Can't access mmc #0 on mt7623 when booted from external SD

[David Woodhouse]

On Tue, 2020-06-16 at 18:21 +0200, Michael Nazzareno Trimarchi wrote:
> Hi David
> 
> On Tue, Jun 16, 2020 at 6:16 PM David Woodhouse <dwmw2 at infradead.org> wrote:
> > 
> > The Banana Pi R2 bootloader will load U-Boot from either the internal
> > eMMC, or the external SD card if the latter is present.
> > 
> > If booted from the eMMC (and an SD card is subsequently inserted), both
> > work from U-Boot. Both also work from Linux, whichever device is booted
> > from.
> > 
> > If booted from SD, the internal eMMC cannot be accessed from U-Boot.
> > This makes it slightly difficult for me to write a U-Boot script which
> > installs OpenWRT from the SD card to the internal eMMC...
> 
> I'm thinking that bootrom do the right job for you when both are working.

Yes. It does seem likely that when loading U-Boot from the eMMC, the
preloader is initialising it for us. But when the preloader loads
U-Boot from the SD card, it possibly doesn't initialise the eMMC
controller at all.

The Linux driver does cope with this, and drives the internal eMMC.
Perhaps there's just some init code missing from the U-Boot mtk-sd
driver?



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