Re: [PATCH 09/14] drm/i915: Hide underruns from eDP PLL and port enable on ILK

Jesse Barnes
2015-10-29T19:39:18Z

On 10/29/2015 12:25 PM, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> We get underruns on the other pipe when enabling the CPU eDP PLL and
> port on ILK.
>
> Bspec knows about the PLL issue, and recommends doing a vblank wait just
> prior to enabling the PLL. That does seem to help, but unfortunately we
> get another underrun when actually enabling the CPU eDP port. Bspec
> doesn't mention that at all, and the same vblank wait trick doesn't
> appear to be effective there.
>
> Since I have no better clue how to deal with this, just hide the errors.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 34 +++++++++++++++++++++++++++++++---
> 1 file changed, 31 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 4a0fb63..0b9b440 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -2575,6 +2575,8 @@ static void intel_enable_dp(struct intel_encoder *encoder)
> struct drm_i915_private *dev_priv = dev->dev_private;
> struct intel_crtc *crtc = to_intel_crtc(encoder->base.crtc);
> uint32_t dp_reg = I915_READ(intel_dp->output_reg);
> + enum port port = dp_to_dig_port(intel_dp)->port;
> + enum pipe pipe = crtc->pipe;
>
> if (WARN_ON(dp_reg & DP_PORT_EN))
> return;
> @@ -2586,6 +2588,17 @@ static void intel_enable_dp(struct intel_encoder *encoder)
>
> intel_dp_enable_port(intel_dp);
>
> + if (port == PORT_A && IS_GEN5(dev_priv)) {
> + /*
> + * Underrun reporting for the other pipe was disabled in
> + * g4x_pre_enable_dp(). The eDP PLL and port have now been
> + * enabled, so it's now safe to re-enable underrun reporting.
> + */
> + intel_wait_for_vblank_if_active(dev_priv->dev, !pipe);
> + intel_set_cpu_fifo_underrun_reporting(dev_priv, !pipe, true);
> + intel_set_pch_fifo_underrun_reporting(dev_priv, !pipe, true);
> + }
> +
> edp_panel_vdd_on(intel_dp);
> edp_panel_on(intel_dp);
> edp_panel_vdd_off(intel_dp, true);
> @@ -2608,7 +2621,7 @@ static void intel_enable_dp(struct intel_encoder *encoder)
>
> if (crtc->config->has_audio) {
> DRM_DEBUG_DRIVER("Enabling DP audio on pipe %c\n",
> - pipe_name(crtc->pipe));
> + pipe_name(pipe));
> intel_audio_codec_enable(encoder);
> }
> }
> @@ -2631,13 +2644,28 @@ static void vlv_enable_dp(struct intel_encoder *encoder)
>
> static void g4x_pre_enable_dp(struct intel_encoder *encoder)
> {
> + struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> - struct intel_digital_port *dport = dp_to_dig_port(intel_dp);
> + enum port port = dp_to_dig_port(intel_dp)->port;
> + enum pipe pipe = to_intel_crtc(encoder->base.crtc)->pipe;
>
> intel_dp_prepare(encoder);
>
> + if (port == PORT_A && IS_GEN5(dev_priv)) {
> + /*
> + * We get FIFO underruns on the other pipe when
> + * enabling the CPU eDP PLL, and when enabling CPU
> + * eDP port. We could potentially avoid the PLL
> + * underrun with a vblank wait just prior to enabling
> + * the PLL, but that doesn't appear to help the port
> + * enable case. Just sweep it all under the rug.
> + */
> + intel_set_cpu_fifo_underrun_reporting(dev_priv, !pipe, false);
> + intel_set_pch_fifo_underrun_reporting(dev_priv, !pipe, false);
> + }
> +
> /* Only ilk+ has port A */
> - if (dport->port == PORT_A) {
> + if (port == PORT_A) {
> ironlake_set_pll_cpu_edp(intel_dp);
> ironlake_edp_pll_on(intel_dp);
> }
>

Wish we had a nice hook to hide the gen5 bits somewhere better, but it's
fine as is with the comment.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>