[Linux-stm32] [PATCH v2 4/5] arm64: dts: st: use sdmmc2 pins_a on stm32mp257f-dk

[Mateusz Nowicki]

The eMMC of the STM32MP257F-DK was moved to the faster sdmmc2 pins_b
groups because HS200 at 100 MHz returned corrupted data with pins_a. The
cause was the delay block, which was used at 100 MHz, not the slew rate
of the pins. With "mmc: mmci: stm32: use the delay block above 100 MHz
on stm32mp25 SoC" HS200 works with pins_a at 100 MHz, and at 150 MHz
with the delay block.

Use pins_a again. Their slower outputs avoid overshoots on the SDMMC2
clock, which can disturb other blocks such as USB.

Fixes: 94911ce62b45 ("arm64: dts: st: enable eMMC on stm32mp257f-dk")
Suggested-by: Christophe Kerello <christophe.kerello at foss.st.com>
Signed-off-by: Mateusz Nowicki <mateusz.nowicki at posteo.net>
---

Notes:
    This needs patch 3 of the series: without it HS200 at 100 MHz loses writes
    with pins_a. With it, the eMMC of the DK passed every 832 MiB write and
    read-back run on pins_a at 100 MHz and at 150 MHz (see the cover letter).

 arch/arm64/boot/dts/st/stm32mp257f-dk.dts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/boot/dts/st/stm32mp257f-dk.dts b/arch/arm64/boot/dts/st/stm32mp257f-dk.dts
index a8f18508db3e..3776bf915160 100644
--- a/arch/arm64/boot/dts/st/stm32mp257f-dk.dts
+++ b/arch/arm64/boot/dts/st/stm32mp257f-dk.dts
@@ -357,8 +357,8 @@ &sdmmc1 {
 
 &sdmmc2 {
 	pinctrl-names = "default", "opendrain", "sleep";
-	pinctrl-0 = <&sdmmc2_b4_pins_b &sdmmc2_d47_pins_b>;
-	pinctrl-1 = <&sdmmc2_b4_od_pins_b &sdmmc2_d47_pins_b>;
+	pinctrl-0 = <&sdmmc2_b4_pins_a &sdmmc2_d47_pins_a>;
+	pinctrl-1 = <&sdmmc2_b4_od_pins_a &sdmmc2_d47_pins_a>;
 	pinctrl-2 = <&sdmmc2_b4_sleep_pins_a &sdmmc2_d47_sleep_pins_a>;
 	non-removable;
 	no-sd;
-- 
2.56.0