Re: [PATCH 04/10] drm/amdgpu: Handle 64-bit return from drm_crtc_vblank_count()

Harry Wentland
2018-02-05T15:20:09Z

On 2018-02-03 12:12 AM, Dhinakaran Pandiyan wrote:
> 570e86963a51 ("drm: Widen vblank count to 64-bits [v3]") changed the
> return type for drm_crtc_vblank_count() to u64. This could cause
> potential problems if the return value is used in arithmetic operations
> with a 32-bit reference HW vblank count. Explicitly typecasting this down
> to u32 either fixes a potential problem or serves to add clarity in case
> the typecasting was implicitly done.
>
> Cc: Keith Packard <keithp@keithp.com>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>

Reviewed-by: Harry Wentland <harry.wentland@amd.com>

Harry

> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_display.c | 2 +-
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> index 38d47559f098..c2fa5d55f04e 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> @@ -207,7 +207,7 @@ int amdgpu_crtc_page_flip_target(struct drm_crtc *crtc,
> amdgpu_bo_unreserve(new_abo);
>
> work->base = base;
> - work->target_vblank = target - drm_crtc_vblank_count(crtc) +
> + work->target_vblank = target - (uint32_t)drm_crtc_vblank_count(crtc) +
> amdgpu_get_vblank_counter_kms(dev, work->crtc_id);
>
> /* we borrow the event spin lock for protecting flip_wrok */
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 1ce4c98385e3..b7254a29b34a 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -3836,7 +3836,7 @@ static void amdgpu_dm_do_flip(struct drm_crtc *crtc,
>
>
> /* Prepare wait for target vblank early - before the fence-waits */
> - target_vblank = target - drm_crtc_vblank_count(crtc) +
> + target_vblank = target - (uint32_t)drm_crtc_vblank_count(crtc) +
> amdgpu_get_vblank_counter_kms(crtc->dev, acrtc->crtc_id);
>
> /* TODO This might fail and hence better not used, wait
> @@ -3982,7 +3982,7 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
> amdgpu_dm_do_flip(
> crtc,
> fb,
> - drm_crtc_vblank_count(crtc) + *wait_for_vblank,
> + (uint32_t)drm_crtc_vblank_count(crtc) + *wait_for_vblank,
> dm_state->context);
> }
>
>
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