linux-kernel - Re: [PATCH v2 0/7] Add suspend/resume support

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Message-ID: <CAMuHMdXx88-3j6Gu_ZK6tRV=RWu+T_yETaNEMw=rviRsNM7u6g@mail.gmail.com>
Date: Mon, 15 Sep 2025 14:07:45 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Biju <biju.das.au@...il.com>
Cc: Marc Kleine-Budde <mkl@...gutronix.de>, Vincent Mailhol <mailhol.vincent@...adoo.fr>, 
	Magnus Damm <magnus.damm@...il.com>, Philipp Zabel <p.zabel@...gutronix.de>, 
	Biju Das <biju.das.jz@...renesas.com>, linux-can@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v2 0/7] Add suspend/resume support

Hi Biju,

On Fri, 12 Sept 2025 at 12:47, Biju <biju.das.au@...il.com> wrote:
> From: Biju Das <biju.das.jz@...renesas.com>
> This patch series adds proper suspend/resume support to the Renesas
> R-Car CAN-FD controller driver, after the customary cleanuops and fixes.
> It aims to fix CAN-FD operation after resume from s2ram on systems where
> PSCI powers down the SoC.
>
> This patch series has been tested on RZ/G3E SMARC EVK, Ebisu-4D (R-Car E3)
> and White Hawk (R-Car V4H).
>
> v1->v2:
>  * Added logs from RZ/G3E
>  * Collected tags.
>  * Moved enabling of RAM clk from probe().
>  * Added RAM clk handling in rcar_canfd_global_{,de}init().
>  * Fixed the typo in error path of rcar_canfd_resume().

Thanks for updating!

This series behaves the same as v1 on Ebisu-4D (R-Car E3) and White
Hawk (R-Car V4H).  However, that means the small regression I mentioned
before [1] is still present:

   "While this fixes CAN-FD after resume from s2ram on R-Car E3 (Ebisu-4D),
    it does introduce a regression on R-Car V4H (White Hawk): after resume
    from s2idle (White Hawk does not support s2ram), CAN frames sent by
    other devices are no longer received, and the other side sometimes
    reports a "bus-off"."

Note that I did my testing between CAN-FD channel 0 on Ebisu, and
CAN-FD channel 3 on White-Hawk.

I retried with wiring between CAN-FD channel 0 and 1 on White-Hawk,
and with that configuration, CAN-FD still works after s2idle.

   "However, the underlying issue is pre-existing, and can be reproduced
    without this patch: the CAN-FD controller fails in the same way after
    driver unbind/rebind.  So something must be missing in the
    (de)initialization sequence for the R-Car Gen4 CAN-FD register layout.
    Note that it keeps on working after ifdown/ifup, which does not
    reinitialize the full controller."

Same here: CAN-FD channel 0 and 1 on White-Hawk keep on working after
unbind/rebind, unlike channel 3.  So it looks like we have an issue
again with handling channels 2 and higher...

[1] https://lore.kernel.org/all/f9198ea3be46f1eb2e27d046e51293df7fb67f46.1755855779.git.geert+renesas@glider.be

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