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

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Message-ID:
 <TY3PR01MB113466CCD4124417203663E2686C9A@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Mon, 17 Nov 2025 10:50:38 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: geert <geert@...ux-m68k.org>
CC: Marc Kleine-Budde <mkl@...gutronix.de>, Vincent Mailhol
	<mailhol@...nel.org>, 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 Geert,

Thanks for the feedback.

> -----Original Message-----
> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: 17 November 2025 10:13
> Subject: Re: [PATCH] can: rcar_canfd: Fix controller mode setting for RZ/G2L SoCs
> 
> Hi Biju,
> 
> On Sun, 16 Nov 2025 at 11:31, Biju Das <biju.das.jz@...renesas.com> wrote:
> > > From: Biju Das
> > > > Sent: 12 November 2025 08:47
> > > > On 30.10.2025 12:05:04, Biju wrote:
> > > > > 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.
> 
> Hmm, Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yaml:
> 
>   renesas,no-can-fd:
>     $ref: /schemas/types.yaml#/definitions/flag
>     description:
>       The controller can operate in either CAN FD only mode (default) or
>       Classical CAN only mode.  The mode is global to all channels.
>       Specify this property to put the controller in Classical CAN only mode.

Maybe we need to remove the "only" word from bindings to avoid confusion.
This is coming from R-Car Gen3, which has 2 modes. As per the bit definition
of RCMC

0: Classical CAN mode
1: CAN FD mode

 
As per 48.1.2 Interface Mode od RZ/G2{H,M,N,E} manual
RS-CANFD has the following two interface modes.

• Classical CAN mode: Only classical CAN frames are handled.
• CAN FD mode: both the classical CAN frames and CAN FD frames are handled.

 
But RZ/G2L, RZ/G3E and R-Car Gen4, has additional mode called FD-only mode
for CAN-FD. In this mode, rx/tx transfer using the canfdtest tool won't work.
But cansend/candump works[1].


To summarise, we need the following setting in rcar_canfd_reset_controller():

R-Car Gen3 and RZ/G2L: On Global reset mode set RCMC for CAN-FD or Classical CAN
RZ/G2L: On channel reset mode, set FD-only mode or CAN-FD mode.
RZ/G3E and R-Car Gen4: On channel reset mode, set CAN-FD mode or FD-only mode or Classical CAN mode

I think there will be 2 patches:
1) Fixes patches to set CAN-FD mode as the default for all SoCs 
2) Binding + Driver changes for supporting FD-Only mode for RZ/G2L, R/G3E and R-Car Gen4.

[1]
root@...rc-rzg3e:~# candump can1 &
[1] 399
root@...rc-rzg3e:~# [  232.698723] can: controller area network core
[  232.703202] NET: Registered PF_CAN protocol family
[  232.770075] can: raw protocol
root@...rc-rzg3e:~# cansend can0 123##0.0011223344556677
  can1  123  [08]  00 11 22 33 44 55 66 77
root@...rc-rzg3e:~#

Please share your thoughts.

Cheers,
Biju