Re: [Intel-gfx] [PATCH v2] drm/i915: Try to sanitize bogus DPLL state left over by broken SNB BIOSen

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Jan 28, 2019 at 09:30:35AM +0000, Kahola, Mika wrote:
> The patch look ok to me.
> 
> On Fri, 2019-01-11 at 19:49 +0200, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Certain SNB machines (eg. ASUS K53SV) seem to have a broken BIOS
> > which misprograms the hardware badly when encountering a suitably
> > high resolution display. The programmed pipe timings are somewhat
> > bonkers and the DPLL is totally misprogrammed (P divider == 0).
> > That will result in atomic commit timeouts as apparently the pipe
> > is sufficiently stuck to not signal vblank interrupts.
> > 
> > IIRC something like this was also observed on some other SNB
> > machine years ago (might have been a Dell XPS 8300) but a BIOS
> > update cured it. Sadly looks like this was never fixed for the
> > ASUS K53SV as the latest BIOS (K53SV.320 11/11/2011) is still
> > broken.
> > 
> > The quickest way to deal with this seems to be to shut down
> > the pipe+ports+DPLL. Unfortunately doing this during the
> > normal sanitization phase isn't quite soon enough as we
> > already spew several WARNs about the bogus hardware state.
> > But it's better than hanging the boot for a few dozen seconds.
> > Since this is limited to a few old machines it doesn't seem
> > entirely worthwile to try and rework the readout+sanitization
> > code to handle it more gracefully.
> > 
> > v2: Fix potential NULL deref (kbuild test robot)
> >     Constify has_bogus_dpll_config()
> > 
> > Cc: stable@vger.kernel.org # v4.20+
> > Cc: Daniel Kamil Kozar <dkk089@gmail.com>
> > Reported-by: Daniel Kamil Kozar <dkk089@gmail.com>
> > Tested-by: Daniel Kamil Kozar <dkk089@gmail.com>
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109245
> > Fixes: 516a49cc1946 ("drm/i915: Fix assert_plane() warning on bootup
> > with external display")
> 
> Reviewed-by: Mika Kahola <mika.kahola@intel.com>

Thanks. Pushed to dinq.

> 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 50 ++++++++++++++++++++++++
> > ----
> >  1 file changed, 44 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > b/drivers/gpu/drm/i915/intel_display.c
> > index 5dc0de89c49e..6cd6048b4731 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -15438,16 +15438,45 @@ static void intel_sanitize_crtc(struct
> > intel_crtc *crtc,
> >  	}
> >  }
> >  
> > +static bool has_bogus_dpll_config(const struct intel_crtc_state
> > *crtc_state)
> > +{
> > +	struct drm_i915_private *dev_priv = to_i915(crtc_state-
> > >base.crtc->dev);
> > +
> > +	/*
> > +	 * Some SNB BIOSen (eg. ASUS K53SV) are known to misprogram
> > +	 * the hardware when a high res displays plugged in. DPLL P
> > +	 * divider is zero, and the pipe timings are bonkers. We'll
> > +	 * try to disable everything in that case.
> > +	 *
> > +	 * FIXME would be nice to be able to sanitize this state
> > +	 * without several WARNs, but for now let's take the easy
> > +	 * road.
> > +	 */
> > +	return IS_GEN(dev_priv, 6) &&
> > +		crtc_state->base.active &&
> > +		crtc_state->shared_dpll &&
> > +		crtc_state->port_clock == 0;
> > +}
> > +
> >  static void intel_sanitize_encoder(struct intel_encoder *encoder)
> >  {
> >  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> >  	struct intel_connector *connector;
> > +	struct intel_crtc *crtc = to_intel_crtc(encoder->base.crtc);
> > +	struct intel_crtc_state *crtc_state = crtc ?
> > +		to_intel_crtc_state(crtc->base.state) : NULL;
> >  
> >  	/* We need to check both for a crtc link (meaning that the
> >  	 * encoder is active and trying to read from a pipe) and the
> >  	 * pipe itself being active. */
> > -	bool has_active_crtc = encoder->base.crtc &&
> > -		to_intel_crtc(encoder->base.crtc)->active;
> > +	bool has_active_crtc = crtc_state &&
> > +		crtc_state->base.active;
> > +
> > +	if (crtc_state && has_bogus_dpll_config(crtc_state)) {
> > +		DRM_DEBUG_KMS("BIOS has misprogrammed the hardware.
> > Disabling pipe %c\n",
> > +			      pipe_name(crtc->pipe));
> > +		has_active_crtc = false;
> > +	}
> >  
> >  	connector = intel_encoder_find_connector(encoder);
> >  	if (connector && !has_active_crtc) {
> > @@ -15458,16 +15487,25 @@ static void intel_sanitize_encoder(struct
> > intel_encoder *encoder)
> >  		/* Connector is active, but has no active pipe. This is
> >  		 * fallout from our resume register restoring. Disable
> >  		 * the encoder manually again. */
> > -		if (encoder->base.crtc) {
> > -			struct drm_crtc_state *crtc_state = encoder-
> > >base.crtc->state;
> > +		if (crtc_state) {
> > +			struct drm_encoder *best_encoder;
> >  
> >  			DRM_DEBUG_KMS("[ENCODER:%d:%s] manually
> > disabled\n",
> >  				      encoder->base.base.id,
> >  				      encoder->base.name);
> > +
> > +			/* avoid oopsing in case the hooks consult
> > best_encoder */
> > +			best_encoder = connector->base.state-
> > >best_encoder;
> > +			connector->base.state->best_encoder = &encoder-
> > >base;
> > +
> >  			if (encoder->disable)
> > -				encoder->disable(encoder,
> > to_intel_crtc_state(crtc_state), connector->base.state);
> > +				encoder->disable(encoder, crtc_state,
> > +						 connector-
> > >base.state);
> >  			if (encoder->post_disable)
> > -				encoder->post_disable(encoder,
> > to_intel_crtc_state(crtc_state), connector->base.state);
> > +				encoder->post_disable(encoder,
> > crtc_state,
> > +						      connector-
> > >base.state);
> > +
> > +			connector->base.state->best_encoder =
> > best_encoder;
> >  		}
> >  		encoder->base.crtc = NULL;
> >  

-- 
Ville Syrjälä
Intel