Re: [PATCH v3 5/6] iommu/rockchip: use DMA API to map, to flush cache

Hi Shunqian,

On Wed, Jun 15, 2016 at 9:04 PM, Shunqian Zheng zhengsq@rock-chips.com wrote:

Use DMA API instead of architecture internal functions like __cpuc_flush_dcache_area() etc.

To support the virtual device like DRM the virtual slave iommu added in the previous patch, attaching to which the DRM can use it own domain->dev for dma_map_*(), dma_sync_*() even VOP is disabled.

With this patch, this driver is available for ARM64 like RK3399.

Signed-off-by: Shunqian Zheng zhengsq@rock-chips.com

drivers/iommu/rockchip-iommu.c | 113 +++++++++++++++++++++++++++-------------- 1 file changed, 76 insertions(+), 37 deletions(-)

In general looks good to me, but still have some concern about attaching and detaching. Please see inline.

diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c index 82ecc99..b60b29e 100644 --- a/drivers/iommu/rockchip-iommu.c +++ b/drivers/iommu/rockchip-iommu.c

[snip]

@@ -886,6 +901,22 @@ static int rk_iommu_attach_device(struct iommu_domain *domain, return -ENOMEM; }

•   /* Set the domain dev to virtual one if exist */
  

•   if (rk_iommu_is_virtual(iommu) || !rk_domain->dev)
  

Does it matter if the iommu is virtual or not? This condition will always evaluate to true on first attach anyway, so there might be times when rk_domain->dev points to a real device.

•           rk_domain->dev = iommu->dev;
  

[snip]

static void rk_iommu_detach_device(struct iommu_domain *domain, @@ -987,8 +1023,6 @@ static struct iommu_domain *rk_iommu_domain_alloc(unsigned type) if (!rk_domain->dt) goto err_dt;

•   rk_table_flush(rk_domain->dt, NUM_DT_ENTRIES);
  

•   spin_lock_init(&rk_domain->iommus_lock);
    spin_lock_init(&rk_domain->dt_lock);
    INIT_LIST_HEAD(&rk_domain->iommus);
  

@@ -1012,10 +1046,15 @@ static void rk_iommu_domain_free(struct iommu_domain *domain) if (rk_dte_is_pt_valid(dte)) { phys_addr_t pt_phys = rk_dte_pt_address(dte); u32 *page_table = phys_to_virt(pt_phys);

•                   dma_unmap_single(rk_domain->dev, pt_phys,
  

•                                    SPAGE_SIZE, DMA_TO_DEVICE);
                    free_page((unsigned long)page_table);
            }
    }
  
  

•   if (!rk_domain->dt_dma)
  

•           dma_unmap_single(rk_domain->dev, rk_domain->dt_dma,
  

•                            SPAGE_SIZE, DMA_TO_DEVICE);
    free_page((unsigned long)rk_domain->dt);
  
    iommu_put_dma_cookie(&rk_domain->domain);
  

If we detach here a device whose IOMMU is currently pointed by rk_domain->dev, then the pointer will not point to anything valid anymore. To be honest, I don't see any good solution for this. Maybe we should keep all the IOMMUs in a list and set the ->dev pointer to any from the list here?

Best regards, Tomasz