Re: [PATCH] drm/i915/bdw: WaProgramL3SqcReg1Default

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Rodrigo Vivi <rodrigo.vivi@intel.com> writes:

> Program the default initial value of the L3SqcReg1 on BDW for performance
>
> v2: Default confirmed and using intel_ring_emit_wa as Mika pointed out.
>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h         | 3 +++
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 5 ++++-
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 36a847a..33143cc 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -4972,6 +4972,9 @@ enum punit_power_well {
>  #define GEN7_L3SQCREG1				0xB010
>  #define  VLV_B0_WA_L3SQCREG1_VALUE		0x00D30000
>  
> +#define GEN8_L3SQCREG1				0xB100
> +#define  BDW_WA_L3SQCREG1_DEFAULT		0x00610000
> +

This is the default value after reset. I have experimented with other
values and nothing improves above noise level. Further, my suggestion to
using 0x00810000 will cause a gpu hang...so there is dragons here.

As you are writing the same default value that is already in register,
and there is no indication that we should refresh anything, I would
say this patch is not needed until someone comes along and shows
something better than what the default is.

Thanks,
-Mika

>  #define GEN7_L3CNTLREG1				0xB01C
>  #define  GEN7_WA_FOR_GEN7_L3_CONTROL			0x3C47FF8C
>  #define  GEN7_L3AGDIS				(1<<19)
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 816a692..a37675d 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -707,7 +707,7 @@ static int bdw_init_workarounds(struct intel_engine_cs *ring)
>  	 * update the number of dwords required based on the
>  	 * actual number of workarounds applied
>  	 */
> -	ret = intel_ring_begin(ring, 18);
> +	ret = intel_ring_begin(ring, 21);
>  	if (ret)
>  		return ret;
>  
> @@ -751,6 +751,9 @@ static int bdw_init_workarounds(struct intel_engine_cs *ring)
>  	intel_ring_emit_wa(ring, GEN7_GT_MODE,
>  			   GEN6_WIZ_HASHING_MASK | GEN6_WIZ_HASHING_16x4);
>  
> +	/* WaProgramL3SqcReg1Default:bdw */
> +	intel_ring_emit_wa(ring, GEN8_L3SQCREG1, BDW_WA_L3SQCREG1_DEFAULT);
> +
>  	intel_ring_advance(ring);
>  
>  	DRM_DEBUG_DRIVER("Number of Workarounds applied: %d\n",
> -- 
> 1.9.3
>
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