Re: [PATCH 02/22] drm/i915/icl: Enable Sampler DFR

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Fri, Apr 20, 2018 at 01:52:24PM -0700, Oscar Mateo wrote:
> 
> 
> On 04/20/2018 01:48 PM, Rodrigo Vivi wrote:
> > On Fri, Apr 20, 2018 at 01:33:46PM -0700, Oscar Mateo wrote:
> > > Sampler Dynamic Frequency Rebalancing (DFR) aims to reduce Sampler
> > > power by dynamically changing its clock frequency in low-throughput
> > > conditions. This patches enables it by default on Gen11.
> > > 
> > > v2: Wrong operation to clear the bit (Praveen)
> > > v3: Rebased on top of the WA refactoring
> > > 
> > > Cc: Praveen Paneri <praveen.paneri@intel.com>
> > > Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> > > Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
> > > Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
> > > ---
> > >   drivers/gpu/drm/i915/i915_reg.h          | 3 +++
> > >   drivers/gpu/drm/i915/intel_workarounds.c | 4 ++++
> > >   2 files changed, 7 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > > index f2ee225..4b7e6bc 100644
> > > --- a/drivers/gpu/drm/i915/i915_reg.h
> > > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > > @@ -8218,6 +8218,9 @@ enum {
> > >   #define GEN8_GARBCNTL                   _MMIO(0xB004)
> > >   #define   GEN9_GAPS_TSV_CREDIT_DISABLE  (1<<7)
> > > +#define GEN10_DFR_RATIO_EN_AND_CHICKEN	_MMIO(0x9550)
> > > +#define   DFR_DISABLE			(1 << 9)
> > > +
> > >   /* IVYBRIDGE DPF */
> > >   #define GEN7_L3CDERRST1(slice)		_MMIO(0xB008 + (slice) * 0x200) /* L3CD Error Status 1 */
> > >   #define   GEN7_L3CDERRST1_ROW_MASK	(0x7ff<<14)
> > > diff --git a/drivers/gpu/drm/i915/intel_workarounds.c b/drivers/gpu/drm/i915/intel_workarounds.c
> > > index 3f00623..60a5b1d 100644
> > > --- a/drivers/gpu/drm/i915/intel_workarounds.c
> > > +++ b/drivers/gpu/drm/i915/intel_workarounds.c
> > > @@ -692,6 +692,10 @@ static void icl_gt_workarounds_apply(struct drm_i915_private *dev_priv)
> > >   	I915_WRITE(_3D_CHICKEN3,
> > >   		   _MASKED_BIT_ENABLE(_3D_CHICKEN3_AA_LINE_QUALITY_FIX_ENABLE));
> > > +	/* This is not an Wa. Enable to reduce Sampler power */
> > First of all it is strange that a feature is under a chicken bit,
> 
> There is a precedent: _3D_CHICKEN3_AA_LINE_QUALITY_FIX_ENABLE

Oh, true!

Actually that never got same question from me because that
function is called init clock gating, although this function nowadays
is basically workarounds related to clock gatings :/)

> 
> > but if it is not an wa, but a PM feature, shouldn't we add it to some sort of
> > init clock gating function, or a new specific function called when it makes sense?
> 
> I'm open to suggestions

moving to clock gating is an option?
or needs to be called from context?

> 
> > > +	I915_WRITE(GEN10_DFR_RATIO_EN_AND_CHICKEN,
> > > +		   (I915_READ(GEN10_DFR_RATIO_EN_AND_CHICKEN) & ~DFR_DISABLE));
> > > +
> > >   	/* WaInPlaceDecompressionHang:icl */
> > >   	I915_WRITE(GEN9_GAMT_ECO_REG_RW_IA, (I915_READ(GEN9_GAMT_ECO_REG_RW_IA) |
> > >   					     GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS));
> > > -- 
> > > 1.9.1
> > > 
> > > _______________________________________________
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> > > Intel-gfx@lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
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