drm/i915: don't clobber the special upscaling lvds timings

This regression has been introduced in

commit ca9bfa7eed20ea34e862804e62aae10eb159edbb
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Sat Jan 28 14:49:20 2012 +0100

    drm/i915: fixup interlaced vertical timings confusion, part 1

Unfortunately that commit failed to take into account that the lvds
code does some special adjustements to the crtc timings for upscaling
an centering.

Fix this by explicitly computing crtc timings in the lvds mode fixup
function and setting a special flag in mode->private_flags if the crtc
timings have been adjusted.

v2: Add a comment to explain the new mode driver private flag,
suggested by Eugeni Dodonov.

v3: Kill the confusing and now redundant set_crtcinfo call in
intel_fixed_panel_mode, noticed by Chris Wilson.

Reported-and-Tested-by: Hans de Bruin <jmdebruin@xmsnet.nl>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=43071
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -3478,8 +3478,11 @@ static bool intel_crtc_mode_fixup(struct drm_crtc *crtc,
 			return false;
 	}
 
-	/* All interlaced capable intel hw wants timings in frames. */
-	drm_mode_set_crtcinfo(adjusted_mode, 0);
+	/* All interlaced capable intel hw wants timings in frames. Note though
+	 * that intel_lvds_mode_fixup does some funny tricks with the crtc
+	 * timings, so we need to be careful not to clobber these.*/
+	if (!(adjusted_mode->private_flags & INTEL_MODE_CRTC_TIMINGS_SET))
+		drm_mode_set_crtcinfo(adjusted_mode, 0);
 
 	return true;
 }

drivers/gpu/drm/i915/intel_drv.h

@@ -105,6 +105,10 @@
 #define INTEL_MODE_PIXEL_MULTIPLIER_SHIFT (0x0)
 #define INTEL_MODE_PIXEL_MULTIPLIER_MASK (0xf << INTEL_MODE_PIXEL_MULTIPLIER_SHIFT)
 #define INTEL_MODE_DP_FORCE_6BPC (0x10)
+/* This flag must be set by the encoder's mode_fixup if it changes the crtc
+ * timings in the mode to prevent the crtc fixup from overwriting them.
+ * Currently only lvds needs that. */
+#define INTEL_MODE_CRTC_TIMINGS_SET (0x20)
 
 static inline void
 intel_mode_set_pixel_multiplier(struct drm_display_mode *mode,

drivers/gpu/drm/i915/intel_lvds.c

@@ -187,6 +187,8 @@ centre_horizontally(struct drm_display_mode *mode,
 
 	mode->crtc_hsync_start = mode->crtc_hblank_start + sync_pos;
 	mode->crtc_hsync_end = mode->crtc_hsync_start + sync_width;
+
+	mode->private_flags |= INTEL_MODE_CRTC_TIMINGS_SET;
 }
 
 static void
@@ -208,6 +210,8 @@ centre_vertically(struct drm_display_mode *mode,
 
 	mode->crtc_vsync_start = mode->crtc_vblank_start + sync_pos;
 	mode->crtc_vsync_end = mode->crtc_vsync_start + sync_width;
+
+	mode->private_flags |= INTEL_MODE_CRTC_TIMINGS_SET;
 }
 
 static inline u32 panel_fitter_scaling(u32 source, u32 target)
@@ -283,6 +287,8 @@ static bool intel_lvds_mode_fixup(struct drm_encoder *encoder,
 	for_each_pipe(pipe)
 		I915_WRITE(BCLRPAT(pipe), 0);
 
+	drm_mode_set_crtcinfo(adjusted_mode, 0);
+
 	switch (intel_lvds->fitting_mode) {
 	case DRM_MODE_SCALE_CENTER:
 		/*

drivers/gpu/drm/i915/intel_panel.c

@@ -47,8 +47,6 @@ intel_fixed_panel_mode(struct drm_display_mode *fixed_mode,
 	adjusted_mode->vtotal = fixed_mode->vtotal;
 
 	adjusted_mode->clock = fixed_mode->clock;
-
-	drm_mode_set_crtcinfo(adjusted_mode, 0);
 }
 
 /* adjusted_mode has been preset to be the panel's fixed mode */