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

[Peng Fan (OSS)]

> Subject: Re: [PATCH V2 20/26] imx: dynamic setting mmcdev and mmcroot
> 
> On Tue, Apr 5, 2022 at 10:56 PM Peng Fan (OSS) <peng.fan at oss.nxp.com>
> wrote:
> >
> > From: Peng Fan <peng.fan at 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 at 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"

For NXP internal release, we still use legacy way, with cmd in config header file,
let me check and update to fix this. Thanks for pointing out.

Thanks,
Peng.

> 
> Best Regards,
> 
> Tim