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SubjectRe: [PATCH v2] drm: gem_cma_helper.c: Allow importing of contiguous scatterlists with nents > 1
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Den 15.11.2017 14.04, skrev Liviu Dudau:
> Hi,
>
> On Sat, Nov 11, 2017 at 02:47:35PM +0200, Laurent Pinchart wrote:
>> Hi Liviu,
>>
>> Thank you for the patch.
>>
>> On Friday, 10 November 2017 15:33:10 EET Liviu Dudau wrote:
>>> drm_gem_cma_prime_import_sg_table() will fail if the number of entries
>>> in the sg_table > 1. However, you can have a device that uses an IOMMU
>>> engine and can map a discontiguous buffer with multiple entries that
>>> have consecutive sg_dma_addresses, effectively making it contiguous.
>>> Allow for that scenario by testing the entries in the sg_table for
>>> contiguous coverage.
>>>
>>> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>>> Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
>>> ---
>>>
>>> Laurent,
>>>
>>> Thanks for the review! I would like to ask for one more favour: if you
>>> are OK with this version, can you pull this patch through the drm-misc tree?
>> I could, but I'd first need to set dim up, and I'm currently abroad with a bad
>> internet connection and a big deadline for the middle of next week (I know,
>> lots of excuses), so it's not very convenient for me at this time.
> Any other drm-misc maintainers feeling helpful and willing to take this
> patch in?

Sure, I can do it this evening.

Noralf.

> Otherwise I can send it through the mali-dp tree if no one
> objects.
>
> Best regards,
> Liviu
>
>>> drivers/gpu/drm/drm_gem_cma_helper.c | 22 ++++++++++++++++++++--
>>> include/drm/drm_gem_cma_helper.h | 4 +++-
>>> 2 files changed, 23 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c
>>> b/drivers/gpu/drm/drm_gem_cma_helper.c index 020e7668dfaba..43b179212052d
>>> 100644
>>> --- a/drivers/gpu/drm/drm_gem_cma_helper.c
>>> +++ b/drivers/gpu/drm/drm_gem_cma_helper.c
>>> @@ -482,8 +482,26 @@ drm_gem_cma_prime_import_sg_table(struct drm_device
>>> *dev, {
>>> struct drm_gem_cma_object *cma_obj;
>>>
>>> - if (sgt->nents != 1)
>>> - return ERR_PTR(-EINVAL);
>>> + if (sgt->nents != 1) {
>>> + /* check if the entries in the sg_table are contiguous */
>>> + dma_addr_t next_addr = sg_dma_address(sgt->sgl);
>>> + struct scatterlist *s;
>>> + unsigned int i;
>>> +
>>> + for_each_sg(sgt->sgl, s, sgt->nents, i) {
>>> + /*
>>> + * sg_dma_address(s) is only valid for entries
>>> + * that have sg_dma_len(s) != 0
>>> + */
>>> + if (!sg_dma_len(s))
>>> + continue;
>>> +
>>> + if (sg_dma_address(s) != next_addr)
>>> + return ERR_PTR(-EINVAL);
>>> +
>>> + next_addr = sg_dma_address(s) + sg_dma_len(s);
>>> + }
>>> + }
>>>
>>> /* Create a CMA GEM buffer. */
>>> cma_obj = __drm_gem_cma_create(dev, attach->dmabuf->size);
>>> diff --git a/include/drm/drm_gem_cma_helper.h
>>> b/include/drm/drm_gem_cma_helper.h index 58a739bf15f1f..214aa85adc8d5
>>> 100644
>>> --- a/include/drm/drm_gem_cma_helper.h
>>> +++ b/include/drm/drm_gem_cma_helper.h
>>> @@ -8,7 +8,9 @@
>>> * struct drm_gem_cma_object - GEM object backed by CMA memory allocations
>>> * @base: base GEM object
>>> * @paddr: physical address of the backing memory
>>> - * @sgt: scatter/gather table for imported PRIME buffers
>>> + * @sgt: scatter/gather table for imported PRIME buffers. The table can
>>> have + * more than one entry but they are guaranteed to have
>>> contiguous + * DMA addresses.
>>> * @vaddr: kernel virtual address of the backing memory
>>> */
>>> struct drm_gem_cma_object {
>> --
>> Regards,
>>
>> Laurent Pinchart
>>

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