[PATCH 2/2] drm/xe: Fix xe_force_wake_assert_held for enum XE_FORCEWAKE_ALL

[Ghimiray, Himal Prasad]

On 31-05-2024 18:49, Rodrigo Vivi wrote:
> On Fri, May 31, 2024 at 12:18:45PM +0530, Himal Prasad Ghimiray wrote:
>> Make sure that the assertion condition covers the wakefulness of all
>> supported domains for XE_FORCEWAKE_ALL.
> The most important part is missing here: why? what issue are we trying to solve?

Hi Rodrigo,

AFAIU,  xe_force_wake_assert_held is designed to trigger an assertion if 
the provided domain is not awake, which works correctly for individual 
domains. However, the assertion condition becomes incorrect for 
XE_FORCEWAKE_ALL.

For instance, if we assume all domains are in sleep mode, invoking 
|xe_force_wake_get(fw, XE_FORCEWAKE_GT)| will only awaken the "gt" 
domain. Subsequently, another function needs that all domains are awake 
and utilizes |xe_force_wake_assert_held(fw, XE_FORCEWAKE_ALL)|.

In this scenario, the condition will inaccurately return success because 
|fw->awake_domains| (0x1) & |XE_FORCEWAKE_ALL| (0xFF) will still be 0x1 
and Ideally it should have asserted.

>
>> Cc: Rodrigo Vivi<rodrigo.vivi at intel.com>
>> Cc: Badal Nilawar<badal.nilawar at intel.com>
>> Signed-off-by: Himal Prasad Ghimiray<himal.prasad.ghimiray at intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_force_wake.h | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_force_wake.h b/drivers/gpu/drm/xe/xe_force_wake.h
>> index 83cb157da7cc..4c986d72cba7 100644
>> --- a/drivers/gpu/drm/xe/xe_force_wake.h
>> +++ b/drivers/gpu/drm/xe/xe_force_wake.h
>> @@ -32,7 +32,12 @@ static inline void
>>   xe_force_wake_assert_held(struct xe_force_wake *fw,
>>   			  enum xe_force_wake_domains domain)
>>   {
>> -	xe_gt_assert(fw->gt, fw->awake_domains & domain);
>> +	enum xe_force_wake_domains is_awake;
>> +
>> +	is_awake = (domain == XE_FORCEWAKE_ALL) ?
>> +		    fw->supported_domains : domain;
>> +
>> +	xe_gt_assert(fw->gt, (fw->awake_domains & is_awake) == is_awake);
>>   }
>>   
>>   #endif
>> -- 
>> 2.25.1
>>
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