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

Paulo Zanoni
2018-01-26T20:50:34Z

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.

>
> > +
> > + 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
> >
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