linux-kernel - RE: [PATCH] can: rcar_canfd: Fix controller mode setting for RZ/G2L SoCs

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Message-ID:
 <TY3PR01MB11346974232A057A7D5B6EBAD86CBA@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Sat, 15 Nov 2025 13:57:13 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Marc Kleine-Budde <mkl@...gutronix.de>, Geert Uytterhoeven
	<geert+renesas@...der.be>
CC: Vincent Mailhol <mailhol@...nel.org>, Geert Uytterhoeven
	<geert+renesas@...der.be>, magnus.damm <magnus.damm@...il.com>, Tranh Ha
	<tranh.ha.xb@...esas.com>, Duy Nguyen <duy.nguyen.rh@...esas.com>,
	"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>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH] can: rcar_canfd: Fix controller mode setting for RZ/G2L
 SoCs

Hi Marc, Geert,

> -----Original Message-----
> From: Marc Kleine-Budde <mkl@...gutronix.de>
> Sent: 12 November 2025 08:47
> Subject: Re: [PATCH] can: rcar_canfd: Fix controller mode setting for RZ/G2L SoCs
> 
> On 30.10.2025 12:05:04, Biju wrote:
> > From: Biju Das <biju.das.jz@...renesas.com>
> >
> > The commit 5cff263606a1 ("can: rcar_canfd: Fix controller mode
> > setting") applies to all SoCs except the RZ/G2L family of SoCs. As per
> > RZ/G2L hardware manual "Figure 28.16 CAN Setting Procedure after the
> > MCU is Reset" CAN mode needs to be set before channel reset. Add the
> > mode_before_ch_rst variable to struct rcar_canfd_hw_info to handle
> > this difference.
> >
> > The above commit also breaks CANFD functionality on RZ/G3E. Adapt this
> > change to RZ/G3E, as well as it works ok by following the
> > initialisation sequence of RZ/G2L.
> >
> > Fixes: 5cff263606a1 ("can: rcar_canfd: Fix controller mode setting")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> 
> Applied to linux-can.

There are 3 modes for CANFD on RZ/G3E

1) CAN-FD mode
2) FD only mode
3) Classical CAN only mode

In the "FD only mode", the FDOE bit enables the reception and transmission of CAN-FD-only frames.
If enabled, communication in the Classical CAN frame format is disabled.

On RZ/G2L, currently, CAN-FD mode is enabled by default and
On RZ/G3E and R-Car Gen4, currently FD-only mode is the default.

Prior to commit 5cff263606a1010 ("can: rcar_canfd: Fix controller mode setting)
RZ/G3E and R-Car Gen4 are using incorrect code for setting CAN-FD mode. But fortunately,
it sets the mode as CAN-FD node, as the channel reset was executed after
setting the mode, that resets the registers to CAN-FD mode.(Global reset, set mode, channel reset)

The commit 5cff263606a1010 makes (Global reset, channel reset, set mode), now
align with the flow mentioned in the hardware manual for all SoCs except RZ/G2L.
But because of the earlier wrong code, it sets to FD-only mode instead of CAN-FD mode.

Is it okay to drop this patch so I can send another patch to make CAN-FD mode
as the default for RZ/G3E and R-Car Gen4?

As an enhancement, we need to define a device tree property to support FD-only mode
for RZ/G2L, RZ/G3E and R-Car Gen4. Please share your thoughts on this.

Cheers,
Biju