drm: Add support for alternate clocks of 4k modes

v2: Fix hmdi typo (Simon Farnsworth, Ville Syrjälä)

Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Simon Farnsworth <simon.farnsworth@onelan.co.uk>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dave Airlie <airlied@gmail.com>

1 files changed, 62 insertions, 6 deletions

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 9de573cd3683..2381abd452f1 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2409,6 +2409,54 @@ u8 drm_match_cea_mode(const struct drm_display_mode *to_match)
 }
 EXPORT_SYMBOL(drm_match_cea_mode);
 
+/*
+ * Calculate the alternate clock for HDMI modes (those from the HDMI vendor
+ * specific block).
+ *
+ * It's almost like cea_mode_alternate_clock(), we just need to add an
+ * exception for the VIC 4 mode (4096x2160@24Hz): no alternate clock for this
+ * one.
+ */
+static unsigned int
+hdmi_mode_alternate_clock(const struct drm_display_mode *hdmi_mode)
+{
+        if (hdmi_mode->vdisplay == 4096 && hdmi_mode->hdisplay == 2160)
+                return hdmi_mode->clock;
+
+        return cea_mode_alternate_clock(hdmi_mode);
+}
+
+/*
+ * drm_match_hdmi_mode - look for a HDMI mode matching given mode
+ * @to_match: display mode
+ *
+ * An HDMI mode is one defined in the HDMI vendor specific block.
+ *
+ * Returns the HDMI Video ID (VIC) of the mode or 0 if it isn't one.
+ */
+static u8 drm_match_hdmi_mode(const struct drm_display_mode *to_match)
+{
+        u8 mode;
+
+        if (!to_match->clock)
+                return 0;
+
+        for (mode = 0; mode < ARRAY_SIZE(edid_4k_modes); mode++) {
+                const struct drm_display_mode *hdmi_mode = &edid_4k_modes[mode];
+                unsigned int clock1, clock2;
+
+                /* Make sure to also match alternate clocks */
+                clock1 = hdmi_mode->clock;
+                clock2 = hdmi_mode_alternate_clock(hdmi_mode);
+
+                if ((KHZ2PICOS(to_match->clock) == KHZ2PICOS(clock1) ||
+                     KHZ2PICOS(to_match->clock) == KHZ2PICOS(clock2)) &&
+                    drm_mode_equal_no_clocks(to_match, hdmi_mode))
+                        return mode + 1;
+        }
+        return 0;
+}
+
 static int
 add_alternate_cea_modes(struct drm_connector *connector, struct edid *edid)
 {
@@ -2426,18 +2474,26 @@ add_alternate_cea_modes(struct drm_connector *connector, struct edid *edid)
          * with the alternate clock for certain CEA modes.
          */
         list_for_each_entry(mode, &connector->probed_modes, head) {
-                const struct drm_display_mode *cea_mode;
+                const struct drm_display_mode *cea_mode = NULL;
                 struct drm_display_mode *newmode;
-                u8 cea_mode_idx = drm_match_cea_mode(mode) - 1;
+                u8 mode_idx = drm_match_cea_mode(mode) - 1;
                 unsigned int clock1, clock2;
 
-                if (cea_mode_idx >= ARRAY_SIZE(edid_cea_modes))
-                        continue;
+                if (mode_idx < ARRAY_SIZE(edid_cea_modes)) {
+                        cea_mode = &edid_cea_modes[mode_idx];
+                        clock2 = cea_mode_alternate_clock(cea_mode);
+                } else {
+                        mode_idx = drm_match_hdmi_mode(mode) - 1;
+                        if (mode_idx < ARRAY_SIZE(edid_4k_modes)) {
+                                cea_mode = &edid_4k_modes[mode_idx];
+                                clock2 = hdmi_mode_alternate_clock(cea_mode);
+                        }
+                }
 
-                cea_mode = &edid_cea_modes[cea_mode_idx];
+                if (!cea_mode)
+                        continue;
 
                 clock1 = cea_mode->clock;
-                clock2 = cea_mode_alternate_clock(cea_mode);
 
                 if (clock1 == clock2)
                         continue;