linux-kernel - Re: [PATCH] usb: renesas-xhci: Prefer firmware loading on unknown ROM state

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Date:   Thu, 26 Aug 2021 13:55:54 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Mathias Nyman <mathias.nyman@...el.com>,
        Moritz Fischer <mdf@...nel.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: renesas-xhci: Prefer firmware loading on unknown ROM state

On Thu, 26 Aug 2021 13:50:13 +0200,
Greg Kroah-Hartman wrote:
> 
> On Thu, Aug 19, 2021 at 01:34:27PM +0200, Takashi Iwai wrote:
> > The recent attempt to handle an unknown ROM state in the commit
> > d143825baf15 ("usb: renesas-xhci: Fix handling of unknown ROM state")
> > resulted in a regression and reverted later by the commit 44cf53602f5a
> > ("Revert "usb: renesas-xhci: Fix handling of unknown ROM state"").
> > The problem of the former fix was that it treated the failure of
> > firmware loading as a fatal error.  Since the firmware files aren't
> > included in the standard linux-firmware tree, most users don't have
> > them, hence they got the non-working system after that.  The revert
> > fixed the regression, but also it didn't make the firmware loading
> > triggered even on the devices that do need it.  So we need still a fix
> > for them.
> > 
> > This is another attempt to handle the unknown ROM state.  Like the
> > previous fix, this also tries to load the firmware when ROM shows
> > unknown state.  In this patch, however, the failure of a firmware
> > loading (such as a missing firmware file) isn't handled as a fatal
> > error any longer when ROM has been already detected, but it falls back
> > to the ROM mode like before.  The error is returned only when no ROM
> > is detected and the firmware loading failed.
> > 
> > Along with it, for simplifying the code flow, the detection and the
> > check of ROM is factored out from renesas_fw_check_running() and done
> > in the caller side, renesas_xhci_check_request_fw().  It avoids the
> > redundant ROM checks.
> > 
> > The patch was tested on Lenovo Thinkpad T14 gen (BIOS 1.34).  Also it
> > was confirmed that no regression is seen on another Thinkpad T14
> > machine that has worked without the patch, too.
> > 
> > Fixes: 44cf53602f5a ("Revert "usb: renesas-xhci: Fix handling of unknown ROM state"")
> > BugLink: https://bugzilla.opensuse.org/show_bug.cgi?id=1189207
> > Signed-off-by: Takashi Iwai <tiwai@...e.de>
> > ---
> >  drivers/usb/host/xhci-pci-renesas.c | 35 +++++++++++++++++++----------
> >  1 file changed, 23 insertions(+), 12 deletions(-)
> 
> This does not apply to my usb-linus branch, are you sure it is still
> needed in Linus's tree right now?

I guess we can postpone for 5.15.  The patch was written for the code
on linux-next, and I see there have been a few code clean up there.

But the patch itself could be applied to Linus tree with a slight
fuzz, so the stable backport should be fine.

If it's still not cleanly applicable, let me know.  I'll refresh the
patch for whatever preferred branch.


thanks,

Takashi