@@ -1923,6 +1923,14 @@ int intel_crtc_compute_min_cdclk(const struct intel_crtc_state *crtc_state)
if (crtc_state->has_audio && INTEL_GEN(dev_priv) >= 9)
min_cdclk = max(2 * 96000, min_cdclk);
+ /*
+ * On Valleyview the GOP always uses 320000/333333 KHz if DSI is used,
+ * using a lower clock causes causes sync issues with some panels.
+ */
+ if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DSI) &&
+ IS_VALLEYVIEW(dev_priv))
+ min_cdclk = max(320000, min_cdclk);
+
if (min_cdclk > dev_priv->max_cdclk_freq) {
DRM_DEBUG_KMS("required cdclk (%d kHz) exceeds max (%d kHz)\n",
min_cdclk, dev_priv->max_cdclk_freq);
At least on the Chuwi Vi8 (non pro/plus) the LCD panel will show an image shifted aprox. 20% to the left (with wraparound) and sometimes also wrong colors, showing that the panel controller is starting with sampling the datastream somewhere mid-line. This happens after the first blanking and re-init of the panel. After looking at drm.debug output I noticed that initially we inherit the cdclk of 333333 KHz set by the GOP, but after the re-init we picked 266667 KHz, which turns out to be the cause of this problem, a quick hack to hard code the cdclk to 333333 KHz makes the problem go away. I've tested this on various Bay Trail devices: -Chuwi Vi8: 800x1280, 333333 at boot, requires 333333 to work properly -GP-electronic T701: 1024x600, 333333 at boot, works fine with 333333 -PEAQ C1010: 1920x1200, 333333 at boot, works fine with 333333 -PoV mobii-wintab-800w: 800x1280, 333333 at boot, works fine with 333333 -Asus Transformer-T100TA: 1368x768, 320000 at boot, works fine with 320000 So it seems that the GOP is always using what vlv_calc_cdclk calls freq_320 as cdclk clock. Also note the comment in vlv_calc_cdclk about it avoiding 200 Mhz as clock because that causes issues in some cases. This commit extends the "do not use 200 Mhz" workaround with an extra check to require atleast 320000 KHz (avoiding 266667 KHz) when a DSI panel is active. Signed-off-by: Hans de Goede <hdegoede@redhat.com> --- drivers/gpu/drm/i915/intel_cdclk.c | 8 ++++++++ 1 file changed, 8 insertions(+)