[PATCH 3/3] drm/amdgpu: Enable scatter gather display support

[Alex Deucher]

On Wed, Apr 18, 2018 at 5:51 PM, Samuel Li <Samuel.Li at amd.com> wrote:
> It's auto by default. For CZ/ST, auto setting enables sg display
> when vram size is small; otherwise still uses vram.
> This patch fixed some potention issues introduced by change
> "allow framebuffer in GART memory as well" due to CZ/ST hardware
> limitation.
>
> v2: Change default setting to auto.
> v3: Move some logic from amdgpu_display_framebuffer_domains()
>     to pin function, suggested by Christian.
> v4: Split into several patches.
>
> Signed-off-by: Samuel Li <Samuel.Li at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  2 ++
>  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c    |  4 ++++
>  drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 11 +++++++++++
>  3 files changed, 17 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index b3d047d..26429de 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -129,6 +129,7 @@ extern int amdgpu_lbpw;
>  extern int amdgpu_compute_multipipe;
>  extern int amdgpu_gpu_recovery;
>  extern int amdgpu_emu_mode;
> +extern int amdgpu_sg_display;
>
>  #ifdef CONFIG_DRM_AMDGPU_SI
>  extern int amdgpu_si_support;
> @@ -137,6 +138,7 @@ extern int amdgpu_si_support;
>  extern int amdgpu_cik_support;
>  #endif
>
> +#define AMDGPU_SG_THRESHOLD                    (256*1024*1024)
>  #define AMDGPU_DEFAULT_GTT_SIZE_MB             3072ULL /* 3GB by default */
>  #define AMDGPU_WAIT_IDLE_TIMEOUT_IN_MS         3000
>  #define AMDGPU_MAX_USEC_TIMEOUT                        100000  /* 100 ms */
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index 0b19482..85dcd1c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -132,6 +132,7 @@ int amdgpu_lbpw = -1;
>  int amdgpu_compute_multipipe = -1;
>  int amdgpu_gpu_recovery = -1; /* auto */
>  int amdgpu_emu_mode = 0;
> +int amdgpu_sg_display = -1;
>
>  MODULE_PARM_DESC(vramlimit, "Restrict VRAM for testing, in megabytes");
>  module_param_named(vramlimit, amdgpu_vram_limit, int, 0600);
> @@ -290,6 +291,9 @@ module_param_named(gpu_recovery, amdgpu_gpu_recovery, int, 0444);
>  MODULE_PARM_DESC(emu_mode, "Emulation mode, (1 = enable, 0 = disable)");
>  module_param_named(emu_mode, amdgpu_emu_mode, int, 0444);
>
> +MODULE_PARM_DESC(sg_display, "Enable scatter gather display, (1 = enable, 0 = disable, -1 = auto");
> +module_param_named(sg_display, amdgpu_sg_display, int, 0444);
> +
>  #ifdef CONFIG_DRM_AMDGPU_SI
>
>  #if defined(CONFIG_DRM_RADEON) || defined(CONFIG_DRM_RADEON_MODULE)
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> index 8dc782a..cb0807c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> @@ -696,6 +696,17 @@ int amdgpu_bo_pin_restricted(struct amdgpu_bo *bo, u32 domain,
>                         return -EINVAL;
>         }
>
> +       /* This assumes only apu display buffers pin with (VRAM|GTT) */
> +       if (domain == (AMDGPU_GEM_DOMAIN_VRAM | AMDGPU_GEM_DOMAIN_GTT)) {
> +               domain = AMDGPU_GEM_DOMAIN_VRAM;
> +               if (amdgpu_sg_display == 1)
> +                       domain = AMDGPU_GEM_DOMAIN_GTT;
> +               else if (amdgpu_sg_display == -1) {
> +                       if (adev->gmc.real_vram_size <= AMDGPU_SG_THRESHOLD)
> +                               domain = AMDGPU_GEM_DOMAIN_GTT;
> +               }
> +       }

Please drop the module parameter.  I can't see any reason for it.  We
are ending up with too many driver parameters of questionable value.
If the user would prefer GTT over VRAM or vice versa, we should take
those preferences (from the UMDs) into account at pinning time as I
said earlier rather than globally at as a driver option.  E.g.,

if (bo->preferred_domains == AMDGPU_GEM_DOMAIN_VRAM)
    domain = AMDGPU_GEM_DOMAIN_VRAM; /* if user really wants vram, respect it */
else if (bo->preferred_domains == AMDGPU_GEM_DOMAIN_GTT)
    domain = AMDGPU_GEM_DOMAIN_GTT; /* if user really wants gtt, respect it */
else if (adev->gmc.real_vram_size <= AMDGPU_SG_THRESHOLD)
    domain = AMDGPU_GEM_DOMAIN_GTT; /* if vram is limited, use gtt */
else
    domain = AMDGPU_GEM_DOMAIN_VRAM;

Alex

> +
>         if (bo->pin_count) {
>                 uint32_t mem_type = bo->tbo.mem.mem_type;
>
> --
> 2.7.4
>
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