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SubjectRe: [PATCH] drm: Fix for GEM buffers with write-combine memory
Hi Tomi,

Le ven., mai 28 2021 at 08:59:15 +0300, Tomi Valkeinen
<tomi.valkeinen@ideasonboard.com> a écrit :
> On 28/05/2021 02:03, Paul Cercueil wrote:
>> The previous commit wrongly assumed that dma_mmap_wc() could be
>> replaced
>> by pgprot_writecombine() + dma_mmap_pages(). It did work on my setup,
>> but did not work everywhere.
>>
>> Use dma_mmap_wc() when the buffer has the write-combine cache
>> attribute,
>> and dma_mmap_pages() when it has the non-coherent cache attribute.
>>
>> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>> Reported-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>> Fixes: cf8ccbc72d61 ("drm: Add support for GEM buffers backed by
>> non-coherent memory")
>> ---
>> drivers/gpu/drm/drm_gem_cma_helper.c | 16 ++++++++++------
>> 1 file changed, 10 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c
>> b/drivers/gpu/drm/drm_gem_cma_helper.c
>> index 235c7a63da2b..4c3772651954 100644
>> --- a/drivers/gpu/drm/drm_gem_cma_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_cma_helper.c
>> @@ -514,13 +514,17 @@ int drm_gem_cma_mmap(struct drm_gem_object
>> *obj, struct vm_area_struct *vma)
>>  cma_obj = to_drm_gem_cma_obj(obj);
>> - vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
>> - if (!cma_obj->map_noncoherent)
>> - vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
>> + if (cma_obj->map_noncoherent) {
>> + vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
>> +
>> + ret = dma_mmap_pages(cma_obj->base.dev->dev,
>> + vma, vma->vm_end - vma->vm_start,
>> + virt_to_page(cma_obj->vaddr));
>> + } else {
>> + ret = dma_mmap_wc(cma_obj->base.dev->dev, vma, cma_obj->vaddr,
>> + cma_obj->paddr, vma->vm_end - vma->vm_start);
>> - ret = dma_mmap_pages(cma_obj->base.dev->dev,
>> - vma, vma->vm_end - vma->vm_start,
>> - virt_to_page(cma_obj->vaddr));
>> + }
>> if (ret)
>> drm_gem_vm_close(vma);
>> 
>
> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>
> and
>
> Tested-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

Thanks, I applied it now.

>
> Thanks!
>
> Btw, the kernel-doc for drm_gem_cma_create doesn't quite match, as it
> says wc is always used.

Alright, I'll send a patch later for this one too.

Cheers,
-Paul


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