[PATCH v6 3/4] drm/i915: Reset steer semaphore for media GT on resume

[Nirmoy Das]

On 9/28/2023 12:35 AM, Matt Roper wrote:
> On Wed, Sep 27, 2023 at 11:03:56PM +0200, Nirmoy Das wrote:
>> During resume, the steer semaphore on GT1 was observed to be held. The
>> hardware team has confirmed the safety of clearing the steer semaphore
>> during driver load/resume, as no lock acquisitions can occur in this
>> process by other agents.
> I guess the question is whether we just want to handle the one case
> where we've already seen a BIOS snapshot screw up (i.e., specifically on
> GT1 during resume), or do we want to make this a general sanitization
> that we do on both GTs at both load and resume, just to be safe?  Given
> that the hardware team has indicated no external agents would be
> expected to be using steering at the point the driver is
> loading/resuming, maybe it's best to always do the sanitization on
> platforms that have a hardware semaphore?

Agree, will make it got all GT.


Thanks,

Nirmoy

>
>
> Matt
>
>> v2: reset on resume not in intel_gt_init().
>> v3: do the reset on intel_gt_resume_early()
>>
>> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
>> ---
>>   drivers/gpu/drm/i915/gt/intel_gt_pm.c | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
>> index dab73980c9f1..59cebf205b72 100644
>> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.c
>> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
>> @@ -13,6 +13,7 @@
>>   #include "intel_engine_pm.h"
>>   #include "intel_gt.h"
>>   #include "intel_gt_clock_utils.h"
>> +#include "intel_gt_mcr.h"
>>   #include "intel_gt_pm.h"
>>   #include "intel_gt_print.h"
>>   #include "intel_gt_requests.h"
>> @@ -218,6 +219,17 @@ void intel_gt_pm_fini(struct intel_gt *gt)
>>   
>>   void intel_gt_resume_early(struct intel_gt *gt)
>>   {
>> +	/*
>> +	 * Reset the steer semaphore on GT1, as we have observed it
>> +	 * remaining held after a suspend operation. Confirmation
>> +	 * from the hardware team ensures the safety of resetting
>> +	 * the steer semaphore during driver load/resume, as there
>> +	 * are no lock acquisitions during this process by other
>> +	 * agents.
>> +	 */
>> +	if (MEDIA_VER(gt->i915) >= 13 && gt->type == GT_MEDIA)
>> +		intel_gt_mcr_lock_reset(gt);
>> +
>>   	intel_uncore_resume_early(gt->uncore);
>>   	intel_gt_check_and_clear_faults(gt);
>>   }
>> -- 
>> 2.41.0
>>