On Fri, Oct 14, 2016 at 07:27:39PM +0000, Pandiyan, Dhinakaran wrote: > On Thu, 2016-10-13 at 11:30 -0700, Jim Bride wrote: > > On Thu, Oct 13, 2016 at 11:04:19AM -0700, Dhinakaran Pandiyan wrote: > > > According to BSpec, cdclk has to be not less than 432 MHz with DP audio > > > enabled, port width x4, and link rate HBR2 (5.4 GHz) > > > > > > Having a lower cdclk triggers pipe underruns, which then lead to displays > > > continuously cycling off and on. This is essential for DP MST audio as the > > > link is trained at HBR2 and 4 lanes by default. > > > > > > This should fix https://bugs.freedesktop.org/show_bug.cgi?id=97907 > > > > > > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx> > > > --- > > > drivers/gpu/drm/i915/intel_display.c | 47 +++++++++++++++++++++++++++++++++--- > > > 1 file changed, 43 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c > > > index cfcb03f..6a05183 100644 > > > --- a/drivers/gpu/drm/i915/intel_display.c > > > +++ b/drivers/gpu/drm/i915/intel_display.c > > > @@ -6603,14 +6603,43 @@ static int valleyview_modeset_calc_cdclk(struct drm_atomic_state *state) > > > return 0; > > > } > > > > > > +static bool cdclk_min_for_dp_audio(struct drm_atomic_state *state) > > > +{ > > > + > > > + struct drm_crtc_state *crtc_state; > > > + struct drm_crtc *crtc; > > > + int i; > > > + > > > + /* BSpec says "Do not use DisplayPort with CDCLK less than 432 MHz, > > > + * audio enabled, port width x4, and link rate HBR2 (5.4 GHz), or else > > > + * there may be audio corruption or screen corruption." > > > + */ > > > > It's probably worth mentioning that this limitation really only applies for > > SKL (at least that I can see) and BXT A (which I don't think we even care > > about anymore since it's not a production part.) Were we seeing underruns > > on non-SKL platforms that increasing CDCLK fixed? In any event, I'd rather > > see this only implemented for SKL (see BDW code below) unless we've empirically > > noticed a similar problem on BDW (or the B-Spec says something about this and I > > missed it.) > > > > Jim > > > > > Yes, Libin saw the problem when testing a BDW NUC. And, the patch is > applicable to BDW according to the BSpec. I will try to get a > confirmation on whether this is needed BXT production parts. Please also check docs for hsw, that's where dp mst support started. -Daniel > > > > + > > > + for_each_crtc_in_state(state, crtc, crtc_state, i) { > > > + struct intel_crtc_state *pipe_config = > > > + to_intel_crtc_state(crtc_state); > > > + > > > + return (intel_crtc_has_dp_encoder(pipe_config) && > > > + pipe_config->has_audio && > > > + pipe_config->port_clock == 540000 && > > > + pipe_config->lane_count == 4); > > > + } > > > + > > > + return false; > > > +} > > > + > > > static int bxt_modeset_calc_cdclk(struct drm_atomic_state *state) > > > { > > > int max_pixclk = ilk_max_pixel_rate(state); > > > + int cdclk, min_cdclk = 0; > > > struct intel_atomic_state *intel_state = > > > to_intel_atomic_state(state); > > > > > > - intel_state->cdclk = intel_state->dev_cdclk = > > > - bxt_calc_cdclk(max_pixclk); > > > + if (cdclk_min_for_dp_audio(state)) > > > + min_cdclk = bxt_calc_cdclk(432000); > > > + > > > + cdclk = bxt_calc_cdclk(max_pixclk); > > > + intel_state->cdclk = intel_state->dev_cdclk = max(min_cdclk, cdclk); > > > > > > if (!intel_state->active_crtcs) > > > intel_state->dev_cdclk = bxt_calc_cdclk(0); > > > @@ -10374,7 +10403,10 @@ static int broadwell_modeset_calc_cdclk(struct drm_atomic_state *state) > > > struct drm_i915_private *dev_priv = to_i915(state->dev); > > > struct intel_atomic_state *intel_state = to_intel_atomic_state(state); > > > int max_pixclk = ilk_max_pixel_rate(state); > > > - int cdclk; > > > + int cdclk, min_cdclk = 0; > > > + > > > + if (cdclk_min_for_dp_audio(state)) > > > + min_cdclk = broadwell_calc_cdclk(432000); > > > > > > /* > > > * FIXME should also account for plane ratio > > > @@ -10382,6 +10414,8 @@ static int broadwell_modeset_calc_cdclk(struct drm_atomic_state *state) > > > */ > > > cdclk = broadwell_calc_cdclk(max_pixclk); > > > > > > + cdclk = max(min_cdclk, cdclk); > > > + > > > if (cdclk > dev_priv->max_cdclk_freq) { > > > DRM_DEBUG_KMS("requested cdclk (%d kHz) exceeds max (%d kHz)\n", > > > cdclk, dev_priv->max_cdclk_freq); > > > @@ -10411,7 +10445,10 @@ static int skl_modeset_calc_cdclk(struct drm_atomic_state *state) > > > struct drm_i915_private *dev_priv = to_i915(state->dev); > > > const int max_pixclk = ilk_max_pixel_rate(state); > > > int vco = intel_state->cdclk_pll_vco; > > > - int cdclk; > > > + int cdclk, min_cdclk = 0; > > > + > > > + if (cdclk_min_for_dp_audio(state)) > > > + min_cdclk = skl_calc_cdclk(432000, vco); > > > > > > /* > > > * FIXME should also account for plane ratio > > > @@ -10419,6 +10456,8 @@ static int skl_modeset_calc_cdclk(struct drm_atomic_state *state) > > > */ > > > cdclk = skl_calc_cdclk(max_pixclk, vco); > > > > > > + cdclk = max(min_cdclk, cdclk); > > > + > > > /* > > > * FIXME move the cdclk caclulation to > > > * compute_config() so we can fail gracegully. > > > -- > > > 2.7.4 > > _______________________________________________ > > Intel-gfx mailing list > > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
