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

Thu Feb 10 22:15:33 CET 2022

On Thu, 10 Feb 2022 14:20:26 -0500
Jesse Taube <mr.bossman075 at gmail.com> wrote:

Hi,

> On 2/10/22 05:57, Andre Przywara wrote:
> > 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?

Actually, looking closer, I think this should be restructured:
You keep this function, as a static, but let it return the sunxi
internal boot source codes (that the BROM would write on other SoCs):
	case SUNIV_BOOTED_FROM_MMC0:
		return SUNXI_BOOTED_FROM_MMC0;
	...
Possibly rename it to suniv_get_boot_source.
Then you change sunxi_get_boot_source() to:
	...
	if (IS_ENABLED(CONFIG_MACH_SUNIV))
		return suniv_get_boot_source();
	else
		return readb(SPL_ADDR + 0x28);

This way we fix this one level deeper, and can call
sunxi_get_boot_source() from elsewhere as well.

Hope that makes sense.

> >   
> >> +{
> >> +	/* Get the last function call from BootRom's stack. */
> >> +	u32 brom_call = *(u32 *)(fel_stash.sp - 4);You are okay with this I was expecting you to explain a better way that   
> i don't know about.

That looks alright, I think we explained how it works by now (commit
message plus two comments), plus the code makes that clear.

> >> +
> >> +	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?  
> Yes but I have no clue what the SP is also wouldn't we have it hang 
> anyway.

The stack would be from some SPL thunk code, which is not necessarily
stable (in fact we are still working on that). However we support FEL
booting already, because our FEL thunk code writes a signature into
SRAM - even when the BROM does not do that.
So we just keep that check from the current code, see the first part
of board_boot_order().

> The other changes requested i have fixed, I'm sorry about the 
> subpar commit descriptions.

No worries, it's just from experience that we want good commit
messages, so that others (or even yourself!) can make sense of code in
the future.

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)
> >>   {  
> >   