[Intel-xe] [PATCH] drm/xe: Donot apply forcewake while reading actual frequency

[Nilawar, Badal]

Hi Matt,
On 08-06-2023 04:18, Matt Roper wrote:
> On Wed, Jun 07, 2023 at 01:40:04PM +0530, Badal Nilawar wrote:
>> The registers RPSTAT1, MTL_MIRROR_TARGET_WP1 doesn't fall under
>> any of the forcewake domain so doesn't require forcewake to be read.
>> When GT in RC6 frequency reported will be 0.
>>
>> Fixes: 7dbca224f176 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
>>
>> Signed-off-by: Badal Nilawar <badal.nilawar at intel.com>
> 
> RPSTAT1 is an sgunit register and thus doesn't need forcewake (which is
> a GT-only concept).  MTL_MIRROR_TARGET_WP1 is within an "always on"
> power domain and thus doesn't require any forcewake to ensure the
> register is powered up and usable.
Thanks for RB. I will incorporate above comment in commit message.
Regards,
Badal Nilawar
> 
> Reviewed-by: Matt Roper <matthew.d.roper at intel.com>
> 
>> ---
>>   drivers/gpu/drm/xe/xe_guc_pc.c | 10 +---------
>>   1 file changed, 1 insertion(+), 9 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_guc_pc.c b/drivers/gpu/drm/xe/xe_guc_pc.c
>> index 67faa9ee0006..d04600b943e4 100644
>> --- a/drivers/gpu/drm/xe/xe_guc_pc.c
>> +++ b/drivers/gpu/drm/xe/xe_guc_pc.c
>> @@ -371,14 +371,8 @@ static ssize_t freq_act_show(struct device *dev,
>>   	ssize_t ret;
>>   
>>   	xe_device_mem_access_get(gt_to_xe(gt));
>> -	/*
>> -	 * When in RC6, actual frequency is 0. Let's block RC6 so we are able
>> -	 * to verify that our freq requests are really happening.
>> -	 */
>> -	ret = xe_force_wake_get(gt_to_fw(gt), XE_FORCEWAKE_ALL);
>> -	if (ret)
>> -		goto out;
>>   
>> +	/* When in RC6, actual frequency reported will be 0. */
>>   	if (xe->info.platform == XE_METEORLAKE) {
>>   		freq = xe_mmio_read32(gt, MTL_MIRROR_TARGET_WP1);
>>   		freq = REG_FIELD_GET(MTL_CAGF_MASK, freq);
>> @@ -389,8 +383,6 @@ static ssize_t freq_act_show(struct device *dev,
>>   
>>   	ret = sysfs_emit(buf, "%d\n", decode_freq(freq));
>>   
>> -	XE_WARN_ON(xe_force_wake_put(gt_to_fw(gt), XE_FORCEWAKE_ALL));
>> -out:
>>   	xe_device_mem_access_put(gt_to_xe(gt));
>>   	return ret;
>>   }
>> -- 
>> 2.25.1
>>
>