[PATCH] rockchip: spl: Cache boot source id for later use

[Dragan Simic]

Hello Jonas,

Please see a few comments below.

On 2024-03-15 18:34, Jonas Karlman wrote:
> Rockchip BROM write a boot source id at CFG_IRAM_BASE + 0x10, the id
> indicate from what storage media TPL/SPL was loaded from.

s/write/writes/
s/indicate/indicates/

There are also a few more similar small grammar issues in the rest
of the patch descroption below.

> SPL use this value to determine what device "same-as-spl" represent 
> when
> determining from where FIT should be loaded. This works as long as the
> boot_devices array contain a matching id <-> node path entry.

s/use/uses/
etc.

> However, SPL typically load a small part of TF-A into SRAM and on 
> RK3399
> this overwrites the CFG_IRAM_BASE + 0x10 addr used for boot source id.
> 
> Here boot source id is 3 before FIT images is loaded, and 0 after:
> 
>   U-Boot SPL 2024.04-rc4 (Mar 15 2024 - 17:26:19 +0000)
>   board_spl_was_booted_from: brom_bootdevice_id 3 maps to
> '/spi at ff1d0000/flash at 0'
>   Trying to boot from SPI
>   ## Checking hash(es) for config config-1 ... OK
>   ## Checking hash(es) for Image atf-1 ... sha256+ OK
>   ## Checking hash(es) for Image u-boot ... sha256+ OK
>   ## Checking hash(es) for Image fdt-1 ... sha256+ OK
>   ## Checking hash(es) for Image atf-2 ... sha256+ OK
>   ## Checking hash(es) for Image atf-3 ... sha256+ OK
>   board_spl_was_booted_from: failed to resolve brom_bootdevice_id 0
>   spl_decode_boot_device: could not find udevice for /mmc at fe330000
>   spl_decode_boot_device: could not find udevice for /mmc at fe320000
>   spl_perform_fixups: could not map boot_device to ofpath: -19
> 
> Use a static bootdevice_brom_id to cache the boot source id after an
> initial read from SRAM to fix this, this allow spl_perform_fixups() to
> resolve correct boot source path for "same-as-spl" after SPL have 
> loaded
> TF-A related FIT images into memory.
> 
> With this the spl-boot-device prop can correctly be resolved to the
> SPI flash node in the control FDT:
> 
>   => fdt addr ${fdtcontroladdr}
>   Working FDT set to f1ee6710
>   => fdt list /chosen
>   chosen {
>       u-boot,spl-boot-device = "/spi at ff1d0000/flash at 0";
>       stdout-path = "serial2:1500000n8";
>       u-boot,spl-boot-order = "same-as-spl", "/mmc at fe330000", 
> "/mmc at fe320000";
>   };
> 
> Signed-off-by: Jonas Karlman <jonas at kwiboo.se>
> ---
>  arch/arm/mach-rockchip/spl.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-rockchip/spl.c 
> b/arch/arm/mach-rockchip/spl.c
> index 1586a093fc37..27e996b504e7 100644
> --- a/arch/arm/mach-rockchip/spl.c
> +++ b/arch/arm/mach-rockchip/spl.c
> @@ -32,9 +32,17 @@ __weak const char * const
> boot_devices[BROM_LAST_BOOTSOURCE + 1] = {
> 
>  const char *board_spl_was_booted_from(void)
>  {
> -	u32  bootdevice_brom_id = readl(BROM_BOOTSOURCE_ID_ADDR);
> +	static u32 bootdevice_brom_id;
>  	const char *bootdevice_ofpath = NULL;
> 
> +	if (!bootdevice_brom_id)
> +		bootdevice_brom_id = readl(BROM_BOOTSOURCE_ID_ADDR);
> +	if (!bootdevice_brom_id) {
> +		debug("%s: unknown brom_bootdevice_id %x\n",
> +		      __func__, bootdevice_brom_id);
> +		return NULL;
> +	}
> +

Maybe it would be better to execute readl(BROM_BOOTSOURCE_ID_ADDR)
only once, i.e. to have something like this instead:

     +	static u32 bootdevice_brom_id = -1;

     +	if (bootdevice_brom_id == -1) {
     +		bootdevice_brom_id = readl(BROM_BOOTSOURCE_ID_ADDR);
     +		if (!bootdevice_brom_id)
     +			debug("%s: unknown brom_bootdevice_id %x\n",
     +			      __func__, bootdevice_brom_id);
     +	}
     +
     +	if (!bootdevice_brom_id)	/* fail on subsequent tries */
     +		return NULL;
     +

The logic behind such an approach would be to try only once and fail
on subsequent (re)tries.  That way, it would also serve as some kind of
a runtime canary test, because the first try should succeed, which may
prove useful in the field.

>  	if (bootdevice_brom_id < ARRAY_SIZE(boot_devices))
>  		bootdevice_ofpath = boot_devices[bootdevice_brom_id];