linux-kernel - Re: [PATCH 02/11 V2] radeon: evergreen: Fix probable mask then right shift defect

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Date:	Tue, 28 Oct 2014 12:42:05 +0900
From:	Michel Dänzer <michel@...nzer.net>
To:	Joe Perches <joe@...ches.com>
CC:	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/11 V2] radeon: evergreen: Fix probable mask
 then right shift defect

On 27.10.2014 23:14, Joe Perches wrote:
> Precedence of & and >> is not the same and is not left to right.
> shift has higher precedence and should be done after the mask.
>
> Add parentheses around the mask.
>
> Use the already #defined values instead of hardcoding.
>
> Signed-off-by: Joe Perches <joe@...ches.com>
> ---
>> I think this should be NUM_SHADER_ENGINES_SHIFT?
>
> (Joe can't type)
>
> exactly right, thanks Michel
>
>   drivers/gpu/drm/radeon/evergreen.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
> index a31f1ca..a97a685 100644
> --- a/drivers/gpu/drm/radeon/evergreen.c
> +++ b/drivers/gpu/drm/radeon/evergreen.c
> @@ -3303,7 +3303,8 @@ static void evergreen_gpu_init(struct radeon_device *rdev)
>   	rdev->config.evergreen.tile_config |=
>   		((gb_addr_config & 0x30000000) >> 28) << 12;
>
> -	num_shader_engines = (gb_addr_config & NUM_SHADER_ENGINES(3) >> 12) + 1;
> +	num_shader_engines = ((gb_addr_config & NUM_SHADER_ENGINES_MASK)
> +			      >> NUM_SHADER_ENGINES_SHIFT) + 1;
>
>   	if ((rdev->family >= CHIP_CEDAR) && (rdev->family <= CHIP_HEMLOCK)) {
>   		u32 efuse_straps_4;

Reviewed-by: Michel Dänzer <michel.daenzer@....com>


-- 
Earthling Michel Dänzer            |                  http://www.amd.com
Libre software enthusiast          |                Mesa and X developer
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