[Intel-gfx] [PATCH v1 1/1] drm/i915: Skip applying copy engine fuses

[Lucas De Marchi]

On Mon, Sep 12, 2022 at 06:59:53PM +0200, Andi Shyti wrote:
>Hi Lucas,
>
>On Mon, Sep 12, 2022 at 09:19:38AM -0700, Lucas De Marchi wrote:
>> Support for reading the fuses to check what are the Link Copy engines
>> was added in commit ad5f74f34201 ("drm/i915/pvc: read fuses for link
>> copy engines"). However they were added unconditionally because the
>> FUSE3 register is present since graphics version 10.
>>
>> However the bitfield with meml3 fuses only exists since graphics version
>> 12. Moreover, Link Copy engines are currently only available in PVC.
>> Tying additional copy engines to the meml3 fuses is not correct for
>> other platforms.
>>
>> Make sure there is a check for  `12.60 <= ver < 12.70`. Later platforms
>> may extend this function later if it's needed to fuse off copy engines.
>>
>> Currently it's harmless as the Link Copy engines are still not exported:
>> info->engine_mask only has BCS0 set and the register is only read for
>> platforms that do have it.
>>
>> Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
>>
>> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
>> index 814f83b5fe59..1f7188129cd1 100644
>> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
>> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
>> @@ -764,6 +764,10 @@ static void engine_mask_apply_copy_fuses(struct intel_gt *gt)
>>  	unsigned long meml3_mask;
>>  	unsigned long quad;
>>
>> +	if (!(GRAPHICS_VER_FULL(i915) >= IP_VER(12, 60) &&
>> +	      GRAPHICS_VER_FULL(i915) < IP_VER(12, 70)))
>> +		return;
>> +
>
>Isn't it easier if you wrote
>
>	if (GRAPHICS_VER_FULL(i915) < IP_VER(12, 60) ||
>	    GRAPHICS_VER_FULL(i915) >= IP_VER(12, 70))
>		return;
>
>?
>
>You save a parenthesis and a negation '!'.

but that makes it wrong. I'd really want the range
12.60 <= version < 12.70, so it applies to PVC  but is then disabled
again for MTL.  Depending on how this evolves for future platforms, we
may change it to a feature flag or just check by platform
name. For now I think this is the most future-proof option.

Lucas De Marchi

>
>Anyway, looks good:
>
>Reviewed-by: Andi Shyti <andi.shyti at linux.intel.com>
>
>Andi
>
>>  	meml3_mask = intel_uncore_read(gt->uncore, GEN10_MIRROR_FUSE3);
>>  	meml3_mask = REG_FIELD_GET(GEN12_MEML3_EN_MASK, meml3_mask);
>>
>>
>> --
>> b4 0.10.0-dev-df873