linux-kernel - Re: [PATCH 4/4] can: rcar_canfd: Replace RCANFD_CFG_* macros with FIELD

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Message-ID: <dc6d1cdf-0c93-4d7a-b3c4-722d1e58f5cf@wanadoo.fr>
Date: Fri, 4 Jul 2025 11:24:49 +0900
From: Vincent Mailhol <mailhol.vincent@...adoo.fr>
To: Biju Das <biju.das.jz@...renesas.com>
Cc: Fabrizio Castro <fabrizio.castro.jz@...esas.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>,
 Biju Das <biju.das.au@...il.com>, Marc Kleine-Budde <mkl@...gutronix.de>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Magnus Damm <magnus.damm@...il.com>
Subject: Re: [PATCH 4/4] can: rcar_canfd: Replace RCANFD_CFG_* macros with
 FIELD_PREP

Hi Biju,

On 04/07/2025 at 03:34, Biju Das wrote:
> Replace RCANFD_CFG_* macros with simpler FIELD_PREP macro.
> 
> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> ---
>  drivers/net/can/rcar/rcar_canfd.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/can/rcar/rcar_canfd.c b/drivers/net/can/rcar/rcar_canfd.c
> index b5b059e83374..dd87b4e8e688 100644
> --- a/drivers/net/can/rcar/rcar_canfd.c
> +++ b/drivers/net/can/rcar/rcar_canfd.c
> @@ -102,12 +102,6 @@
>  
>  /* Channel register bits */
>  
> -/* RSCFDnCmCFG - Classical CAN only */
> -#define RCANFD_CFG_SJW(x)		(((x) & 0x3) << 24)
> -#define RCANFD_CFG_TSEG2(x)		(((x) & 0x7) << 20)
> -#define RCANFD_CFG_TSEG1(x)		(((x) & 0xf) << 16)
> -#define RCANFD_CFG_BRP(x)		(((x) & 0x3ff) << 0)
> -
>  /* RSCFDnCFDCmCTR / RSCFDnCmCTR */
>  #define RCANFD_CCTR_CTME		BIT(24)
>  #define RCANFD_CCTR_ERRD		BIT(23)
> @@ -1418,8 +1412,8 @@ static void rcar_canfd_set_bittiming(struct net_device *ndev)
>  	if ((priv->can.ctrlmode & CAN_CTRLMODE_FD) || gpriv->info->shared_can_regs) {
>  		cfg = rcar_canfd_compute_nominal_bit_rate_cfg(gpriv->info, tseg1, brp, sjw, tseg2);
>  	} else {
> -		cfg = (RCANFD_CFG_TSEG1(tseg1) | RCANFD_CFG_BRP(brp) |
> -		       RCANFD_CFG_SJW(sjw) | RCANFD_CFG_TSEG2(tseg2));
> +		cfg = FIELD_PREP(GENMASK(19, 16), tseg1) | FIELD_PREP(GENMASK(9, 0), brp) |
> +		      FIELD_PREP(GENMASK(25, 24), sjw) | FIELD_PREP(GENMASK(22, 20), tseg2);
>  	}

You can still keep the macro definition to give a meaning to the magic number:

  #define RCANFD_CFG_SJW_MASK GENMASK(25, 24)

and do a:

  FIELD_PREP(RCANFD_CFG_SJW_MASK, sjw)

(same for the other fields).

>  	rcar_canfd_write(priv->base, RCANFD_CCFG(ch), cfg);


Yours sincerely,
Vincent Mailhol