the CMA heap isn't necessary.
Why do you have a CMA region for the 2nd board if you don't need it? _That_ sounds like some serious memory waster, not a few lines of code loaded for nothing :-)
??? That's not what I said above. If the db845c doesn't need CMA it won't have a CMA region.
The issue at hand is that we may want to avoid loading the dmabuf CMA heap driver on a board that doesn't use CMA.
So the CMA core code is also a module, or how does that work? Not
No. CMA core isn't available as a module.
loading the cma dma-buf heap, but keeping all the other cma code around feels slightly silly. Do we have numbers that justify this silliness?
I agree that is maybe not the most critical item on the list, but its one of many that do add up over time.
Again, I'll defer to Sandeep or other folks on the Google side to help with the importance here. Mostly I'm trying to ensure there is functional parity to ION so we don't give folks any reason they could object to deprecating it.
The main reason I'm only submitting system and CMA is because those are the only two I personally have a user for (HiKey/HiKey960 boards). It's my hope that once we deprecate ION in Android, vendors will migrate and we'll be able to push them to upstream their heaps as well.
I think for upstream I'd want to see those other heaps first. If they're mostly driver allocators exposed as heaps, then I think we need something different than heap modules, maybe allow dma-buf to allocate from drivers instead. But afaiui all such driver allocators we have in upstream are cma regions only right now.
I'm sorry, I'm not sure I understand what you mean here (I'm not sure what action I should be taking). Could you clarify this point?
thanks -john
On Tue, Nov 5, 2019 at 8:48 PM John Stultz john.stultz@linaro.org wrote:
On Tue, Nov 5, 2019 at 11:19 AM Daniel Vetter daniel@ffwll.ch wrote:
On Tue, Nov 5, 2019 at 6:41 PM John Stultz john.stultz@linaro.org wrote:
On Tue, Nov 5, 2019 at 1:43 AM Daniel Vetter daniel@ffwll.ch wrote:
On Mon, Nov 04, 2019 at 10:57:44AM -0800, John Stultz wrote:
On Mon, Nov 4, 2019 at 1:58 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
So even if the heaps are configured via DT (which at the moment there is no such binding, so that's not really a valid method yet), there's still the question of if the heap is necessary/makes sense on the device. And the DT would only control the availability of the heap interface, not if the heap driver is loaded or not.
Hm I thought the cma regions are configured in DT? How does that work if it's not using DT?
So yea, CMA regions are either configured by DT or setup at build time (I think there's a cmdline option to set it up as well).
But the CMA regions and the dmabuf cma heap driver are separate things. The latter uses the former.
Huh, I assumed the plan is that whenever there's a cma region, we want to instantiate a dma-buf heap for it? Why/when would we not want to do that?
Not quite. Andrew noted that we may not want to expose all CMA regions via dmabuf heaps, so right now we only expose the default region. I have follow on patches that I sent out earlier (which requires a to-be-finalized DT binding) which allows us to specify which other CMA regions to expose.
Why do we not want to expose them all? I figured if there's a cma heap, then a device you have needs it, and if that's the case you might want to allocate for that device from the heap? Maybe link to the discussion?
On the HiKey/HiKey960 boards, we have to allocate contiguous buffers for the display framebuffer. So gralloc uses ION to allocate from the CMA heap. However on the db845c, it has no such restrictions, so the CMA heap isn't necessary.
Why do you have a CMA region for the 2nd board if you don't need it? _That_ sounds like some serious memory waster, not a few lines of code loaded for nothing :-)
??? That's not what I said above. If the db845c doesn't need CMA it won't have a CMA region.
The issue at hand is that we may want to avoid loading the dmabuf CMA heap driver on a board that doesn't use CMA.
So the CMA core code is also a module, or how does that work? Not
No. CMA core isn't available as a module.
loading the cma dma-buf heap, but keeping all the other cma code around feels slightly silly. Do we have numbers that justify this silliness?
I agree that is maybe not the most critical item on the list, but its one of many that do add up over time.
Again, I'll defer to Sandeep or other folks on the Google side to help with the importance here. Mostly I'm trying to ensure there is functional parity to ION so we don't give folks any reason they could object to deprecating it.
The main reason I'm only submitting system and CMA is because those are the only two I personally have a user for (HiKey/HiKey960 boards). It's my hope that once we deprecate ION in Android, vendors will migrate and we'll be able to push them to upstream their heaps as well.
I think for upstream I'd want to see those other heaps first. If they're mostly driver allocators exposed as heaps, then I think we need something different than heap modules, maybe allow dma-buf to allocate from drivers instead. But afaiui all such driver allocators we have in upstream are cma regions only right now.
I'm sorry, I'm not sure I understand what you mean here (I'm not sure what action I should be taking). Could you clarify this point?
I'm not sold on the use-case for this, but maybe if I see the actual use-cases I might be swayed. A very basic/minimal "register a new dma-buf heap" function should be all that's really needed for android, so maybe we can start with that? -Daniel
On Tue, Nov 05, 2019 at 11:47:53AM -0800, John Stultz wrote:
On Tue, Nov 5, 2019 at 11:19 AM Daniel Vetter daniel@ffwll.ch wrote:
On Tue, Nov 5, 2019 at 6:41 PM John Stultz john.stultz@linaro.org wrote:
On Tue, Nov 5, 2019 at 1:43 AM Daniel Vetter daniel@ffwll.ch wrote:
On Mon, Nov 04, 2019 at 10:57:44AM -0800, John Stultz wrote:
On Mon, Nov 4, 2019 at 1:58 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
So even if the heaps are configured via DT (which at the moment there is no such binding, so that's not really a valid method yet), there's still the question of if the heap is necessary/makes sense on the device. And the DT would only control the availability of the heap interface, not if the heap driver is loaded or not.
