Booting RPi4 from USB MSD by 5.10

[Nicolas Saenz Julienne]

Hi Ryutaroh,
sorry for the late reply.

On Fri, 2021-02-05 at 10:48 +0900, Ryutaroh Matsumoto wrote:
> 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?

Yes, reset-raspberrypi was introduced in v5.10. Before that we depended on a
series of PCI quirks which were pretty nasty.

Regards,
Nicolas

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