[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 05:16 PM, Marek Vasut wrote:
> 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.

By doing so, we can probably even clean this up and have default __weak
spl_boot_mode() implementation rather than having a custom copy for each
SoC.

-- 
Best regards,
Marek Vasut