Re: [PATCH] mmc: dts: am654: Add 650ms power off delay for proper MMC power cycle

[Judith Mendez <jm@ti.com>]

Hi Nishanth,

On 9/8/26 12:16, Nishanth Menon wrote:
> On 12:06-20260908, Judith Mendez wrote:
>> The AM65x EVM MMC1 VDD rail discharges slowly through RC circuit.
>> SD spec (section 6.4.1.3) requires VDD < 0.5V for minimum 1ms during
>> power cycle. Measured discharge time on this board is ~632.97ms to
>> reach < 0.5V threshold.
>>
>> During boot, MMC power cycles between boot stages. Without power off
>> delay, VDD doesn't fully discharge. Card retains 1.8V signaling state
>> from previous stages. When U-Boot initializes, card no longer asserts
>> S18A in ACMD41 response (already switched to 1.8V). Host misinterprets
>> card state and forces 1.8V anyway, falling into a bad state and causing
>> a boot failure.
>>
>> Add power-off-delay-us = 650000 (650ms) to ensure proper VDD discharge
>> during power cycles, allowing card to fully reset state between boot
>> stages.
>>
>> Signed-off-by: Judith Mendez <jm@ti.com>
> 
> Fixes ?

Fix is really for u-boot, don't think I can point to a u-boot
commit here can I?

~ Judith

> 
>> ---
>>   arch/arm64/boot/dts/ti/k3-am654-base-board.dts | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm64/boot/dts/ti/k3-am654-base-board.dts b/arch/arm64/boot/dts/ti/k3-am654-base-board.dts
>> index ca1300e130936..edcf039ccfbd0 100644
>> --- a/arch/arm64/boot/dts/ti/k3-am654-base-board.dts
>> +++ b/arch/arm64/boot/dts/ti/k3-am654-base-board.dts
>> @@ -460,6 +460,7 @@ &sdhci0 {
>>   &sdhci1 {
>>   	status = "okay";
>>   	vmmc-supply = <&vdd_mmc1_sd>;
>> +	power-off-delay-us = <650000>;
>>   	pinctrl-names = "default";
>>   	pinctrl-0 = <&main_mmc1_pins_default>;
>>   	ti,driver-strength-ohm = <50>;
>> -- 
>> 2.34.1
>>
>