drm/i915: adjusted_mode->clock in the dp mode_fixup

... instead of changing mode->clock, which we should leave as-is.

After the previous patch we only touch that if it's a panel, and then
adjusted mode->clock equals adjusted_mode->clock. Outside of
intel_dp.c we only use ajusted_mode->clock in the mode_set functions.

Within intel_dp.c we only use it to calculate the dp dithering
and link bw parameters, so that's the only thing we need to fix
up.

As a temporary ugliness (until the cleanup in the next patch) we
pass the adjusted_mode into dp_dither for both parameters (because
that one still looks at mode->clock).

Note that we do overwrite adjusted_mode->clock with the selected dp
link clock, but that only happens after we've calculated everything we
need based on the dotclock of the adjusted output configuration.

Outside of intel_dp.c only intel_display.c uses adjusted_mode->clock,
and that stays the same after this patch (still equals the selected dp
link clock). intel_display.c also needs the actual dotclock (as
target_clock), but that has been fixed up in the previous patch.

v2: Adjust the debug message to also use adjusted_mode->clock.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -710,11 +710,6 @@ intel_dp_mode_fixup(struct drm_encoder *encoder, struct drm_display_mode *mode,
 		intel_fixed_panel_mode(intel_dp->panel_fixed_mode, adjusted_mode);
 		intel_pch_panel_fitting(dev, DRM_MODE_SCALE_FULLSCREEN,
 					mode, adjusted_mode);
-		/*
-		 * the mode->clock is used to calculate the Data&Link M/N
-		 * of the pipe. For the eDP the fixed clock should be used.
-		 */
-		mode->clock = intel_dp->panel_fixed_mode->clock;
 	}
 
 	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
@@ -722,13 +717,13 @@ intel_dp_mode_fixup(struct drm_encoder *encoder, struct drm_display_mode *mode,
 
 	DRM_DEBUG_KMS("DP link computation with max lane count %i "
 		      "max bw %02x pixel clock %iKHz\n",
-		      max_lane_count, bws[max_clock], mode->clock);
+		      max_lane_count, bws[max_clock], adjusted_mode->clock);
 
-	if (!intel_dp_adjust_dithering(intel_dp, mode, adjusted_mode))
+	if (!intel_dp_adjust_dithering(intel_dp, adjusted_mode, adjusted_mode))
 		return false;
 
 	bpp = adjusted_mode->private_flags & INTEL_MODE_DP_FORCE_6BPC ? 18 : 24;
-	mode_rate = intel_dp_link_required(mode->clock, bpp);
+	mode_rate = intel_dp_link_required(adjusted_mode->clock, bpp);
 
 	for (lane_count = 1; lane_count <= max_lane_count; lane_count <<= 1) {
 		for (clock = 0; clock <= max_clock; clock++) {