[U-Boot] [PATCH] imx: Introduce CONFIG_SPL_FORCE_MMC_BOOT to force MMC boot on falcon mode

Lukasz Majewski
2019-09-04T09:54:40Z

Hi Stefano, Heiko,

> On 04/09/19 10:46, Lukasz Majewski wrote:
> > Hi Heiko,
> >
> >> Hello Lukasz,
> >>
> >> added Stefano to cc as he is the imx custodian.
> >
> > I've relied on patman ... Thanks for adding Stefano to CC.
> >
> >>
> >> Am 03.09.2019 um 23:43 schrieb Lukasz Majewski:
> >>> This change tries to fix the following problem:
> >>>
> >>> - The board boots (to be more precise - ROM loads SPL) from a slow
> >>> SPI-NOR memory.
> >>> As a result the spl_boot_device() will return SPI-NOR as a boot
> >>> device (which is correct).
> >>>
> >>> - The problem is that in 'falcon boot' the eMMC is used as a boot
> >>> medium to load kernel from its partition.
> >>> Calling spl_boot_device() will break things as it returns
> >>> SPI-NOR device.
> >>>
> >>> To fix this issue the new CONFIG_SPL_FORCE_MMC_BOOT Kconfig flag
> >>> is introduced to handle this special use case. By default it is
> >>> not defined, so there is no change in the legacy code flow.
> >>>
> >>> Signed-off-by: Lukasz Majewski <lukma@denx.de>
> >>>
> >>>
> >>> ---
> >>>
> >>> This patch is a follow up of previous discussion/fix:
> >>> https://patchwork.ozlabs.org/patch/796237/
> >>>
> >>> Travis-CI:
> >>> https://travis-ci.org/lmajewski/u-boot-dfu/builds/580272414
> >>> ---
> >>> arch/arm/mach-imx/spl.c | 11 +++++++++++
> >>> common/spl/Kconfig | 7 +++++++
> >>> 2 files changed, 18 insertions(+)
> >>
> >> I have just similiar change for an imx6ull based board ...
> >
> > Also one more of my boards uses this trick (i.MX28 based one).
> >
> >> just antoher usecase: In factory empty board boots into USB SDP
> >> mode, and SPL gets loaded with usb_loader ... SPL detects a sd
> >> card (there is no sd card slot mounted, mmc boot is disabled! They
> >> attach only one for installing software)
> >
> > So there is no dedicated SD card slot (also the mmc is disabled on
> > that point).
> > Instead, in the factory the sd card is attached to pads - just for
> > this time.
> >
> >> and boots U-Boot and system from sd card.
> >> Than all software gets installed fully automated with the help of
> >> swupdate ...
> >
> > Ok.
> >
> >>
> >>> diff --git a/arch/arm/mach-imx/spl.c b/arch/arm/mach-imx/spl.c
> >>> index 1f230aca3397..daa3d8f7ed94 100644
> >>> --- a/arch/arm/mach-imx/spl.c
> >>> +++ b/arch/arm/mach-imx/spl.c
> >>> @@ -178,7 +178,18 @@ int g_dnl_bind_fixup(struct
> >>> usb_device_descriptor *dev, const char *name) /* called from
> >>> spl_mmc to see type of boot mode for storage (RAW or FAT) */ u32
> >>> spl_boot_mode(const u32 boot_device) {
> >>> +/*
> >>> + * When CONFIG_SPL_FORCE_MMC_BOOT is defined the 'boot_device' is
> >>> used
> >>> + * unconditionally to decide about device to use for booting.
> >>> + * This is crucial for falcon boot mode, when board boots up
> >>> (i.e. ROM
> >>> + * loads SPL) from slow SPI-NOR memory and afterwards the SPL's
> >>> 'falcon' boot
> >>> + * mode is used to load Linux OS from eMMC partition.
> >>> + */
> >>> +#ifdef CONFIG_SPL_FORCE_MMC_BOOT
> >>> + switch (boot_device) {
> >>> +#else
> >>> switch (spl_boot_device()) {
> >>> +#endif
> >>
> >> Just dummy question .. couldn;t we switch to use always
> >> boot_device?
> >
> > Stefano has provided some rationale for the need of
> > spl_boot_device() in the previous version of this fix [1]:
> >
> > https://patchwork.ozlabs.org/patch/796237/
> >
> >
> >>
> >> In my case I had a board specific:
> >>
> >> void board_boot_order(u32 *spl_boot_list)
> >> {
> >> spl_boot_list[0] = BOOT_DEVICE_MMC1;
> >> spl_boot_list[1] = BOOT_DEVICE_SPI;
> >> spl_boot_list[2] = BOOT_DEVICE_BOARD;
> >> spl_boot_list[3] = BOOT_DEVICE_NONE;
> >> }
> >>
> >> which leads that BOOT_DEVICE_MMC1 is passed to spl_boot_mode()
> >
> > Is your board normally booting from MMC or SPI-NOR (from where SoC
> > ROM loads SPL) ?
> >
> >>
> >> If MMC1 is not found, it tries to boot U-Boot from SPI, and if
> >> this is empty, as fallback board go into USB SDP mode.
> >>
> >> The weak function of board_boot_order is:
> >>
> >> __weak void board_boot_order(u32 *spl_boot_list)
> >> {
> >> spl_boot_list[0] = spl_boot_device();
> >> }
> >>
> >> which is exactly what we pass to spl_boot_mode() ... so instead
> >> calling spl_boot_device() twice we can use the passed boot_device
> >> ... and save the ifdef and new Kconfig option.
> >>
> >> But may I oversee something ?
> >
> > Please read the Stefano's reply from [1] - the spl_boot_device()
> > has a valid use cases as well.
>
> Nevertheless, why do we need to add a new compiler switch if this can
> be check into board code ? You just need that spl_boot_device()
> returns the device you want (MMC for falcon boot).

