[RFC PATCH 4/4] arm64: dts: st: select the Engicam RMM display pixel clock source

[Dario Binacchi]

On STM32MP255/257 the LTDC pixel clock is selected by the SYSCFG
pixel clock mux, whose reset value is the LVDS PHY pixel clock. With
the RGB panel the LTDC is then clocked by the unused LVDS PHY, and every
commit times out:

  [CRTC:42:crtc-0] vblank wait timed out
  [drm] *ERROR* flip_done timed out

Select the LTDC kernel clock as pixel clock source in the RGB panel
overlay and, for consistency, without relying on the reset value, the
LVDS PHY pixel clock in the LVDS panel overlay.

Signed-off-by: Dario Binacchi <dario.binacchi at amarulasolutions.com>

---

 ...57d-engicam-microgea-rmm-overlay-am-1280800w8tzqw-t00h.dtso | 3 +++
 ...2mp257d-engicam-microgea-rmm-overlay-rk050hr345-ct106a.dtso | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/arch/arm64/boot/dts/st/stm32mp257d-engicam-microgea-rmm-overlay-am-1280800w8tzqw-t00h.dtso b/arch/arm64/boot/dts/st/stm32mp257d-engicam-microgea-rmm-overlay-am-1280800w8tzqw-t00h.dtso
index 7655c1bf56b1..b44e1d3ddb1b 100644
--- a/arch/arm64/boot/dts/st/stm32mp257d-engicam-microgea-rmm-overlay-am-1280800w8tzqw-t00h.dtso
+++ b/arch/arm64/boot/dts/st/stm32mp257d-engicam-microgea-rmm-overlay-am-1280800w8tzqw-t00h.dtso
@@ -32,6 +32,9 @@ &framebuffer {
 };
 
 &ltdc {
+	/* LVDS output: the pixel clock is the LVDS PHY one */
+	assigned-clocks = <&syscfg>;
+	assigned-clock-parents = <&lvds>;
 	status = "okay";
 
 	port {
diff --git a/arch/arm64/boot/dts/st/stm32mp257d-engicam-microgea-rmm-overlay-rk050hr345-ct106a.dtso b/arch/arm64/boot/dts/st/stm32mp257d-engicam-microgea-rmm-overlay-rk050hr345-ct106a.dtso
index 7be955be58ed..7855086c33c7 100644
--- a/arch/arm64/boot/dts/st/stm32mp257d-engicam-microgea-rmm-overlay-rk050hr345-ct106a.dtso
+++ b/arch/arm64/boot/dts/st/stm32mp257d-engicam-microgea-rmm-overlay-rk050hr345-ct106a.dtso
@@ -38,6 +38,8 @@ touchscreen at 38 {
 &ltdc {
 	/* RGB output: the pixel clock is the LTDC kernel clock */
 	clocks = <&rcc CK_KER_LTDC>, <&rcc CK_BUS_LTDC>, <&syscfg>, <&lvds>;
+	assigned-clocks = <&syscfg>;
+	assigned-clock-parents = <&rcc CK_KER_LTDC>;
 	pinctrl-names = "default", "sleep";
 	pinctrl-0 = <&ltdc_pins_a>;
 	pinctrl-1 = <&ltdc_sleep_pins_a>;
-- 
2.43.0