[PATCH v3 13/13] arm64: dts: st: add loopback clocks on LTDC node

[Raphael Gallais-Pou]

ck_ker_ltdc has the CLK_SET_RATE_PARENT flag.  While having this flag is
semantically correct, it for now leads to an improper setting of the
clock rate.  The ck_ker_ltdc parent clock is the flexgen 27, which does
not support changing rates yet.  To overcome this issue, a fixed clock
can be used for the kernel clock.

Add the clocks needed for the LTDC to work.

Signed-off-by: Raphael Gallais-Pou <raphael.gallais-...@foss.st.com>
---
 arch/arm64/boot/dts/st/stm32mp251.dtsi | 6 ++++++
 arch/arm64/boot/dts/st/stm32mp255.dtsi | 5 +++++
 2 files changed, 11 insertions(+)

diff --git a/arch/arm64/boot/dts/st/stm32mp251.dtsi 
b/arch/arm64/boot/dts/st/stm32mp251.dtsi
index 
6d9c0a430a8cc82542029f18b8a1a954a7c4fddb..24823bbfee31f15e813573ad1a0c4f67a125ce51
 100644
--- a/arch/arm64/boot/dts/st/stm32mp251.dtsi
+++ b/arch/arm64/boot/dts/st/stm32mp251.dtsi
@@ -52,6 +52,12 @@ clk_rcbsec: clk-rcbsec {
                        compatible = "fixed-clock";
                        clock-frequency = <64000000>;
                };
+
+               clk_flexgen_27_fixed: clk-54000000 {
+                       #clock-cells = <0>;
+                       compatible = "fixed-clock";
+                       clock-frequency = <54000000>;
+               };
        };
 
        firmware {
diff --git a/arch/arm64/boot/dts/st/stm32mp255.dtsi 
b/arch/arm64/boot/dts/st/stm32mp255.dtsi
index 
a3b5ae25d28c83ade12c2ff69b82c9cccfd29b00..07c200470b2cedde771ae987f2267d6097ea78f0
 100644
--- a/arch/arm64/boot/dts/st/stm32mp255.dtsi
+++ b/arch/arm64/boot/dts/st/stm32mp255.dtsi
@@ -5,6 +5,11 @@
  */
 #include "stm32mp253.dtsi"
 
+&ltdc {
+       clocks = <&clk_flexgen_27_fixed>, <&rcc CK_BUS_LTDC>, <&syscfg>, 
<&lvds>;
+       clock-names = "lcd", "bus", "ref", "lvds";
+};
+
 &rifsc {
        lvds: lvds@48060000 {
                compatible = "st,stm32mp255-lvds", "st,stm32mp25-lvds";

-- 
2.25.1