Current status:

git grep -n "spl_boot_mode" | grep weak
common/spl/spl_mmc.c:287:u32 __weak spl_boot_mode(const u32 boot_device)

git grep -n "board_boot_order" | grep weak
common/spl/spl.c:491:__weak void board_boot_order(u32 *spl_boot_list)

The spl_boot_device() is defined in arch/arm/mach-imx/spl.c [*] as a NON
__weak function:
git grep -n "spl_boot_device" | grep weak

Shall I make this function [*] as __weak and provide override for it
in the board file?

The problem is in the call of spl_boot_mode() (which is overridden
already in arch/arm/mach-imx/spl.c) at common/spl/spl_mmc.c

Which then calls spl_boot_device() [**], which may return (correctly)
SPI-NOR for eMMC.

As is now spl_boot_device() is not a __weak function.

> Why do you need to
> force it in this way ?

The option is to use the proposed patch to make spl_boot_device as a
weak function.

>
> Regards,
> Stefano
>
> >
> >>
> >>> /* for MMC return either RAW or FAT mode */
> >>> case BOOT_DEVICE_MMC1:
> >>> case BOOT_DEVICE_MMC2:
> >>> diff --git a/common/spl/Kconfig b/common/spl/Kconfig
> >>> index f467eca2be72..3460beb62d59 100644
> >>> --- a/common/spl/Kconfig
> >>> +++ b/common/spl/Kconfig
> >>> @@ -607,6 +607,13 @@ config SPL_MMC_SUPPORT
> >>> this option to build the drivers in drivers/mmc as
> >>> part of an SPL build.
> >>>
> >>> +config SPL_FORCE_MMC_BOOT
> >>> + bool "Force SPL's falcon boot from MMC"
> >>> + depends on SPL_MMC_SUPPORT
> >>> + default n
> >>> + help
> >>> + Force SPL's falcon boot to use MMC device for Linux
> >>> kernel booting.
> >>
> >> Hmm... falcon boot is just one use case. I would drop "falcon boot"
> >> It just to force boot from MMC.
> >
> > Ok. I will rewrite the help message.
> >
> >>
> >>> +
> >>> config SPL_MMC_TINY
> >>> bool "Tiny MMC framework in SPL"
> >>> depends on SPL_MMC_SUPPORT
> >>>
> >>
> >> bye,
> >> Heiko
> >
> >
> >
> > Best regards,
> >
> > Lukasz Majewski
> >
> > --
> >
> > DENX Software Engineering GmbH, Managing Director: Wolfgang
> > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
> > Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> > lukma at denx.de
>
>

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma at denx.de
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