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

[Alex Deucher]

On Sat, Feb 3, 2018 at 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 
> Cc: Alex Deucher 
> Cc: Harry Wentland 
> Signed-off-by: Dhinakaran Pandiyan 

Acked-by: Alex Deucher  for both this patch
and the radeon one.

> ---
>  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);
> }
>
> --
> 2.14.1
>
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Re: [Intel-gfx] [PATCH 04/10] drm/amdgpu: Handle 64-bit return from drm_crtc_vblank_count()

[Harry Wentland]

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 
> Cc: Alex Deucher 
> Cc: Harry Wentland 
> Signed-off-by: Dhinakaran Pandiyan 

Reviewed-by: Harry Wentland 

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

[Dhinakaran Pandiyan]

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 
Cc: Alex Deucher 
Cc: Harry Wentland 
Signed-off-by: Dhinakaran Pandiyan 
---
 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);
}
 
-- 
2.14.1

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