Re: [PATCH 04/17] drm/i915/icl: Enable both DBuf slices during init

[Paulo Zanoni <paulo.r.zanoni@intel.com>]

Em Sex, 2018-01-26 às 18:50 -0200, Paulo Zanoni escreveu:
> Em Ter, 2018-01-23 às 16:49 -0800, James Ausmus escreveu:
> > On Tue, Jan 23, 2018 at 05:05:23PM -0200, Paulo Zanoni wrote:
> > > From: Mahesh Kumar <mahesh1.kumar@intel.com>
> > > 
> > > ICL has 2 slices of DBuf, enable both the slices during display
> > > init.
> > > 
> > > Ideally we should only enable the second slice when needed in
> > > order
> > > to
> > > save power, but while we're not there yet, adopt the simpler
> > > solution
> > > to keep us bug-free.
> > > 
> > > v2 (from Paulo):
> > >   - Add the TODO comment.
> > >   - Reorganize where things are defined.
> > >   - Fix indentation.
> > >   - Remove unnecessary POSTING_READ() calls.
> > >   - Improve the commit message.
> > > 
> > > Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
> > > Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_reg.h         |  2 ++
> > >  drivers/gpu/drm/i915/intel_runtime_pm.c | 34
> > > +++++++++++++++++++++++++++++++--
> > >  2 files changed, 34 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_reg.h
> > > b/drivers/gpu/drm/i915/i915_reg.h
> > > index 979bc06a59f4..1746df9a263d 100644
> > > --- a/drivers/gpu/drm/i915/i915_reg.h
> > > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > > @@ -7122,6 +7122,8 @@ enum {
> > >  #define  DISP_DATA_PARTITION_5_6	(1<<6)
> > >  #define  DISP_IPC_ENABLE		(1<<3)
> > >  #define DBUF_CTL	_MMIO(0x45008)
> > > +#define DBUF_CTL_S1	_MMIO(0x45008)
> > 
> > Since it's the exact same register, is it really worth duplicating,
> > or
> > should we just use the existing DBUF_CTL instead of adding
> > DBUF_CTL_S1?
> 
> I like it: it's just a single extra line on i915_reg.h and adds
> clarity
> to the code that uses it. But I have nothing against removing it too.
> 
> 
> > 
> > 
> > > +#define DBUF_CTL_S2	_MMIO(0x44FE8)
> > >  #define  DBUF_POWER_REQUEST		(1<<31)
> > >  #define  DBUF_POWER_STATE		(1<<30)
> > >  #define GEN7_MSG_CTL	_MMIO(0x45010)
> > > diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c
> > > b/drivers/gpu/drm/i915/intel_runtime_pm.c
> > > index 2556db16c76a..7801a425398f 100644
> > > --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> > > +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> > > @@ -2610,6 +2610,36 @@ static void gen9_dbuf_disable(struct
> > > drm_i915_private *dev_priv)
> > >  		DRM_ERROR("DBuf power disable timeout!\n");
> > >  }
> > >  
> > > +/*
> > > + * TODO: we shouldn't always enable DBUF_CTL_S2, we should only
> > > enable it when
> > > + * needed and keep it disabled as much as possible.
> > > + */
> > > +static void icl_dbuf_enable(struct drm_i915_private *dev_priv)
> > > +{
> > > +	I915_WRITE(DBUF_CTL_S1, I915_READ(DBUF_CTL_S1) |
> > > DBUF_POWER_REQUEST);
> > > +	I915_WRITE(DBUF_CTL_S2, I915_READ(DBUF_CTL_S2) |
> > > DBUF_POWER_REQUEST);
> > > +	POSTING_READ(DBUF_CTL_S2);
> > > +
> > > +	udelay(10);
> > 
> > BSpec says to poll, and timeout/fail after 10 uS, rather than
> > unconditionally busy wait - worth making more complex to
> > potentially
> > save a few uS of busy wait?
> 
> Yeah, good points. We have intel_wait_for_register() to help avoid
> the
> complexity here.

Oops, I realized this is just 10us. Our wait macros aren't helpful
here, the sleep is too small.

Also, these functions are modeled after skl_dbuf_{dis,en}enable, which
uses udelay too. We probably want to keep the same coding style for the
gen9 and the icl one.

So I think the best course is to keep the udelay, and if we come up
with a better solution we apply to the skl functions too.

With all that said, I guess my r-b patch on the patch stands.

> 
> 
> > 
> > > +
> > > +	if (!(I915_READ(DBUF_CTL_S1) & DBUF_POWER_STATE) ||
> > > +	    !(I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE))
> > > +		DRM_ERROR("DBuf power enable timeout\n");
> > > +}
> > > +
> > > +static void icl_dbuf_disable(struct drm_i915_private *dev_priv)
> > > +{
> > > +	I915_WRITE(DBUF_CTL_S1, I915_READ(DBUF_CTL_S1) &
> > > ~DBUF_POWER_REQUEST);
> > > +	I915_WRITE(DBUF_CTL_S2, I915_READ(DBUF_CTL_S2) &
> > > ~DBUF_POWER_REQUEST);
> > > +	POSTING_READ(DBUF_CTL_S2);
> > > +
> > > +	udelay(10);
> > > +
> > > +	if ((I915_READ(DBUF_CTL_S1) & DBUF_POWER_STATE) ||
> > > +	    (I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE))
> > > +		DRM_ERROR("DBuf power disable timeout!\n");
> > > +}
> > > +
> > >  static void skl_display_core_init(struct drm_i915_private
> > > *dev_priv,
> > >  				   bool resume)
> > >  {
> > > @@ -2920,7 +2950,7 @@ static void icl_display_core_init(struct
> > > drm_i915_private *dev_priv,
> > >  	icl_init_cdclk(dev_priv);
> > >  
> > >  	/* 6. Enable DBUF. */
> > > -	gen9_dbuf_enable(dev_priv);
> > > +	icl_dbuf_enable(dev_priv);
> > >  
> > >  	/* 7. Setup MBUS. */
> > >  	/* FIXME: MBUS code not here yet. */
> > > @@ -2940,7 +2970,7 @@ static void icl_display_core_uninit(struct
> > > drm_i915_private *dev_priv)
> > >  	/* 1. Disable all display engine functions -> aready
> > > done
> > > */
> > >  
> > >  	/* 2. Disable DBUF */
> > > -	gen9_dbuf_disable(dev_priv);
> > > +	icl_dbuf_disable(dev_priv);
> > >  
> > >  	/* 3. Disable CD clock */
> > >  	icl_uninit_cdclk(dev_priv);
> > > -- 
> > > 2.14.3
> > > 
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > Intel-gfx@lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
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