Re: [PATCH 1/8] spacemit: k1: select boot device via config registers

[Yao Zi <me@ziyao.cc>]

On Wed, Jun 24, 2026 at 08:46:40AM +0800, Eric Chung wrote:
> On Sat, Jun 13, 2026 at 11:51 AM 'Yao Zi' via uboot <uboot@riscstar.com> wrote:
> >
> > On Fri, Jun 12, 2026 at 04:18:54PM -0400, Raymond Mao wrote:
> > > From: Guodong Xu <guodong@riscstar.com>
> > >
> > > Add logic to determine the current boot device by reading the
> > > SoC's configuration registers, rather than using a hardcoded
> > > default.
> > >
> > > Signed-off-by: Guodong Xu <guodong@riscstar.com>
> > > Signed-off-by: Raymond Mao <raymond.mao@riscstar.com>
> > > ---
> > >  board/spacemit/k1/spl.c | 77 ++++++++++++++++++++++++++++++++++++++++-
> > >  1 file changed, 76 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/board/spacemit/k1/spl.c b/board/spacemit/k1/spl.c
> > > index 0db362130e4..d5e87d79fa2 100644
> > > --- a/board/spacemit/k1/spl.c
> > > +++ b/board/spacemit/k1/spl.c
> >
> > ...
> > > +             switch (sel) {
> > > +             case BOOT_STRAP_MODE_EMMC:
> > > +                     mode = BOOT_MODE_EMMC;
> > > +                     break;
> > > +             case BOOT_STRAP_MODE_NAND:
> > > +                     mode = BOOT_MODE_NAND;
> > > +                     break;
> > > +             case BOOT_STRAP_MODE_SPI:
> > > +                     mode = BOOT_MODE_SPI;
> > > +                     break;
> > > +             case BOOT_STRAP_MODE_SD:
> > > +             default:
> > > +                     mode = BOOT_MODE_SD;
> > > +                     break;
> > > +             }
> > > +     }
> > > +     /* TODO:
> > > +      *   The current upstream DTS file only contains the eMMC node. When
> > > +      *   the SD node is added via an overlay, the eMMC device ends up as
> > > +      *   MMC1 in SPL.
> >
> > Why not fix this with an extra alias in the overlay dt?
> >
> 
> That approach doesn't really help — with the alias, mmc0 and mmc1 get
> swapped, which ultimately breaks ABI consistency.

Sorry I didn't read you correctly, I'm not sure which you are trying to
keep consistency with.

I did a check in Linux next-20260623, and the aliases for bananapi-f3
look like,

        aliases {
		ethernet0 = &eth0;
		ethernet1 = &eth1;
		serial0 = &uart0;
		spi3 = &spi3;
		i2c2 = &i2c2;
		i2c8 = &i2c8;
		mmc0 = &emmc;
		mmc1 = &sdhci0;
	};

and for musepi-pro,

	aliases {
		ethernet0 = &eth0;
		serial0 = &uart0;
		i2c2 = &i2c2;
		i2c8 = &i2c8;
		mmc0 = &emmc;
		mmc1 = &sdhci0;
	};

So both of them assign emmc to mmc0 and sdhci0 (SD) to mmc1.

As a summary of the situation,

- Linux before SD card support is merged: emmc becomes mmc0 (without
  other hotpluggable devices present), no SD card
- Linux after SD card support is merged: emmc becomes mmc0, SD becomes
  mmc1

But PATCH 3 in the series assigns SD to mmc0 and emmc to MMC1, this
instead looks like an ABI breakage, and would go away as long as you
change the aliases? At the same time the comment here could be dropped.

> The hack on MMC1 only affects its role in SPL and doesn't impact the
> ABI in the devicetree. It's just a workaround. Eventually, both the
> overlay and the hack will be removed once the upstream DTS is robust
> enough.
> 
> 
> > > +      *   However, the SD device should be the first device (MMC1).
> > > +      *   This sequence needs to be corrected once the SD node is merged
> > > +      *   into the upstream U-Boot DTS file.
> > > +      */
> > > +     switch (mode) {
> > > +     case BOOT_MODE_EMMC:
> > > +             ret = BOOT_DEVICE_MMC1;
> > > +             break;
> > > +     case BOOT_MODE_NAND:
> > > +             ret = BOOT_DEVICE_NAND;
> > > +             break;
> > > +     case BOOT_MODE_SPI:
> > > +             ret = BOOT_DEVICE_SPI;
> > > +             break;
> > > +     case BOOT_MODE_USB:
> > > +             ret = BOOT_DEVICE_USB;
> > > +             break;
> > > +     case BOOT_MODE_SD:
> > > +             ret = BOOT_DEVICE_MMC2;
> > > +             break;
> > > +     default:
> > > +             ret = BOOT_DEVICE_MMC1;
> > > +             break;
> > > +     }
> > > +     return ret;
> > >  }
> > >
> > >  void spl_board_init(void)
> > > --
> > > 2.25.1
> > >
> >
> > Regards,
> > Yao Zi

Regards,
Yao Zi