[PATCH v1 1/3] mach-sunxi: Add boot device detection for SUNIV

[Andre Przywara]

On Wed,  9 Feb 2022 23:34:36 -0500
Jesse Taube <mr.bossman075 at gmail.com> wrote:

Hi Jesse,

many thanks for sending this, much appreciated!

> Use Samuel's suggestion of looking at the BootRom's stack
> to determine the boot device.

Can you please elaborate here what's going on, for future reference? Like:
=============
In contrast to other Allwinner SoCs the F1C100s BROM does not store a boot
source indicator in the eGON header in SRAM. This leaves us guessing where
we were exactly booted from, and for instance trying the SD card first,
even though we booted from SPI flash.
By inspecting the BROM code and by experimentation, Samuel found that the
top of the BROM stack contains unique pointers for each of the boot
sources, which we can use as a boot source indicator.

Remove the existing board_boot_order kludge and replace it with a proper
boot source indication function.
=============


> 
> Signed-off-by: Jesse Taube <Mr.Bossman075 at gmail.com>
> Suggested-by: Samuel Holland <samuel at sholland.org>
> ---
>  arch/arm/include/asm/arch-sunxi/spl.h | 15 ++++++++
>  arch/arm/mach-sunxi/board.c           | 50 ++++++++++++---------------
>  2 files changed, 38 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/arm/include/asm/arch-sunxi/spl.h b/arch/arm/include/asm/arch-sunxi/spl.h
> index 58cdf806d9..d069091297 100644
> --- a/arch/arm/include/asm/arch-sunxi/spl.h
> +++ b/arch/arm/include/asm/arch-sunxi/spl.h
> @@ -19,8 +19,23 @@
>  #define SUNXI_BOOTED_FROM_MMC0_HIGH	0x10
>  #define SUNXI_BOOTED_FROM_MMC2_HIGH	0x12
>  
> +/*
> + * Values taken from the Bootrom's stack used
> + * to determine where we booted from.
> + * 0xffff40f8: mmc0
> + * 0xffff4114: spi0 NAND
> + * 0xffff4130: spi0 NOR
> + * 0xffff4150: mmc1

Those last four lines are redundant, as you say exactly that, in code,
down here again. Comments are good, speaking code is better.

> + */
> +
> +#define SUNIV_BOOTED_FROM_MMC0	0xffff40f8
> +#define SUNIV_BOOTED_FROM_NAND	0xffff4114
> +#define SUNIV_BOOTED_FROM_SPI	0xffff4130
> +#define SUNIV_BOOTED_FROM_MMC1	0xffff4150
> +
>  #define is_boot0_magic(addr)	(memcmp((void *)(addr), BOOT0_MAGIC, 8) == 0)
>  
>  uint32_t sunxi_get_boot_device(void);
> +uint32_t suniv_get_boot_device(void);
>  
>  #endif
> diff --git a/arch/arm/mach-sunxi/board.c b/arch/arm/mach-sunxi/board.c
> index 57078f7a7b..b0658d583e 100644
> --- a/arch/arm/mach-sunxi/board.c
> +++ b/arch/arm/mach-sunxi/board.c
> @@ -241,6 +241,25 @@ uint32_t sunxi_get_boot_device(void)
>  	return -1;		/* Never reached */
>  }
>  
> +uint32_t suniv_get_boot_device(void)

This can be static, right?

> +{
> +	/* Get the last function call from BootRom's stack. */
> +	u32 brom_call = *(u32 *)(fel_stash.sp - 4);
> +
> +	switch (brom_call) {
> +	case SUNIV_BOOTED_FROM_MMC0:
> +		return BOOT_DEVICE_MMC1;
> +	case SUNIV_BOOTED_FROM_NAND:
> +	case SUNIV_BOOTED_FROM_SPI:
> +		return BOOT_DEVICE_SPI;
> +	case SUNIV_BOOTED_FROM_MMC1:
> +		return BOOT_DEVICE_MMC2;
> +	}

Don't you need to handle FEL boot here somehow?

Cheers,
Andre

> +
> +	printf("Unknown boot source from BROM: 0x%x\n", brom_call);
> +	return BOOT_DEVICE_MMC1;
> +}
> +
>  #ifdef CONFIG_SPL_BUILD
>  static u32 sunxi_get_spl_size(void)
>  {
> @@ -276,36 +295,13 @@ unsigned long spl_mmc_get_uboot_raw_sector(struct mmc *mmc,
>  	return sector;
>  }
>  
> -#ifdef CONFIG_MACH_SUNIV
> -/*
> - * The suniv BROM does not pass the boot media type to SPL, so we try with the
> - * boot sequence in BROM: mmc0->spinor->fail.
> - * TODO: This has the slight chance of being wrong (invalid SPL signature,
> - * but valid U-Boot legacy image on the SD card), but this should be rare.
> - * It looks like we can deduce from some BROM state upon entering the SPL
> - * (registers, SP, or stack itself) where the BROM was coming from and use
> - * that here.
> - */
> -void board_boot_order(u32 *spl_boot_list)
> -{
> -	/*
> -	 * See the comments above in sunxi_get_boot_device() for information
> -	 * about FEL boot.
> -	 */
> -	if (!is_boot0_magic(SPL_ADDR + 4)) {
> -		spl_boot_list[0] = BOOT_DEVICE_BOARD;
> -		return;
> -	}
> -
> -	spl_boot_list[0] = BOOT_DEVICE_MMC1;
> -	spl_boot_list[1] = BOOT_DEVICE_SPI;
> -}
> -#else
>  u32 spl_boot_device(void)
>  {
> -	return sunxi_get_boot_device();
> +	if (IS_ENABLED(CONFIG_MACH_SUNIV))
> +		return suniv_get_boot_device();
> +	else
> +		return sunxi_get_boot_device();
>  }
> -#endif
>  
>  __weak void sunxi_sram_init(void)
>  {