From: Biju Das <biju.das.jz@bp.renesas.com>

The calculation formula for nominal bit rate of classical CAN is same as
that of nominal bit rate of CANFD on the RZ/G3E SoC compared to other SoCs.
Add shared_bittiming variable to struct rcar_canfd_hw_info to handle this
difference.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
---
v1->v2:
 * No change.
---
 drivers/net/can/rcar/rcar_canfd.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/rcar/rcar_canfd.c b/drivers/net/can/rcar/rcar_canfd.c
index b3c8c592fb0e..ce355f79e6b6 100644
--- a/drivers/net/can/rcar/rcar_canfd.c
+++ b/drivers/net/can/rcar/rcar_canfd.c
@@ -461,6 +461,7 @@ struct rcar_canfd_hw_info {
 	unsigned ch_interface_mode:1;	/* Has channel interface mode */
 	unsigned shared_can_regs:1;	/* Has shared classical can registers */
 	unsigned external_clk:1;	/* Has external clock */
+	unsigned shared_bittiming:1;	/* Has shared nominal bittiming constants */
 };
 
 /* Channel priv data */
@@ -632,6 +633,7 @@ static const struct rcar_canfd_hw_info rcar_gen3_hw_info = {
 	.ch_interface_mode = 0,
 	.shared_can_regs = 0,
 	.external_clk = 1,
+	.shared_bittiming = 0,
 };
 
 static const struct rcar_canfd_hw_info rcar_gen4_hw_info = {
@@ -649,6 +651,7 @@ static const struct rcar_canfd_hw_info rcar_gen4_hw_info = {
 	.ch_interface_mode = 1,
 	.shared_can_regs = 1,
 	.external_clk = 1,
+	.shared_bittiming = 0,
 };
 
 static const struct rcar_canfd_hw_info rzg2l_hw_info = {
@@ -666,6 +669,7 @@ static const struct rcar_canfd_hw_info rzg2l_hw_info = {
 	.ch_interface_mode = 0,
 	.shared_can_regs = 0,
 	.external_clk = 1,
+	.shared_bittiming = 0,
 };
 
 static const struct rcar_canfd_hw_info r9a09g047_hw_info = {
@@ -683,6 +687,7 @@ static const struct rcar_canfd_hw_info r9a09g047_hw_info = {
 	.ch_interface_mode = 1,
 	.shared_can_regs = 1,
 	.external_clk = 0,
+	.shared_bittiming = 1,
 };
 
 /* Helper functions */
@@ -1912,7 +1917,10 @@ static int rcar_canfd_channel_probe(struct rcar_canfd_global *gpriv, u32 ch,
 		priv->can.fd.do_get_auto_tdcv = rcar_canfd_get_auto_tdcv;
 	} else {
 		/* Controller starts in Classical CAN only mode */
-		priv->can.bittiming_const = &rcar_canfd_bittiming_const;
+		if (gpriv->info->shared_bittiming)
+			priv->can.bittiming_const = gpriv->info->nom_bittiming;
+		else
+			priv->can.bittiming_const = &rcar_canfd_bittiming_const;
 		priv->can.ctrlmode_supported = CAN_CTRLMODE_BERR_REPORTING;
 	}
 
-- 
2.43.0

Hi Biju,

On Thu, 21 Aug 2025 at 16:14, Biju <biju.das.au@gmail.com> wrote:
> From: Biju Das <biju.das.jz@bp.renesas.com>
>
> The calculation formula for nominal bit rate of classical CAN is same as
> that of nominal bit rate of CANFD on the RZ/G3E SoC compared to other SoCs.
> Add shared_bittiming variable to struct rcar_canfd_hw_info to handle this
> difference.
>
> Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
> Reviewed-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>

Thanks for your patch!

> --- a/drivers/net/can/rcar/rcar_canfd.c
> +++ b/drivers/net/can/rcar/rcar_canfd.c
> @@ -461,6 +461,7 @@ struct rcar_canfd_hw_info {
>         unsigned ch_interface_mode:1;   /* Has channel interface mode */
>         unsigned shared_can_regs:1;     /* Has shared classical can registers */
>         unsigned external_clk:1;        /* Has external clock */
> +       unsigned shared_bittiming:1;    /* Has shared nominal bittiming constants */
>  };
>
>  /* Channel priv data */
> @@ -632,6 +633,7 @@ static const struct rcar_canfd_hw_info rcar_gen3_hw_info = {
>         .ch_interface_mode = 0,
>         .shared_can_regs = 0,
>         .external_clk = 1,
> +       .shared_bittiming = 0,
>  };
>
>  static const struct rcar_canfd_hw_info rcar_gen4_hw_info = {
> @@ -649,6 +651,7 @@ static const struct rcar_canfd_hw_info rcar_gen4_hw_info = {
>         .ch_interface_mode = 1,
>         .shared_can_regs = 1,
>         .external_clk = 1,
> +       .shared_bittiming = 0,

I could find no stricter limitation of the bit timings in classical
CAN mode on R-Car Gen4, so it looks like this should be 1, too...

>  };
>
>  static const struct rcar_canfd_hw_info rzg2l_hw_info = {
> @@ -666,6 +669,7 @@ static const struct rcar_canfd_hw_info rzg2l_hw_info = {
>         .ch_interface_mode = 0,
>         .shared_can_regs = 0,
>         .external_clk = 1,
> +       .shared_bittiming = 0,
>  };
>
>  static const struct rcar_canfd_hw_info r9a09g047_hw_info = {
> @@ -683,6 +687,7 @@ static const struct rcar_canfd_hw_info r9a09g047_hw_info = {
>         .ch_interface_mode = 1,
>         .shared_can_regs = 1,
>         .external_clk = 0,
> +       .shared_bittiming = 1,
>  };
>
>  /* Helper functions */
> @@ -1912,7 +1917,10 @@ static int rcar_canfd_channel_probe(struct rcar_canfd_global *gpriv, u32 ch,
>                 priv->can.fd.do_get_auto_tdcv = rcar_canfd_get_auto_tdcv;
>         } else {
>                 /* Controller starts in Classical CAN only mode */
> -               priv->can.bittiming_const = &rcar_canfd_bittiming_const;
> +               if (gpriv->info->shared_bittiming)

... hence you can just check the existing shared_can_regs flag here,
and don't need to introduce a new flag for shared bittimings?

> +                       priv->can.bittiming_const = gpriv->info->nom_bittiming;
> +               else
> +                       priv->can.bittiming_const = &rcar_canfd_bittiming_const;
>                 priv->can.ctrlmode_supported = CAN_CTRLMODE_BERR_REPORTING;
>         }

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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