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

[Daniel Vetter <daniel@ffwll.ch>]

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
http://blog.ffwll.ch
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