* [PATCH] drm/komeda: fix 32-bit komeda_crtc_update_clock_ratio
@ 2019-06-17 12:51 Arnd Bergmann
2019-06-17 13:33 ` Liviu Dudau
2019-06-18 2:05 ` james qian wang (Arm Technology China)
0 siblings, 2 replies; 3+ messages in thread
From: Arnd Bergmann @ 2019-06-17 12:51 UTC (permalink / raw)
To: James (Qian) Wang, Liviu Dudau, Brian Starkey, David Airlie,
Daniel Vetter
Cc: Arnd Bergmann, Lowry Li (Arm Technology China), dri-devel, linux-kernel
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 <arnd@arndb.de>
---
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] drm/komeda: fix 32-bit komeda_crtc_update_clock_ratio
2019-06-17 12:51 [PATCH] drm/komeda: fix 32-bit komeda_crtc_update_clock_ratio Arnd Bergmann
@ 2019-06-17 13:33 ` Liviu Dudau
2019-06-18 2:05 ` james qian wang (Arm Technology China)
1 sibling, 0 replies; 3+ messages in thread
From: Liviu Dudau @ 2019-06-17 13:33 UTC (permalink / raw)
To: Arnd Bergmann
Cc: James (Qian) Wang, Brian Starkey, David Airlie, Daniel Vetter,
Lowry Li (Arm Technology China),
dri-devel, linux-kernel
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 <arnd@arndb.de>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
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)_/¯
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] drm/komeda: fix 32-bit komeda_crtc_update_clock_ratio
2019-06-17 12:51 [PATCH] drm/komeda: fix 32-bit komeda_crtc_update_clock_ratio Arnd Bergmann
2019-06-17 13:33 ` Liviu Dudau
@ 2019-06-18 2:05 ` james qian wang (Arm Technology China)
1 sibling, 0 replies; 3+ messages in thread
From: james qian wang (Arm Technology China) @ 2019-06-18 2:05 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Liviu Dudau, Brian Starkey, David Airlie, Daniel Vetter,
Lowry Li (Arm Technology China),
dri-devel, linux-kernel, nd
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 <arnd@arndb.de>
> ---
> 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) <james.qian.wang@arm.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-06-17 12:51 [PATCH] drm/komeda: fix 32-bit komeda_crtc_update_clock_ratio Arnd Bergmann
2019-06-17 13:33 ` Liviu Dudau
2019-06-18 2:05 ` james qian wang (Arm Technology China)
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