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

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Message-ID:
 <TY3PR01MB113461FBB064E71820BBB0ECB8615A@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Mon, 15 Sep 2025 12:37:49 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: geert <geert@...ux-m68k.org>, biju.das.au <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>, "linux-can@...r.kernel.org"
	<linux-can@...r.kernel.org>, "linux-renesas-soc@...r.kernel.org"
	<linux-renesas-soc@...r.kernel.org>, "linux-kernel@...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 Geert,

Thanks for the feedback.

> -----Original Message-----
> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: 15 September 2025 13:08
> 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...


RZ/G3E uses ch0 and ch4. So problem maybe specific to ch3.

Cheers,
Biju