[PATCH] drm/amdgpu: Fix incorrect return value in sysfs for pp_od_clk_voltage

[Deucher, Alexander]

[AMD Public Use]

No need to apologize, it was a good catch.  Something to double check in the future if something similar ends up getting applied again.

Thanks!

Alex
________________________________
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Matt Coffin <mcoffin13 at gmail.com>
Sent: Friday, August 14, 2020 3:13 PM
To: amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
Cc: Quan, Evan <Evan.Quan at amd.com>; Koenig, Christian <Christian.Koenig at amd.com>; Li, Dennis <Dennis.Li at amd.com>
Subject: Re: [PATCH] drm/amdgpu: Fix incorrect return value in sysfs for pp_od_clk_voltage

Hi all,

As of 026acaeac2d205f22c0f682cc1c7b1a85b9ccd00 ("drm/amdgpu: revert "fix
system hang issue during GPU reset""), this patch is no longer needed,
and won't apply, because the badly-behaving code was removed; I'll
withdraw this patch for now.

Sorry to those who wasted their time reviewing.

Cheers,
Matt

On 8/13/20 7:15 PM, Matt Coffin wrote:
> The changes in edad8312cbbf9a33c86873fc4093664f150dd5c1 introduced an
> issue with the sysfs interface for pp_od_clk_voltage. It overwrites the
> return value to 0 when it calls another function, then returns 0. The
> intended behavior is that a positive return value indicates the number
> of bytes from the buffer that you processed in that call.
>
> With the 0 return value, clients would submit the same value to be
> written over and over again, resulting in an infinite loop.
>
> This is resolved by returning the count of bytes read (in this case the
> whole message), when the desired return is 0 (success).
>
> Fixes: edad8312cbbf ("drm/amdgpu: fix system hang issue during GPU")
> Bug: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Fdrm%2Famd%2F-%2Fissues%2F1245&data=02%7C01%7Calexander.deucher%40amd.com%7C3fb1fd9f95ad441a88a208d840862e80%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637330292979204288&sdata=iABLxfzQVQa5zBK6a0JozvRYl%2Fg5eTFnfOS86r0g9rU%3D&reserved=0
> Signed-off-by: Matt Coffin <mcoffin13 at gmail.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
> index 1705e328c6fc..f00c7ed361d4 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
> @@ -937,7 +937,11 @@ static ssize_t amdgpu_set_pp_od_clk_voltage(struct device *dev,
>
>  pro_end:
>        up_read(&adev->reset_sem);
> -     return ret;
> +     if (ret) {
> +             return ret;
> +     } else {
> +             return count;
> +     }
>  }
>
>  static ssize_t amdgpu_get_pp_od_clk_voltage(struct device *dev,
>
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