Hm I thought the cma regions are configured in DT? How does that work if it's not using DT?
So yea, CMA regions are either configured by DT or setup at build time (I think there's a cmdline option to set it up as well).
But the CMA regions and the dmabuf cma heap driver are separate things. The latter uses the former.
Huh, I assumed the plan is that whenever there's a cma region, we want to instantiate a dma-buf heap for it? Why/when would we not want to do that?
Not quite. Andrew noted that we may not want to expose all CMA regions via dmabuf heaps, so right now we only expose the default region. I have follow on patches that I sent out earlier (which requires a to-be-finalized DT binding) which allows us to specify which other CMA regions to expose.
On the HiKey/HiKey960 boards, we have to allocate contiguous buffers for the display framebuffer. So gralloc uses ION to allocate from the CMA heap. However on the db845c, it has no such restrictions, so the CMA heap isn't necessary.
Why do you have a CMA region for the 2nd board if you don't need it? _That_ sounds like some serious memory waster, not a few lines of code loaded for nothing :-)
??? That's not what I said above. If the db845c doesn't need CMA it won't have a CMA region.
The issue at hand is that we may want to avoid loading the dmabuf CMA heap driver on a board that doesn't use CMA.
So the CMA core code is also a module, or how does that work? Not
No. CMA core isn't available as a module.
loading the cma dma-buf heap, but keeping all the other cma code around feels slightly silly. Do we have numbers that justify this silliness?
I agree that is maybe not the most critical item on the list, but its one of many that do add up over time.
Again, I'll defer to Sandeep or other folks on the Google side to help with the importance here. Mostly I'm trying to ensure there is functional parity to ION so we don't give folks any reason they could object to deprecating it.
Parity with ION will definitely be nice. For now, however, even if we achieve that parity with UAPI and think about the cma-heap-as-module bit later, I guess that's ok.
The real problem is the need for these heaps to be a module in the first place. I'd much rather have an upstream user to show the need for cache maintenance operations that have been talked about so many times, so we can make them happen for dma-buf-heaps in upstream. None of this has to be a module if that happens :(.
The reason for the "modularization" for ion heaps is also the CMOs for Android use cases. Unfortunately we haven't had any luck with proving the need for. John, CMIIW.
- ssp
On Tue, Nov 05, 2019 at 09:41:44AM -0800, John Stultz wrote:
On Tue, Nov 5, 2019 at 1:43 AM Daniel Vetter daniel@ffwll.ch wrote:
On Mon, Nov 04, 2019 at 10:57:44AM -0800, John Stultz wrote:
On Mon, Nov 4, 2019 at 1:58 AM Daniel Vetter daniel@ffwll.ch wrote:
On Fri, Oct 25, 2019 at 11:48:32PM +0000, John Stultz wrote:
So even if the heaps are configured via DT (which at the moment there is no such binding, so that's not really a valid method yet), there's still the question of if the heap is necessary/makes sense on the device. And the DT would only control the availability of the heap interface, not if the heap driver is loaded or not.
Hm I thought the cma regions are configured in DT? How does that work if it's not using DT?
So yea, CMA regions are either configured by DT or setup at build time (I think there's a cmdline option to set it up as well).
But the CMA regions and the dmabuf cma heap driver are separate things. The latter uses the former.
On the HiKey/HiKey960 boards, we have to allocate contiguous buffers for the display framebuffer. So gralloc uses ION to allocate from the CMA heap. However on the db845c, it has no such restrictions, so the CMA heap isn't necessary.
Why do you have a CMA region for the 2nd board if you don't need it? _That_ sounds like some serious memory waster, not a few lines of code loaded for nothing :-)
??? That's not what I said above. If the db845c doesn't need CMA it won't have a CMA region.
The issue at hand is that we may want to avoid loading the dmabuf CMA heap driver on a board that doesn't use CMA.
With Android's GKI effort, there needs to be one kernel that works on all the devices, and they are using modules to try to minimize the amount of memory spent on functionality that isn't universally needed. So on devices that don't need the CMA heap, they'd probably prefer not to load the CMA dmabuf heap driver, so it would be best if it could be built as a module. If we want to build the CMA heap as a module, the symbols it uses need to be exported.
Yeah, I guess I'm disagreeing on whether dma-buf heaps are core or not.
That's fine to dispute. I'm not really in a place to assert one way or not, but the Android folks have made their ION system and CMA heaps loadable via a module, so it would seem like having the dmabuf system and CMA heaps be modular would be useful to properly replace that usage.
For instance, the system heap as a module probably doesn't make much sense, as most boards that want to use the dmabuf heaps interface are likely to use that as well. CMA is more optional as not all boards will use that one, so it might make sense to avoid loading it.
Sandeep: Can you chime in here as to how critical having the system and cma heaps be modules are?
With ion, we are making sure there are *standard* heaps that Android should be able to rely on to exist in all kernels [1]. That list is based on what default heaps ion had out-of-tree.
As of today, even from those that ion had, Android vendor independent code only relies on 'system heap' and 'cma/dma heaps' so, can safely ignore the carveout and other ion heaps.
system heap is really the one that is realistically 'hardware independent', so that can be in kernel. The cma heaps and their existence is optional, so it will be nice to be able to load them as modules.
<snip>
- ssp
1. https://android.googlesource.com/platform/system/core/+/refs/heads/master/li...
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