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

Daniel Vetter
2015-10-30T16:00:46Z

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.

>
> - /* 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.

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
>
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--
Daniel Vetter
Software Engineer, Intel Corporation