[PATCH 07/20] drm/sun4i: rgb: Validate the clock rate

[Maxime Ripard]

Our pixel clock cannot reach a high enough rate for some rather high while
common resolutions (like 1080p60).

Make sure we filter the resolutions we cannot reach in our mode_valid
function.

Fixes: 29e57fab97fc ("drm: sun4i: Add RGB output")
Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
---
 drivers/gpu/drm/sun4i/sun4i_rgb.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun4i_rgb.c 
b/drivers/gpu/drm/sun4i/sun4i_rgb.c
index ab6494818050..923f55039cb1 100644
--- a/drivers/gpu/drm/sun4i/sun4i_rgb.c
+++ b/drivers/gpu/drm/sun4i/sun4i_rgb.c
@@ -54,8 +54,13 @@ static int sun4i_rgb_get_modes(struct drm_connector 
*connector)
 static int sun4i_rgb_mode_valid(struct drm_connector *connector,
                                struct drm_display_mode *mode)
 {
+       struct sun4i_rgb *rgb = drm_connector_to_sun4i_rgb(connector);
+       struct sun4i_drv *drv = rgb->drv;
+       struct sun4i_tcon *tcon = drv->tcon;
        u32 hsync = mode->hsync_end - mode->hsync_start;
        u32 vsync = mode->vsync_end - mode->vsync_start;
+       unsigned long rate = mode->crtc_clock * 1000;
+       long rounded_rate;

        DRM_DEBUG_DRIVER("Validating modes...\n");

@@ -87,6 +92,15 @@ static int sun4i_rgb_mode_valid(struct drm_connector 
*connector,

        DRM_DEBUG_DRIVER("Vertical parameters OK\n");

+       rounded_rate = clk_round_rate(tcon->dclk, rate);
+       if (rounded_rate < rate)
+               return MODE_CLOCK_LOW;
+
+       if (rounded_rate > rate)
+               return MODE_CLOCK_HIGH;
+
+       DRM_DEBUG_DRIVER("Clock rate OK\n");
+
        return MODE_OK;
 }

-- 
2.8.2