[PATCH] drm/amd/amdgpu: Fix wave mask in amdgpu_debugfs_wave_read()

[Tom St Denis]

On 12/11/17 03:57 AM, Christian König wrote:
> Am 10.11.2017 um 19:29 schrieb Tom St Denis:
>> On 10/11/17 01:20 PM, Christian König wrote:
>>> Am 10.11.2017 um 19:03 schrieb Tom St Denis:
>>>> The bottom two bits of the simd value were being put into
>>>> the upper bits of the wave value which was likely working due
>>>> to the bits being ignored (or aliased).
>>>>
>>>> Eitherway, now we mask it correctly.
>>>>
>>>> Signed-off-by: Tom St Denis <tom.stdenis at amd.com>
>>>> ---
>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c 
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> index c1f1b8f15395..cc59020d5874 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> @@ -3766,7 +3766,7 @@ static ssize_t amdgpu_debugfs_wave_read(struct 
>>>> file *f, char __user *buf,
>>>>       se = ((*pos >> 7) & 0xFF);
>>>>       sh = ((*pos >> 15) & 0xFF);
>>>>       cu = ((*pos >> 23) & 0xFF);
>>>> -    wave = ((*pos >> 31) & 0xFF);
>>>> +    wave = ((*pos >> 31) & 0x3F);
>>>>       simd = ((*pos >> 37) & 0xFF);
>>>
>>> Have you considered using GENMASK_ULL instead of fiddling with the 
>>> hex masks manually?
>>>
>>> E.g. that would look like this
>>>
>>> se = (*pos & GENMASK_ULL(14, 7)) >> 7;
>>> sh = (*pos & GENMASK_ULL(22, 15)) >> 15;
>>> cu = (*pos & GENMASK_ULL(30, 23)) >> 23;
>>> wave = (*pos & GENMASK_ULL(36, 31)) >> 31;
>>> simd = (*pos & GENMASK_ULL(44, 37)) >> 37;
>>>
>>> if you ask me makes it totally obvious what is happening here and 
>>> avoids such typos.
>>>
>>> Might be that we even have some GENMASK_ULL + shift macro somewhere 
>>> in the kernel, but I don't know of anything of hand.
>>>
>>> Christian.
>>
>>
>> I'll take a gander it's a good suggestion.  Though this could apply to 
>> 3 other functions in the debugfs side.  Maybe do a fix patch first and 
>> then another patch to switch all 4 functions over to a cleaner 
>> approach (using GENMASK_ULL/etc)?
> 
> For kernel work I would usually prefer a patch which fixes the original 
> issue and then another one to clean up the coding and move to 
> GENMASK_ULL, but it is such a minor issue that I probably don't care much.

Hi Christian,

Cool because I had sent a v2 to the list on Friday later in the day :-). 
  Could use an R-b.

Cheers,
Tom