[Intel-gfx] [PATCH] drm/i915: Work around for underrun when enabling pipe scaler in GLK

[Ander Conselvan De Oliveira]

On Wed, 2017-05-24 at 13:57 +0530, Mahesh Kumar wrote:
> Hi,
> 
> 
> On Monday 08 May 2017 02:20 PM, Ander Conselvan de Oliveira wrote:
> > In Geminilake, a FIFO underrun happens the first time a pipe scaler is
> > enabled after boot/resume from suspend. Disabling DPF clock gating in
> > the respective CLKGATE_DIS_PSL register prior to enabling the scaler
> > works around the issue.
> 
> Is BSpec link or workaround number available for this?

This is not a documented workaround yet, still need input from hw engineers.

Ander


> 
> -Mahesh
> > Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira at intel.com>
> > ---
> >   drivers/gpu/drm/i915/i915_reg.h      |  8 ++++++++
> >   drivers/gpu/drm/i915/intel_display.c | 17 +++++++++++++++++
> >   2 files changed, 25 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index 524fdfd..3157c39 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -3424,6 +3424,14 @@ enum {
> >   #define   PWM2_GATING_DIS		(1 << 14)
> >   #define   PWM1_GATING_DIS		(1 << 13)
> >   
> > +#define _CLKGATE_DIS_PSL_A		0x46520
> > +#define _CLKGATE_DIS_PSL_B		0x46524
> > +#define _CLKGATE_DIS_PSL_C		0x46528
> > +#define   DPF_GATING_DIS		(1 << 10)
> > +
> > +#define CLKGATE_DIS_PSL(pipe) \
> > +	_MMIO_PIPE(pipe, _CLKGATE_DIS_PSL_A, _CLKGATE_DIS_PSL_B)
> > +
> >   /*
> >    * Display engine regs
> >    */
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 85b9e2f5..c24acdd 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -3176,6 +3176,7 @@ static void skl_detach_scaler(struct intel_crtc *intel_crtc, int id)
> >   static void skl_detach_scalers(struct intel_crtc *intel_crtc)
> >   {
> >   	struct intel_crtc_scaler_state *scaler_state;
> > +	struct drm_i915_private *dev_priv = to_i915(intel_crtc->base.dev);
> >   	int i;
> >   
> >   	scaler_state = &intel_crtc->config->scaler_state;
> > @@ -3185,6 +3186,14 @@ static void skl_detach_scalers(struct intel_crtc *intel_crtc)
> >   		if (!scaler_state->scalers[i].in_use)
> >   			skl_detach_scaler(intel_crtc, i);
> >   	}
> > +
> > +	if (IS_GEMINILAKE(dev_priv)) {
> > +		u32 tmp;
> > +
> > +		tmp = I915_READ(CLKGATE_DIS_PSL(intel_crtc->pipe));
> > +		tmp &= ~DPF_GATING_DIS;
> > +		I915_WRITE(CLKGATE_DIS_PSL(intel_crtc->pipe), tmp);
> > +	}
> >   }
> >   
> >   u32 skl_plane_stride(const struct drm_framebuffer *fb, int plane,
> > @@ -4763,6 +4772,14 @@ static void skylake_pfit_enable(struct intel_crtc *crtc)
> >   		if (WARN_ON(crtc->config->scaler_state.scaler_id < 0))
> >   			return;
> >   
> > +		if (IS_GEMINILAKE(dev_priv)) {
> > +			u32 tmp;
> > +
> > +			tmp = I915_READ(CLKGATE_DIS_PSL(crtc->pipe));
> > +			tmp |= DPF_GATING_DIS;
> > +			I915_WRITE(CLKGATE_DIS_PSL(crtc->pipe), tmp);
> > +		}
> > +
> >   		id = scaler_state->scaler_id;
> >   		I915_WRITE(SKL_PS_CTRL(pipe, id), PS_SCALER_EN |
> >   			PS_FILTER_MEDIUM | scaler_state->scalers[id].mode);
> 
>