[PATCH] drm: exynos: fix for mapping non contig dma buffers

[Rahul Sharma]

Thanks Mr. Dae,

I improvised the above patch and submitted another patch for contiguous buffer.

regards,
Rahul Sharma

On Fri, Nov 2, 2012 at 10:14 AM, Inki Dae <inki.dae at samsung.com> wrote:
> It's good patch. Right, there was my missing point. I thought each sgl would
> always have 4k page. But dma mapping api, dma_alloc_alloc(), allocates
> physical memory as continuously as possible so the sgl can have group of
> pages.
>
> Below is my comment.
>
>
>> -----Original Message-----
>> From: Rahul Sharma [mailto:rahul.sharma at samsung.com]
>> Sent: Thursday, November 01, 2012 9:35 PM
>> To: dri-devel at lists.freedesktop.org
>> Cc: sw0312.kim at samsung.com; inki.dae at samsung.com; jy0922.shim at samsung.com;
>> kyungmin.park at samsung.com; prashanth.g at samsung.com; joshi at samsung.com;
>> s.shirish at samsung.com; r.sh.open at gmail.com; rahul.sharma at samsung.com
>> Subject: [PATCH] drm: exynos: fix for mapping non contig dma buffers
>>
>> This patch fixes the problem of mapping gem objects which are non-
>> contigous
>> dma buffers. These buffers are described using SG table and SG lists. Each
>> valid SG List is pointing to a single page or group of pages which are
>> physically contigous.
>>
>> Current implementation just maps the first page of each SG List and leave
>> the other pages unmapped, leading to a crash.
>>
>> Given solution finds the page struct for all the pages in the SG list and
>> map them one by one. This ensures all the pages of current SG list are
>> mapped.
>> Next SG list of the same buffer will be mapped when page fault occurs for
>> the offset belongs to that list.
>>
>> This patch is based on branch exynos-drm-next-iommu at
>> git://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos.git
>>
>> Signed-off-by: Rahul Sharma <rahul.sharma at samsung.com>
>> ---
>>  drivers/gpu/drm/exynos/exynos_drm_gem.c |   34
>> +++++++++++++++++++++++++++---
>>  1 files changed, 30 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/exynos/exynos_drm_gem.c
>> b/drivers/gpu/drm/exynos/exynos_drm_gem.c
>> index 7057729..d2d6188 100644
>> --- a/drivers/gpu/drm/exynos/exynos_drm_gem.c
>> +++ b/drivers/gpu/drm/exynos/exynos_drm_gem.c
>> @@ -95,17 +95,43 @@ static int exynos_drm_gem_map_buf(struct
>> drm_gem_object *obj,
>>  {
>>       struct exynos_drm_gem_obj *exynos_gem_obj = to_exynos_gem_obj(obj);
>>       struct exynos_drm_gem_buf *buf = exynos_gem_obj->buffer;
>> +     struct scatterlist *sgl;
>>       unsigned long pfn;
>> +     unsigned int phys_addr;
>> +     int ret, i;
>>
>>       if (exynos_gem_obj->flags & EXYNOS_BO_NONCONTIG) {
>>               if (!buf->pages)
>>                       return -EINTR;
>
> Buf->pages should be checked in all cases. For this, see below comment.
>
>>
>> -             pfn = page_to_pfn(buf->pages[page_offset++]);
>> -     } else
>> +             sgl = buf->sgt->sgl;
>> +             for_each_sg(buf->sgt->sgl, sgl, buf->sgt->nents, i) {
>> +                     if (page_offset < (sgl->length >> PAGE_SHIFT))
>> +                             break;
>> +                     page_offset -=  (sgl->length >> PAGE_SHIFT);
>> +             }
>> +
>> +             if (i >= buf->sgt->nents) {
>> +                     DRM_ERROR("invalid page offset\n");
>> +                     return -EINVAL;
>> +             }
>> +
>> +             phys_addr = sg_phys(sgl);
>> +
>> +             for (i = 0; i < (sgl->length >> PAGE_SHIFT); i++) {
>> +                     pfn = __phys_to_pfn(phys_addr + (i << PAGE_SHIFT));
>> +                     ret = vm_insert_mixed(vma, f_vaddr + (i <<
> PAGE_SHIFT),
>> +                                             pfn);
>> +                     if (ret < 0) {
>> +                             DRM_ERROR("failed to map page.\n");
>> +                             return ret;
>> +                     }
>> +             }
>> +             return 0;
>> +     } else {
>>               pfn = (buf->dma_addr >> PAGE_SHIFT) + page_offset;
>
> It seems like that you missed EXYNOS_BO_CONTIG type testing. With iommu,
> buf->dma_addr has device address but not physical address. So correct it
> like below,
>         pfn = page_to_pfn(buf->pages[0]) + page_offset;
>
> And one more posting? :)
>
> Thanks,
> Inki Dae
>
>> -
>> -     return vm_insert_mixed(vma, f_vaddr, pfn);
>> +             return vm_insert_mixed(vma, f_vaddr, pfn);
>> +     }
>>  }
>>
>>  static int exynos_drm_gem_handle_create(struct drm_gem_object *obj,
>> --
>> 1.7.0.4
>