Re: [PATCH v3 2/2] imx8mn/8mp: Allow booting via USB

Tim Harvey
2022-04-25T23:16:04Z

On Mon, Apr 25, 2022 at 3:47 PM Fabio Estevam <festevam@denx.de> wrote:
>
> Hi Tim,
>
> On 25/04/2022 16:41, Tim Harvey wrote:
>
> > Fabio,
> >
> > Thanks - this at least allows me to boot on imx8mp-venice-gw74xx
> > without needing to enable CONFIG_ENV_IS_NOWHERE.
>
> Care to reply with your Tested-by?

Sure,

Tested-By: Tim Harvey <tharvey@gateworks.com>

>
> >
> > I do however notice when I do so env is attempted to load from MMC dev
> > 0 (CONFIG_ENV_IS_IN_MMC=y) - what controls the device number in this
> > case as for this board, the emmc is dev 2.
>
> That's a separate issue.

agreed it would be a separate issue... just curious if you knew where
that was coming from. It certainly isn't a common behavior to boot via
USB then expect 'saveenv' to save to a specific eMMC device.

>
> I see that you replied to Peng's patch:
> "imx: dynamic setting mmcdev and mmcroot" and this is likely the cause
> for your env numbering problem.

That has nothing to do with the mmc device used for U-Boot env. Commit
f342c9e381c0 ("imx: dynamic setting mmcdev and mmcroot") adds setting
'mmcroot=' if mmcautodetect=yes which seems to me like a completely
inappropriate hack that assumes U-Boot's mmc device numbering matches
the kernels device numbering (which has changed over time and is not a
stable ABI). I believe you have been involved in discussions about
that in the past as well regarding how to best tell the kernel what
the root device is. Every discussion I have seen (and there have been
many over the years) end up with the recommendation of using UUID.

Best regards,

Tim