[openwrt/openwrt] ramips: mt7621: reduce MMC clock to 48 MHz

[LEDE Commits]

dangole pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/04818d5857ae69350ad2e00dc57eade174f64422

commit 04818d5857ae69350ad2e00dc57eade174f64422
Author: Daniel Golle <daniel at makrotopia.org>
AuthorDate: Fri Jul 12 02:38:53 2024 +0100

    ramips: mt7621: reduce MMC clock to 48 MHz
    
    The switch to the upstream mmc-mtk driver caused problems with MT7621
    because of unstable too high clock frequency:
    [   49.643291] mmc0: error -88 whilst initialising SD card
    [   49.890047] mmc0: error -88 whilst initialising SD card
    [   50.142414] mmc0: error -88 whilst initialising SD card
    [   50.419218] mmc0: error -88 whilst initialising SD card
    ...
    
    Fix this by reducing the clock speed to 48 MHz instead of 50 MHz, which
    is also the value used in upstream Linux mt7621.dtsi.
    
    With that change applied SD cards work as expected on MT7621 devices
    also with the new driver.
    
    Signed-off-by: Daniel Golle <daniel at makrotopia.org>
---
 target/linux/ramips/dts/mt7621.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/linux/ramips/dts/mt7621.dtsi b/target/linux/ramips/dts/mt7621.dtsi
index 033ba95dd7..da992bada4 100644
--- a/target/linux/ramips/dts/mt7621.dtsi
+++ b/target/linux/ramips/dts/mt7621.dtsi
@@ -365,7 +365,7 @@
 		interrupt-parent = <&gic>;
 		interrupts = <GIC_SHARED 20 IRQ_TYPE_LEVEL_HIGH>;
 
-		max-frequency = <50000000>;
+		max-frequency = <48000000>;
 
 		pinctrl-names = "default", "state_uhs";
 		pinctrl-0 = <&sdhci_pins>;