Re: [PATCH 2/4] drm/i915: Clean up L3 SQC register field definitions

[Imre Deak <imre.deak@intel.com>]

On ti, 2016-04-26 at 12:03 +0300, Imre Deak wrote:
> On ti, 2016-04-26 at 11:11 +0300, Mika Kuoppala wrote:
> > Imre Deak <imre.deak@intel.com> writes:
> > 
> > > [ text/plain ]
> > > No need for hard-coding the register value, the corresponding
> > > fields are
> > > defined properly in BSpec.
> > > 
> > > No functional change.
> > > 
> > > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_reg.h | 3 ++-
> > >  drivers/gpu/drm/i915/intel_pm.c | 3 ++-
> > >  2 files changed, 4 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_reg.h
> > > b/drivers/gpu/drm/i915/i915_reg.h
> > > index c21b71c..0cb2e17 100644
> > > --- a/drivers/gpu/drm/i915/i915_reg.h
> > > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > > @@ -6073,7 +6073,8 @@ enum skl_disp_power_wells {
> > >  #define  VLV_B0_WA_L3SQCREG1_VALUE		0x00D30000
> > >  
> > >  #define GEN8_L3SQCREG1				_MMIO(0xB100
> > > )
> > > -#define  BDW_WA_L3SQCREG1_DEFAULT		0x784000
> > > +#define  L3_GENERAL_PRIO_CREDITS(x)		(((x) >> 1) <<
> > > 19)
> > > +#define  L3_HIGH_PRIO_CREDITS(x)		(((x) >> 1) << 14)
> > >  
> > 
> > The values listed for CHV it seems that the macros would produce
> > one less than intended. For example chv 34 -> 0b10010
> 
> Yes, Ville noticed this too. I assumed the same formula as used on the
> other platforms (BDW, SKL, BXT) and haven't noticed the difference wrt.
> CHV.
> 
> According to Ville's tests using the formula in the spec (and setting
> the new credits 30, 2) leads to a hang. So my suspicion is that it's a

Sorry, I meant setting the new credits 38, 2.

> bug in the spec, I will file a change request there.
> 
> --Imre
> 
> > 
> > -Mika
> > 
> > 
> > >  #define GEN7_L3CNTLREG1				_MMIO(0xB01
> > > C)
> > >  #define  GEN7_WA_FOR_GEN7_L3_CONTROL			0x3C47
> > > FF8C
> > > diff --git a/drivers/gpu/drm/i915/intel_pm.c
> > > b/drivers/gpu/drm/i915/intel_pm.c
> > > index a6fd4dd..a9b7626 100644
> > > --- a/drivers/gpu/drm/i915/intel_pm.c
> > > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > > @@ -6710,7 +6710,8 @@ static void
> > > broadwell_init_clock_gating(struct drm_device *dev)
> > >  	 */
> > >  	misccpctl = I915_READ(GEN7_MISCCPCTL);
> > >  	I915_WRITE(GEN7_MISCCPCTL, misccpctl &
> > > ~GEN7_DOP_CLOCK_GATE_ENABLE);
> > > -	I915_WRITE(GEN8_L3SQCREG1, BDW_WA_L3SQCREG1_DEFAULT);
> > > +	I915_WRITE(GEN8_L3SQCREG1, L3_GENERAL_PRIO_CREDITS(30) |
> > > +				   L3_HIGH_PRIO_CREDITS(2));
> > >  	/*
> > >  	 * Wait at least 100 clocks before re-enabling clock
> > > gating. See
> > >  	 * the definition of L3SQCREG1 in BSpec.
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