1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
index dda904ec0534..c12f9bd12904 100644
--- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
+++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
@@ -208,8 +208,27 @@ static int sun4i_hdmi_get_modes(struct drm_connector *connector)
         return ret;
 }
 
+static int sun4i_hdmi_mode_valid(struct drm_connector *connector,
+                                 struct drm_display_mode *mode)
+{
+        struct sun4i_hdmi *hdmi = drm_connector_to_sun4i_hdmi(connector);
+        long rate = mode->clock * 1000;
+        long diff = rate / 200; /* +-0.5% allowed by HDMI spec */
+        long rounded_rate;
+
+        /* 165 MHz is the typical max pixelclock frequency for HDMI <= 1.2 */
+        if (rate > 165000000)
+                return MODE_CLOCK_HIGH;
+        rounded_rate = clk_round_rate(hdmi->tmds_clk, rate);
+        if (max(rounded_rate, rate) - min(rounded_rate, rate) < diff &&
+            rounded_rate > 0)
+                return MODE_OK;
+        return MODE_NOCLOCK;
+}
+
 static const struct drm_connector_helper_funcs sun4i_hdmi_connector_helper_funcs = {
         .get_modes      = sun4i_hdmi_get_modes,
+        .mode_valid     = sun4i_hdmi_mode_valid,
 };
 
 static enum drm_connector_status