On Thu, Jan 31, 2013 at 2:23 PM, Daniel Vetter daniel@ffwll.ch wrote:
On Thu, Jan 31, 2013 at 9:38 AM, Rahul Sharma r.sh.open@gmail.com wrote:
On Tue, Jan 29, 2013 at 10:40 PM, Aaron Plattner aplattner@nvidia.com wrote:
On 01/28/2013 05:38 AM, Rahul Sharma wrote:
It fixes the issue arises due to passing 'nr_pages' in place of 'nents' to sg_alloc_table. When ARM_HAS_SG_CHAIN is disabled, it is causing failure in creating SG table for the buffers having more than 204 physical pages i.e. equal to SG_MAX_SINGLE_ALLOC.
When using sg_alloc_table_from_pages interface, in place of sg_alloc_table, page list will be passes to get each contiguous section which is represented by a single entry in the table. For a Contiguous Buffer, number of entries should be equal to 1.
Following check is causing the failure which is not applicable for Non-Contig buffers:
if (WARN_ON_ONCE(nents > max_ents)) return -EINVAL;Above patch is well tested for EXYNOS4 and EXYNOS5 for with/wihtout IOMMU supprot. NOUVEAU and RADEON platforms also depends on drm_prime_pages_to_sg helper function.
This set is base on "exynos-drm-fixes" branch at http://git.kernel.org/?p=linux/kernel/git/daeinki/drm-exynos.git
Signed-off-by: Rahul Sharma rahul.sharma@samsung.com
Reviewed-by: Aaron Plattner aplattner@nvidia.com
I also verified that this reduces my 2025-entry sg_table to 6 entries, so
Tested-by: Aaron Plattner aplattner@nvidia.com
-- Aaron
Thanks Aaron,
I want to request stake-holders to review and test this patch for other platforms.
Iirc the old i915 dma_buf import code presumed that each sg entry points to exactly one page. Yeah, Dave cut a few corners in the initial implementation. Since Chris' rework to use sg_tables internally in i915.ko I think we should be safe, but would need to do a full audit of the code. No idea what the exact situation in ttm is.
So I think step one is for you to crawl through the existing drm prime drivers and check that you don't break any hidden assumptions about this.
Thanks Daniel,
I have parsed the related code and it looks fine to me. I couldn't find any code section, expecting sg-tables with single-page sgl entries. I just want to ensure again that it doesn't cause any side effects on various platforms.
For the patch itself I think there's now a generic pages_to_sg helper in the dma core which does exactly what you want it to do. I can dig it out if you can't find it.
Sorry, I din't get this part. Please elaborate a bit.
regards, Rahul Sharma.
Cheers, Daniel
Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch