[EXT] Re: [PATCH v2 2/2] imx: Support i.MX91 11x11 FRDM board

[Joseph Guo (OSS)]

On 12/4/2025 10:03 PM, Fabio Estevam wrote:
> Hi Joseph,
> 
> On Thu, Dec 4, 2025 at 4:12 AM Joseph Guo (OSS) <qijian.guo at oss.nxp.com> wrote:
> 
>> Hi Fabio,
>>
>> USDHC2 is for SD card and its initial stage is at u-boot.
>> The IO voltage switch from 3.3v to 1.8v need extra 8ms time on some
>> platform. I also tested without this delay, SD card can work as SD3.0 on
>> imx91 frdm platform.
>>
>> I prefer to remain this to avoid potential risk as 91evk 93evk 93frdm
>> all remain this property.
> 
> I understand that a few NXP boards use this
> fsl,signal-voltage-switch-extra-delay-ms property.
> 
> Linux does not use it. U-Boot should not use it either. Whatever
> solution the kernel applies to provide this delay, let's use it in
> U-Boot.
> 
> I would really appreciate it if you could investigate this with the
> NXP folks and try to remove this custom property from U-Boot.
> 
> Let's keep the U-Bot dts files as close as possible with Linux.
> 
> I appreciate your understanding and cooperation.
> 
> Thanks

Hi Fabio,

I understand your requirement. But as I said, the IO voltage switch only 
happen on u-boot stage, so it is kind of u-boot specific requirement.
So you mean we need to add this delay control into kernel driver, and 
add this property into kernel dts even kernel stage didn't need to 
control it?

Since we don't have this issue on FRDM-IMX91. How about I remove this 
property on this commit first. And we can have further discussion on how 
to resolve this property.

Regards,
Joseph