linux-kernel - Re: [PATCH 2/4] usb: host: ehci-platform: Call reset assert/deassert on suspend/resume

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMuHMdXG8w9jR9gr4av15VT69XNouqys5z4Rxx-nidnvnbN3dA@mail.gmail.com>
Date: Fri, 7 Nov 2025 09:01:08 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Claudiu Beznea <claudiu.beznea@...on.dev>
Cc: stern@...land.harvard.edu, gregkh@...uxfoundation.org, 
	p.zabel@...gutronix.de, yoshihiro.shimoda.uh@...esas.com, 
	prabhakar.mahadev-lad.rj@...renesas.com, kuninori.morimoto.gx@...esas.com, 
	geert+renesas@...der.be, linux-usb@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 2/4] usb: host: ehci-platform: Call reset assert/deassert
 on suspend/resume

Hi Claudiu,

On Thu, 6 Nov 2025 at 19:56, Claudiu Beznea <claudiu.beznea@...on.dev> wrote:
> On 11/6/25 16:52, Geert Uytterhoeven wrote:
> > On Thu, 6 Nov 2025 at 15:36, Claudiu <claudiu.beznea@...on.dev> wrote:
> >> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> >>
> >> The Renesas RZ/G3S SoC supports a power-saving mode in which power to most
> >> of the SoC components is turned off, including the USB blocks. On the
> >> resume path, the reset signal must be de-asserted before applying any
> >> settings to the USB registers. To handle this properly, call
> >> reset_control_assert() and reset_control_deassert() during suspend and
> >> resume, respectively.
> >>
> >> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> >
> >> --- a/drivers/usb/host/ehci-platform.c
> >> +++ b/drivers/usb/host/ehci-platform.c
> >> @@ -454,6 +454,17 @@ static int __maybe_unused ehci_platform_suspend(struct device *dev)
> >>         if (pdata->power_suspend)
> >>                 pdata->power_suspend(pdev);
> >>
> >> +       ret = reset_control_assert(priv->rsts);
> >> +       if (ret) {
> >> +               if (pdata->power_on)
> >> +                       pdata->power_on(pdev);
> >> +
> >> +               ehci_resume(hcd, false);
> >> +
> >> +               if (priv->quirk_poll)
> >> +                       quirk_poll_init(priv);
> >
> > I have my doubts about the effectiveness of this "reverse error
> > handling".  If the reset_control_assert() failed, what are the chances
> > that the device will actually work after trying to bring it up again?
> >
> > Same comment for next patch.
>
> I wasn't sure if I should do this revert or not. In my mind, if the reset
> assert fails, the reset signal is still de-asserted.

Possibly.  Most reset implementations either cannot fail, or can
fail due to a timeout.  What state the device is in in case of the latter is
hard to guess...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds