Re: [PATCH 13/14] drm/i915: Use intel_dp->DP in eDP PLL setup

Ville Syrjälä
2015-10-30T16:36:34Z

On Fri, Oct 30, 2015 at 05:00:42PM +0100, Daniel Vetter wrote:
> On Thu, Oct 29, 2015 at 09:26:02PM +0200, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > Use intel_dp->DP in the eDP PLL setup, instead of doing RMWs.
> >
> > To do this we need to move DP_AUDIO_OUTPUT_ENABLE setup to happen later,
> > so that we don't enable audio accidentally while configuring the PLL.
> >
> > Also intel_dp_link_down() must be made to update intel_dp->DP so that we
> > don't re-enable the port by accident when turning off the PLL. This is
> > safe now that we don't call intel_dp_link_down() during link retraining.
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> > drivers/gpu/drm/i915/intel_dp.c | 41 ++++++++++++++---------------------------
> > 1 file changed, 14 insertions(+), 27 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index e259803..63659e7 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -1548,23 +1548,18 @@ static void ironlake_set_pll_cpu_edp(struct intel_dp *intel_dp)
> > struct intel_crtc *crtc = to_intel_crtc(dig_port->base.base.crtc);
> > struct drm_device *dev = crtc->base.dev;
> > struct drm_i915_private *dev_priv = dev->dev_private;
> > - u32 dpa_ctl;
> >
> > DRM_DEBUG_KMS("eDP PLL enable for clock %d\n",
> > crtc->config->port_clock);
> > - dpa_ctl = I915_READ(DP_A);
> > - dpa_ctl &= ~DP_PLL_FREQ_MASK;
> >
> > - if (crtc->config->port_clock == 162000) {
> > - dpa_ctl |= DP_PLL_FREQ_162MHZ;
> > + intel_dp->DP &= ~DP_PLL_FREQ_MASK;
> > +
> > + if (crtc->config->port_clock == 162000)
> > intel_dp->DP |= DP_PLL_FREQ_162MHZ;
> > - } else {
> > - dpa_ctl |= DP_PLL_FREQ_270MHZ;
> > + else
> > intel_dp->DP |= DP_PLL_FREQ_270MHZ;
> > - }
> > -
> > - I915_WRITE(DP_A, dpa_ctl);
> >
> > + I915_WRITE(DP_A, intel_dp->DP);
> > POSTING_READ(DP_A);
> > udelay(500);
> > }
> > @@ -1613,9 +1608,6 @@ static void intel_dp_prepare(struct intel_encoder *encoder)
> > intel_dp->DP |= DP_VOLTAGE_0_4 | DP_PRE_EMPHASIS_0;
> > intel_dp->DP |= DP_PORT_WIDTH(crtc->config->lane_count);
> >
> > - if (crtc->config->has_audio)
> > - intel_dp->DP |= DP_AUDIO_OUTPUT_ENABLE;
> > -
> > /* Split out the IBX/CPU vs CPT settings */
> >
> > if (IS_GEN7(dev) && port == PORT_A) {
> > @@ -2176,20 +2168,14 @@ static void ironlake_edp_pll_on(struct intel_dp *intel_dp)
> > struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> > struct intel_crtc *crtc = to_intel_crtc(intel_dig_port->base.base.crtc);
> > struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> > - u32 dpa_ctl;
> >
> > assert_pipe_disabled(dev_priv, crtc->pipe);
> > assert_dp_port_disabled(intel_dp);
> > assert_edp_pll_disabled(dev_priv);
> >
> > DRM_DEBUG_KMS("\n");
> > - dpa_ctl = I915_READ(DP_A);
> > -
> > - /* We don't adjust intel_dp->DP while tearing down the link, to
> > - * facilitate link retraining (e.g. after hotplug). Hence clear all
> > - * enable bits here to ensure that we don't enable too much. */
> > - intel_dp->DP &= ~(DP_PORT_EN | DP_AUDIO_OUTPUT_ENABLE);
> > intel_dp->DP |= DP_PLL_ENABLE;
> > +
> > I915_WRITE(DP_A, intel_dp->DP);
> > POSTING_READ(DP_A);
> > udelay(200);
> > @@ -2200,19 +2186,14 @@ static void ironlake_edp_pll_off(struct intel_dp *intel_dp)
> > struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> > struct intel_crtc *crtc = to_intel_crtc(intel_dig_port->base.base.crtc);
> > struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> > - u32 dpa_ctl;
> >
> > assert_pipe_disabled(dev_priv, crtc->pipe);
> > assert_dp_port_disabled(intel_dp);
> > assert_edp_pll_enabled(dev_priv);
> >
> > - dpa_ctl = I915_READ(DP_A);
> > + intel_dp->DP &= ~DP_PLL_ENABLE;
>
> I think we need to clear DP_AUDIO_OUTPUT_ENABLE here too, otherwise a dpms
> off->on cycle will again enable audio too early in edp_pll_on.

intel_dp_prepare() starts from scratch:
"intel_dp->DP = I915_READ(intel_dp->output_reg) & DP_DETECTED;"

>
> >
> > - /* We can't rely on the value tracked for the DP register in
> > - * intel_dp->DP because link_down must not change that (otherwise link
> > - * re-training will fail. */
> > - dpa_ctl &= ~DP_PLL_ENABLE;
> > - I915_WRITE(DP_A, dpa_ctl);
> > + I915_WRITE(DP_A, intel_dp->DP);
> > POSTING_READ(DP_A);
> > udelay(200);
> > }
> > @@ -2568,6 +2549,8 @@ static void intel_dp_enable_port(struct intel_dp *intel_dp)
> > {
> > struct drm_device *dev = intel_dp_to_dev(intel_dp);
> > struct drm_i915_private *dev_priv = dev->dev_private;
> > + struct intel_crtc *crtc =
> > + to_intel_crtc(dp_to_dig_port(intel_dp)->base.base.crtc);
> >
> > /* enable with pattern 1 (as per spec) */
> > _intel_dp_set_link_train(intel_dp, &intel_dp->DP,
> > @@ -2583,6 +2566,8 @@ static void intel_dp_enable_port(struct intel_dp *intel_dp)
> > * fail when the power sequencer is freshly used for this port.
> > */
> > intel_dp->DP |= DP_PORT_EN;
> > + if (crtc->config->has_audio)
> > + intel_dp->DP |= DP_AUDIO_OUTPUT_ENABLE;
>
> If I read the code correctly before this patch the I915_WRITE right above
> this one here already enabled the audio bit. Shouldn't matter, and
> probably better, but must be mentioned in the commit message.

Indeed. The new order even makes more sense. I'll add a note.

>
> With these two things addressed:
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>
> >
> > I915_WRITE(intel_dp->output_reg, intel_dp->DP);
> > POSTING_READ(intel_dp->output_reg);
> > @@ -4028,6 +4013,8 @@ intel_dp_link_down(struct intel_dp *intel_dp)
> > }
> >
> > msleep(intel_dp->panel_power_down_delay);
> > +
> > + intel_dp->DP = DP;
> > }
> >
> > static bool
> > --
> > 2.4.10
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

--
Ville Syrjälä
Intel OTC