[U-Boot] [PATCH] imx-common: spl: Allow booting from eMMC when SPL is loaded from non-eMMC device

[Marek Vasut <marex@denx.de>]

On 01/26/2018 05:05 PM, Stefano Babic wrote:
> On 26/01/2018 15:57, Lukasz Majewski wrote:
>> This patch tries to solve the problem described in following patch:
>> https://patchwork.ozlabs.org/patch/796237/
>>
>> The main argument against the above code was the potential lack of
>> consistency if we boot SPL from the SD card (and then eMMC may load
>> u-boot proper).
>>
>> This patch preserves this consistency if spl_boot_device() detects boot
>> from either SD card or eMMC.
>>
>> It only will change boot device if boot from non-SD/eMMC device is
>> detected - i.e SPI-NOR (as in this case).
>>
>> Signed-off-by: Lukasz Majewski <lukma@denx.de>
>> ---
>>
>>  arch/arm/mach-imx/spl.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mach-imx/spl.c b/arch/arm/mach-imx/spl.c
>> index 6c16872f59..735d9f6261 100644
>> --- a/arch/arm/mach-imx/spl.c
>> +++ b/arch/arm/mach-imx/spl.c
>> @@ -134,7 +134,12 @@ 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)
>>  {
>> -	switch (spl_boot_device()) {
>> +	u32 spl_bd = spl_boot_device();
>> +
>> +	if (spl_bd != BOOT_DEVICE_MMC1)
>> +		spl_bd = boot_device;
>> +
>> +	switch (spl_bd) {
>>  	/* for MMC return either RAW or FAT mode */
>>  	case BOOT_DEVICE_MMC1:
>>  	case BOOT_DEVICE_MMC2:
>>
> 
> But have we not board_boot_order() for such as cases ? It is a wek
> function and you can define it in your board code. Put in mach-imx, it
> is valid for all boards.

After a bit of offline discussion with Lukasz, I think I understand what
the problem is.

The SPL common code calls spl_boot_device() to determine which boot
device to boot from next ; in his case, SPI or eMMC. In case eMMC is
selected, the SPL MMC common code then calls spl_boot_mode() (different
function than spl_boot_device()) to determine whether the content on
SD/eMMC is RAW or on a FS.

The iMX implementation (and layerspace too) does extra stuff in the
implementation of spl_boot_mode() by calling spl_boot_device() again,
which is wrong.

spl_boot_mode() is only used by spl_mmc.c , so we are certain the system
is booting from SD/MMC . By turning this around, if the board code did
override the board_boot_order() to load the next payload from
SD/MMC/eMMC AND started SPL from non-SD/MMC/eMMC device , calling
spl_boot_device() in spl_boot_mode() implementation will return bogus
result and the spl_boot_mode() will fail in the default: case.

Thus, the fix here is to do what ie. socfpga does, just discern whether
the content on SD/MMC/eMMC is RAW or FS and do not do any extra checks.

-- 
Best regards,
Marek Vasut