[PATCH] arm64: dts: amlogic: sm1-bananapi: lower SD card speed for stability

[Christian Hewitt]

Users report being able to boot (u-boot) from SD card but kernel
init then fails to mount partitions on the card containing boot
media resulting in first-boot failure. System logs show only the
probe of the mmc devices: the SD card is seen, but no partitions
are found so init fails to mount them and boot stalls.

Reducing the speed of the SD card from 50MHz to 35MHz results in
complete probing of the card and successful boot.

Signed-off-by: Christian Hewitt <christianshewitt at gmail.com>
---
The same workaround of dropping to 35MHz is also done with the
ac2xx dtsi; which has a comment about CRC errors being seen at
50MHz. It's probable this is the same although I forget now how
that diagnosis was done (or who did it, Martin perhaps?). I've
removed the FIXUP comment and added one about boot failures
being seen at 50Mhz but if you prefer to repeat the CRC comment
from ac2xx feel free to fixup when applying or I can send a v2
with that change. Links to original issue reports with user test
results [0] [1] are below:

[0] https://github.com/LibreELEC/LibreELEC.tv/issues/10027
[1] https://github.com/libretro/Lakka-LibreELEC/issues/2059

 arch/arm64/boot/dts/amlogic/meson-sm1-bananapi.dtsi | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/boot/dts/amlogic/meson-sm1-bananapi.dtsi b/arch/arm64/boot/dts/amlogic/meson-sm1-bananapi.dtsi
index 40db95f64636..03b4b414cd5f 100644
--- a/arch/arm64/boot/dts/amlogic/meson-sm1-bananapi.dtsi
+++ b/arch/arm64/boot/dts/amlogic/meson-sm1-bananapi.dtsi
@@ -384,11 +384,10 @@ &sd_emmc_b {
 
 	bus-width = <4>;
 	cap-sd-highspeed;
-	max-frequency = <50000000>;
+	/* Boot failures are observed at 50MHz */
+	max-frequency = <35000000>;
 	disable-wp;
 
-	/* TOFIX: SD card is barely usable in SDR modes */
-
 	cd-gpios = <&gpio GPIOC_6 GPIO_ACTIVE_LOW>;
 	vmmc-supply = <&tflash_vdd>;
 	vqmmc-supply = <&vddio_c>;
-- 
2.34.1