drm/i915: Use the fixed pixel clock for eDP in intel_dp_set_m_n()

The eDP output on HP Z1 is still broken when X is started even after
fixing the infinite link-train loop.  The regression was introduced in
3.6 kernel for cleaning up the mode clock handling code in intel_dp.c
by the commit [71244653: drm/i915: adjusted_mode->clock in the dp
mode_fix].

In the past, the clock of the reference mode was modified in
intel_dp_mode_fixup() in the case of eDP fixed clock, and this clock was
used for calculating in intel_dp_set_m_n().  This override was removed,
thus the wrong mode clock is used for the calculation, resulting in a
psychedelic smoking output in the end.

This patch corrects the clock to be used in the place.

v1->v2: Use intel_edp_target_clock() for checking eDP fixed clock
instead of open code as in ironlake_set_m_n().

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 11 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index d46dde5a51e3..d7d4afe01341 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -820,6 +820,7 @@ intel_dp_set_m_n(struct drm_crtc *crtc, struct drm_display_mode *mode,
         struct intel_link_m_n m_n;
         int pipe = intel_crtc->pipe;
         enum transcoder cpu_transcoder = intel_crtc->cpu_transcoder;
+        int target_clock;
 
         /*
          * Find the lane count in the intel_encoder private
@@ -835,13 +836,22 @@ intel_dp_set_m_n(struct drm_crtc *crtc, struct drm_display_mode *mode,
                 }
         }
 
+        target_clock = mode->clock;
+        for_each_encoder_on_crtc(dev, crtc, intel_encoder) {
+                if (intel_encoder->type == INTEL_OUTPUT_EDP) {
+                        target_clock = intel_edp_target_clock(intel_encoder,
+                                                              mode);
+                        break;
+                }
+        }
+
         /*
          * Compute the GMCH and Link ratios. The '3' here is
          * the number of bytes_per_pixel post-LUT, which we always
          * set up for 8-bits of R/G/B, or 3 bytes total.
          */
         intel_link_compute_m_n(intel_crtc->bpp, lane_count,
-                               mode->clock, adjusted_mode->clock, &m_n);
+                               target_clock, adjusted_mode->clock, &m_n);
 
         if (IS_HASWELL(dev)) {
                 I915_WRITE(PIPE_DATA_M1(cpu_transcoder),