Re: [PATCH] drm/komeda: fix 32-bit komeda_crtc_update_clock_ratio

2019-06-17 Thread james qian wang (Arm Technology China) 
On Mon, Jun 17, 2019 at 02:51:04PM +0200, Arnd Bergmann wrote:
> clang points out a bug in the clock calculation on 32-bit, that leads
> to the clock_ratio always being zero:
> 
> drivers/gpu/drm/arm/display/komeda/komeda_crtc.c:31:36: error: shift count >= 
> width of type [-Werror,-Wshift-count-overflow]
> aclk = komeda_calc_aclk(kcrtc_st) << 32;
> 
> Move the shift into the division to make it apply on a 64-bit
> variable. Also use the more expensive div64_u64() instead of div_u64()
> to account for pxlclk being a 64-bit integer.
> 
> Fixes: a962091227ed ("drm/komeda: Add engine clock requirement check for the 
> downscaling")
> Signed-off-by: Arnd Bergmann 
> ---
>  drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c 
> b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> index cafb4457e187..3f222f464eb2 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> @@ -28,10 +28,9 @@ static void komeda_crtc_update_clock_ratio(struct 
> komeda_crtc_state *kcrtc_st)
>   }
>  
>   pxlclk = kcrtc_st->base.adjusted_mode.clock * 1000;
> - aclk = komeda_calc_aclk(kcrtc_st) << 32;
> + aclk = komeda_calc_aclk(kcrtc_st);
>  
> - do_div(aclk, pxlclk);
> - kcrtc_st->clock_ratio = aclk;
> + kcrtc_st->clock_ratio = div64_u64(aclk << 32, pxlclk);
>  }
>  
>  /**
> -- 
> 2.20.0

Hi Arnd:

Thank you for the patch.

Reviewed-by: James Qian Wang (Arm Technology China) 
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Re: [PATCH] drm/komeda: fix 32-bit komeda_crtc_update_clock_ratio

2019-06-17 Thread Liviu Dudau 
On Mon, Jun 17, 2019 at 02:51:04PM +0200, Arnd Bergmann wrote:
> clang points out a bug in the clock calculation on 32-bit, that leads
> to the clock_ratio always being zero:
> 
> drivers/gpu/drm/arm/display/komeda/komeda_crtc.c:31:36: error: shift count >= 
> width of type [-Werror,-Wshift-count-overflow]
> aclk = komeda_calc_aclk(kcrtc_st) << 32;
> 
> Move the shift into the division to make it apply on a 64-bit
> variable. Also use the more expensive div64_u64() instead of div_u64()
> to account for pxlclk being a 64-bit integer.
> 
> Fixes: a962091227ed ("drm/komeda: Add engine clock requirement check for the 
> downscaling")
> Signed-off-by: Arnd Bergmann 

Acked-by: Liviu Dudau 

Thanks for the patch, I will pull it into the komeda tree.

Best regards,
Liviu

> ---
>  drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c 
> b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> index cafb4457e187..3f222f464eb2 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> @@ -28,10 +28,9 @@ static void komeda_crtc_update_clock_ratio(struct 
> komeda_crtc_state *kcrtc_st)
>   }
>  
>   pxlclk = kcrtc_st->base.adjusted_mode.clock * 1000;
> - aclk = komeda_calc_aclk(kcrtc_st) << 32;
> + aclk = komeda_calc_aclk(kcrtc_st);
>  
> - do_div(aclk, pxlclk);
> - kcrtc_st->clock_ratio = aclk;
> + kcrtc_st->clock_ratio = div64_u64(aclk << 32, pxlclk);
>  }
>  
>  /**
> -- 
> 2.20.0
> 

-- 

| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---
¯\_(ツ)_/¯
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[PATCH] drm/komeda: fix 32-bit komeda_crtc_update_clock_ratio

2019-06-17 Thread Arnd Bergmann 
clang points out a bug in the clock calculation on 32-bit, that leads
to the clock_ratio always being zero:

drivers/gpu/drm/arm/display/komeda/komeda_crtc.c:31:36: error: shift count >= 
width of type [-Werror,-Wshift-count-overflow]
aclk = komeda_calc_aclk(kcrtc_st) << 32;

Move the shift into the division to make it apply on a 64-bit
variable. Also use the more expensive div64_u64() instead of div_u64()
to account for pxlclk being a 64-bit integer.

Fixes: a962091227ed ("drm/komeda: Add engine clock requirement check for the 
downscaling")
Signed-off-by: Arnd Bergmann 
---
 drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c 
b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
index cafb4457e187..3f222f464eb2 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
@@ -28,10 +28,9 @@ static void komeda_crtc_update_clock_ratio(struct 
komeda_crtc_state *kcrtc_st)
}
 
pxlclk = kcrtc_st->base.adjusted_mode.clock * 1000;
-   aclk = komeda_calc_aclk(kcrtc_st) << 32;
+   aclk = komeda_calc_aclk(kcrtc_st);
 
-   do_div(aclk, pxlclk);
-   kcrtc_st->clock_ratio = aclk;
+   kcrtc_st->clock_ratio = div64_u64(aclk << 32, pxlclk);
 }
 
 /**
-- 
2.20.0

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