[PATCH] drm/xe: Initialize freq_lock even with skip_guc_pc

[Belgaumkar, Vinay]

On 1/12/2024 1:10 PM, Rodrigo Vivi wrote:
> On Fri, Jan 12, 2024 at 10:29:50AM -0800, Matt Roper wrote:
>> gucpc isn't initialized when skip_guc_pc is used, but some of the sysfs
>> frequency entries still try to grab the uninitialized frequency mutex
>> before realizing that they need to bail out.  Tweak the init/fini code
>> flows so that the mutex is always initialized properly.
> hmmm... good catch.
> But I honestly don't believe we should be calling/running any function
> that is trying to get the freq_lock. If guc pc is skip, why would we try
> to communicate with guc to get or set the freq?
>
> The shared buffers are not set and all. We need a deeper decoupling here.
> Vinay?

Yeah, the frequency related sysfs are definitely not being created when 
skip_guc_pc is set. @Matt, do we know which sysfs entries are causing this?

Thanks,

Vinay.

>
>> Fixes: 975e4a3795d4 ("drm/xe: Manually setup C6 when skip_guc_pc is set")
>> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
>> Cc: Vinay Belgaumkar <vinay.belgaumkar at intel.com>
>> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_guc_pc.c | 9 +++++----
>>   1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_guc_pc.c b/drivers/gpu/drm/xe/xe_guc_pc.c
>> index f71085228cb3..67ce24fae79d 100644
>> --- a/drivers/gpu/drm/xe/xe_guc_pc.c
>> +++ b/drivers/gpu/drm/xe/xe_guc_pc.c
>> @@ -964,11 +964,12 @@ void xe_guc_pc_fini(struct xe_guc_pc *pc)
>>   
>>   	if (xe->info.skip_guc_pc) {
>>   		xe_gt_idle_disable_c6(pc_to_gt(pc));
>> -		return;
>> +		goto out;
>>   	}
>>   
>>   	XE_WARN_ON(xe_guc_pc_gucrc_disable(pc));
>>   	XE_WARN_ON(xe_guc_pc_stop(pc));
>> +out:
>>   	mutex_destroy(&pc->freq_lock);
>>   }
>>   
>> @@ -984,11 +985,11 @@ int xe_guc_pc_init(struct xe_guc_pc *pc)
>>   	struct xe_bo *bo;
>>   	u32 size = PAGE_ALIGN(sizeof(struct slpc_shared_data));
>>   
>> -	if (xe->info.skip_guc_pc)
>> -		return 0;
>> -
>>   	mutex_init(&pc->freq_lock);
>>   
>> +	if (xe->info.skip_guc_pc)
>> +		return 0;
>> +
>>   	bo = xe_managed_bo_create_pin_map(xe, tile, size,
>>   					  XE_BO_CREATE_VRAM_IF_DGFX(tile) |
>>   					  XE_BO_CREATE_GGTT_BIT);
>> -- 
>> 2.43.0
>>