Booting RPi4 from USB MSD by 5.10

[Ryutaroh Matsumoto]

Hi Nicolas,

I have one question regarding your emai.

From: Nicolas Saenz Julienne <nsaenzjulienne at suse.de>
Subject: Re: Booting RPi4 from USB MSD by 5.10
Date: Wed, 03 Feb 2021 13:04:21 +0100
> It seems I misread your original mail. Turns out reset-raspberrypi and xhci_pci
> configs are already linked as they should:
> 
> 	config RESET_RASPBERRYPI
> 		tristate "Raspberry Pi 4 Firmware Reset Driver"
> 		depends on RASPBERRYPI_FIRMWARE || (RASPBERRYPI_FIRMWARE=n && COMPILE_TEST)
> 	>>	default USB_XHCI_PCI
> 		help
> 		  [...]
> 
> Your initramfs fix looks OK to me.

With Linux 5.9, CONFIG_RESET_RASPBERRYPI did not exist,
and USB booting of RPi4 was possible regardless of CONFIG_RESET_RASPBERRYPI.

With Linux 5.10 and CONFIG_USB_XHCI_PCI=m, either
(a) CONFIG_RESET_RASPBERRYPI=y (which works well in general but my buggy
    USB MSD does not boot with it),
(b) OR reset_raspberrypi in /etc/initramfs-tools/modules (which also works with
    my buggy USB MSD)
is required.

Is this introduced change is intentional?
Currently the official Debian testing packages do not allow USB boot of RPi4,
though I submitted a merge request fixing the situation...

Best regards, Ryutaroh