Re: [PATCH] drm: powerplay: use div64_s64 instead of do_div

[Christian KÃnig]

On 01.01.2016 14:07, Arnd Bergmann wrote:
> The newly added code for Fiji creates a correct compiler warning
> about invalid use of the do_div macro:
>
> In file included from powerplay/hwmgr/ppatomctrl.c:31:0:
> drivers/gpu/drm/amd/amdgpu/../powerplay/hwmgr/ppevvmath.h: In function 'fDivide':
> drivers/gpu/drm/amd/amdgpu/../powerplay/hwmgr/ppevvmath.h:382:89: warning: comparison of distinct pointer types lacks a cast
>       do_div(longlongX, longlongY); /*Q(32,32) divided by Q(16,16) = Q(16,16) Back to original format */
>
> do_div() divides an unsigned 64-bit number by an unsigned 32-bit number.
> The code instead wants to divide two signed 64-bit numbers, which is done
> using the div64_s64 function.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

Reviewed-by: Christian König <christian.koenig@xxxxxxx>

> Fixes: 770911a3cfbb ("drm/amd/powerplay: add/update headers for Fiji SMU and DPM")
> ---
> Found on ARM allmodconfig on yesterday's linux-next
>
> diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/ppevvmath.h b/drivers/gpu/drm/amd/powerplay/hwmgr/ppevvmath.h
> index 42f2423cddea..411cb0fcdf98 100644
> --- a/drivers/gpu/drm/amd/powerplay/hwmgr/ppevvmath.h
> +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/ppevvmath.h
> @@ -379,7 +379,7 @@ fInt fDivide (fInt X, fInt Y)
>   
>       longlongX = longlongX << 16; /*Q(16,16) -> Q(32,32) */
>   
> -    do_div(longlongX, longlongY); /*Q(32,32) divided by Q(16,16) = Q(16,16) Back to original format */
> +    div64_s64(longlongX, longlongY); /*Q(32,32) divided by Q(16,16) = Q(16,16) Back to original format */
>   
>       fQuotient.full = (int)longlongX;
>       return fQuotient;

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