[PATCH 6/7] Input: add `SW_BOOT_ALT`

[Quentin Schulz]

Hi Kever,

On 9/24/22 10:05, Kever Yang wrote:
> Hi Quentin,
> 
> 
> On 2022/9/22 20:12, Quentin Schulz wrote:
>> From: Quentin Schulz <quentin.schulz at theobroma-systems.com>
>>
>> This event code represents the firmware source to use at boot.
>> Value 0 means using "standard" firmware source, value 1 means using
>> "alternative" firmware source.
>>
>> For example, some hardware has the ability to force the BOOTROM to load
>> the bootloader from a secondary firmware source (say SD card) instead of
>> trying with the standard first and then the secondary. This event allows
>> the userspace to know which firmware source was requested *in hardware*.
> 
> Does this series patches need this patch?
> 
> I don't understand how can you affect the BOOTROM on PX30, I think PX30 
> does not
> 
> support this feature.
> 

This is being discussed upstream with the kernel folks, this will likely 
not be taken unfortunately. But let me explain how things work on our board:

We have a switch we can toggle to *electrically* disable eMMC/SPI 
flashes and force booting from SD card, even if there is some TPL/SPL on 
eMMC/SPI. This is required by the Q7 standard (via the 
BIOS_DISABLE/BOOT_ALT signal).

Therefore, the SoC is not even aware of this switch (and does not need 
to), it just cannot communicate with the eMMC/SPI so it continues to try 
other boot media, with e.g. SD card or fallbacks to USB if nothing's 
found. Nothing Rockchip specific here.

This version of the series needs the patch because it defines a new 
event code that is then used in the device tree, see gpio-keys Device 
Tree node where you have switch-bios-disable-n.

Cheers,
Quentin