Re: [PATCH V2 20/26] imx: dynamic setting mmcdev and mmcroot

[Tim Harvey <tharvey@gateworks.com>]

On Tue, Apr 5, 2022 at 10:56 PM Peng Fan (OSS) <peng.fan@oss.nxp.com> wrote:
>
> From: Peng Fan <peng.fan@nxp.com>
>
> Dynamic setting mmcdev and mmcroot.
> Then when boot linux, we can have correct "root=/dev/mmcblk[x]p2"
>
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
>  arch/arm/include/asm/mach-imx/sys_proto.h |  2 +
>  board/freescale/common/Makefile           |  3 ++
>  board/freescale/common/mmc.c              | 49 +++++++++++++++++++++++
>  3 files changed, 54 insertions(+)
>  create mode 100644 board/freescale/common/mmc.c
>
> diff --git a/arch/arm/include/asm/mach-imx/sys_proto.h b/arch/arm/include/asm/mach-imx/sys_proto.h
> index 0c0c7814fb2..37fd427cc00 100644
> --- a/arch/arm/include/asm/mach-imx/sys_proto.h
> +++ b/arch/arm/include/asm/mach-imx/sys_proto.h
> @@ -228,6 +228,8 @@ int mxs_reset_block(struct mxs_register_32 *reg);
>  int mxs_wait_mask_set(struct mxs_register_32 *reg, u32 mask, u32 timeout);
>  int mxs_wait_mask_clr(struct mxs_register_32 *reg, u32 mask, u32 timeout);
>
> +void board_late_mmc_env_init(void);
> +
>  unsigned long call_imx_sip(unsigned long id, unsigned long reg0,
>                            unsigned long reg1, unsigned long reg2,
>                            unsigned long reg3);
> diff --git a/board/freescale/common/Makefile b/board/freescale/common/Makefile
> index f13965daf2e..4df484935f4 100644
> --- a/board/freescale/common/Makefile
> +++ b/board/freescale/common/Makefile
> @@ -63,6 +63,9 @@ obj-$(CONFIG_ZM7300)          += zm7300.o
>  obj-$(CONFIG_POWER_PFUZE100)   += pfuze.o
>  obj-$(CONFIG_DM_PMIC_PFUZE100) += pfuze.o
>  obj-$(CONFIG_POWER_MC34VR500)  += mc34vr500.o
> +ifneq (,$(filter $(SOC), imx8ulp))
> +obj-y                          += mmc.o
> +endif
>
>  obj-$(CONFIG_LS102XA_STREAM_ID)        += ls102xa_stream_id.o
>
> diff --git a/board/freescale/common/mmc.c b/board/freescale/common/mmc.c
> new file mode 100644
> index 00000000000..8cd5079f962
> --- /dev/null
> +++ b/board/freescale/common/mmc.c
> @@ -0,0 +1,49 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright 2016 Freescale Semiconductor, Inc.
> + * Copyright 2018-2022 NXP
> + */
> +
> +#include <common.h>
> +#include <command.h>
> +#include <asm/arch/sys_proto.h>
> +#include <linux/errno.h>
> +#include <asm/io.h>
> +#include <stdbool.h>
> +#include <mmc.h>
> +#include <env.h>
> +
> +static int check_mmc_autodetect(void)
> +{
> +       char *autodetect_str = env_get("mmcautodetect");
> +
> +       if (autodetect_str && !strcmp(autodetect_str, "yes"))
> +               return 1;
> +
> +       return 0;
> +}
> +
> +/* This should be defined for each board */
> +__weak int mmc_map_to_kernel_blk(int dev_no)
> +{
> +       return dev_no;
> +}
> +
> +void board_late_mmc_env_init(void)
> +{
> +       char cmd[32];
> +       char mmcblk[32];
> +       u32 dev_no = mmc_get_env_dev();
> +
> +       if (!check_mmc_autodetect())
> +               return;
> +
> +       env_set_ulong("mmcdev", dev_no);
> +
> +       /* Set mmcblk env */
> +       sprintf(mmcblk, "/dev/mmcblk%dp2 rootwait rw", mmc_map_to_kernel_blk(dev_no));
> +       env_set("mmcroot", mmcblk);
> +
> +       sprintf(cmd, "mmc dev %d", dev_no);
> +       run_command(cmd, 0);
> +}
> --
> 2.35.1
>

Peng,

I see Stefano already applied this but I'm not sure I agree with it.
Why should you assume that U-Boot and Linux have the same device
mapping? The kernel device mapping is not guaranteed to be consistent.
Every time I have asked about this I've been told the standard was to
use a boot script that used 'part' to determine the UUID of the boot
device from U-Boot's perspective then use root=PARTUUID= to match that
from the kernel's perspective.

For example if using CONFIG_DISTRO_DEFAULTS=y (which I think everyone
should be using) your bootscript would look like this:
part uuid ${devtype} ${devnum}:${distro_bootpart} uuid
setenv bootargs "root=PARTUUID=${uuid} rootwait $bootargs"

Best Regards,

Tim