[PATCH] drm/exynos: fix gem buffer allocation type checking

[Inki Dae]

2012/12/27 Prathyush K <prathyush at chromium.org>

>
>
>
> On Thu, Dec 27, 2012 at 4:27 PM, Inki Dae <inki.dae at samsung.com> wrote:
>
>> This patch fixes gem buffer allocation type checking.
>> EXYNOS_BO_CONTIG has 0 so the checking should be fixed
>> to 'if (!(flags & EXYNOS_BO_NONCONTIG))'
>>
>> Signed-off-by: Inki Dae <inki.dae at samsung.com>
>> Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
>> ---
>>  drivers/gpu/drm/exynos/exynos_drm_buf.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/exynos/exynos_drm_buf.c
>> b/drivers/gpu/drm/exynos/exynos_drm_buf.c
>> index 74592d1..911f7fd 100644
>> --- a/drivers/gpu/drm/exynos/exynos_drm_buf.c
>> +++ b/drivers/gpu/drm/exynos/exynos_drm_buf.c
>> @@ -38,7 +38,7 @@ static int lowlevel_buffer_allocate(struct drm_device
>> *dev,
>>          * region will be allocated else physically contiguous
>>          * as possible.
>>          */
>> -       if (flags & EXYNOS_BO_CONTIG)
>> +       if (!(flags & EXYNOS_BO_NONCONTIG))
>>                 dma_set_attr(DMA_ATTR_FORCE_CONTIGUOUS, &buf->dma_attrs);
>>
>>
> Hi Mr. Dae,
>
> If iommu is supported, we would have called arm_iommu_attach_device.
> So dma_alloc_attrs will always call arm_iommu_alloc_attrs.
>
> If iommu is not supported, dma_alloc_attrs will call arm_dma_alloc which
> will
> anyway allocate a contiguous buffer if possible.
>
> With this code, we are forcing the root framebuffer (fbdev) to be
> contiguous since fbdev
> allocation does not pass noncontig flag.
>
>
we could use noncontig flag simply like below,

          if (iommu is supported)
                  exynos_drm_gem_create(dev, EXYNOS_BO_NONCONTIG, size);
          else
                  exynos_drm_gem_create(dev, EXYNOS_BO_CONTIG, size);



> Why do we need to force the allocation of a contiguous buffer when iommu
> is supported?
>
>
Simply saying, the reason is that we want to pass boot logo drew by boot
loader without iommu to kernel side without memory copy.


> Regards,
> Prathyush
>
>
>>         /*
>> --
>> 1.7.4.1
>>
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