Re: [Intel-gfx] [PATCH 1/2] drm/i915: Don't use DRM_DEBUG_WARN_ON for unexpected l3bank/mslice config

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 04/05/2022 17:48, Matt Roper wrote:
> On Wed, May 04, 2022 at 01:07:14PM +0100, Tvrtko Ursulin wrote:
>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>
>> DRM_DEBUG_WARN_ON should only be used when we are certain CI is guaranteed
>> to exercise a certain code path, so in case of values coming from MMIO
>> reads we cannot be sure CI will have all the possible SKUs and parts.
>>
>> Use drm_warn instead and move logging to init phase while at it.
> 
> Changing to drm_warn looks good, although moving the location changes
> the intent a bit; I think originally the idea was to warn if we were
> trying to do a steering lookup for a type that we never initialized
> (e.g., an LNCF lookup for a !HAS_MSLICES platform where we never even
> read the register in the first place).  But I don't think we've ever
> made a mistake that would cause us to trip the warning, so it probably
> isn't terribly important to keep it there.

Ah I see.. there we could put something like:

	case MSLICE:
		GEM_WARN_ON(!HAS_MSLICES(...));

?

Regards,

Tvrtko

> 
> Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
> 
>>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>> Cc: Matt Roper <matthew.d.roper@intel.com>
>> Cc: Jani Nikula <jani.nikula@intel.com>
>> ---
>>   drivers/gpu/drm/i915/gt/intel_gt.c | 13 ++++++-------
>>   1 file changed, 6 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
>> index 53307ca0eed0..c474e5c3ea5e 100644
>> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
>> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
>> @@ -153,11 +153,14 @@ int intel_gt_init_mmio(struct intel_gt *gt)
>>   	 * An mslice is unavailable only if both the meml3 for the slice is
>>   	 * disabled *and* all of the DSS in the slice (quadrant) are disabled.
>>   	 */
>> -	if (HAS_MSLICES(i915))
>> +	if (HAS_MSLICES(i915)) {
>>   		gt->info.mslice_mask =
>>   			slicemask(gt, GEN_DSS_PER_MSLICE) |
>>   			(intel_uncore_read(gt->uncore, GEN10_MIRROR_FUSE3) &
>>   			 GEN12_MEML3_EN_MASK);
>> +		if (!gt->info.mslice_mask) /* should be impossible! */
>> +			drm_warn(&i915->drm, "mslice mask all zero!\n");
>> +	}
>>   
>>   	if (IS_DG2(i915)) {
>>   		gt->steering_table[MSLICE] = xehpsdv_mslice_steering_table;
>> @@ -171,6 +174,8 @@ int intel_gt_init_mmio(struct intel_gt *gt)
>>   		gt->info.l3bank_mask =
>>   			~intel_uncore_read(gt->uncore, GEN10_MIRROR_FUSE3) &
>>   			GEN10_L3BANK_MASK;
>> +		if (!gt->info.l3bank_mask) /* should be impossible! */
>> +			drm_warn(&i915->drm, "L3 bank mask is all zero!\n");
>>   	} else if (HAS_MSLICES(i915)) {
>>   		MISSING_CASE(INTEL_INFO(i915)->platform);
>>   	}
>> @@ -882,20 +887,14 @@ static void intel_gt_get_valid_steering(struct intel_gt *gt,
>>   {
>>   	switch (type) {
>>   	case L3BANK:
>> -		GEM_DEBUG_WARN_ON(!gt->info.l3bank_mask); /* should be impossible! */
>> -
>>   		*sliceid = 0;		/* unused */
>>   		*subsliceid = __ffs(gt->info.l3bank_mask);
>>   		break;
>>   	case MSLICE:
>> -		GEM_DEBUG_WARN_ON(!gt->info.mslice_mask); /* should be impossible! */
>> -
>>   		*sliceid = __ffs(gt->info.mslice_mask);
>>   		*subsliceid = 0;	/* unused */
>>   		break;
>>   	case LNCF:
>> -		GEM_DEBUG_WARN_ON(!gt->info.mslice_mask); /* should be impossible! */
>> -
>>   		/*
>>   		 * An LNCF is always present if its mslice is present, so we
>>   		 * can safely just steer to LNCF 0 in all cases.
>> -- 
>> 2.32.0
>>
>