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

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Message-ID:
 <TY3PR01MB113461B3528C3057DA03F6E808642A@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Fri, 4 Jul 2025 10:12:34 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Vincent Mailhol <mailhol.vincent@...adoo.fr>
CC: Fabrizio Castro <fabrizio.castro.jz@...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>, biju.das.au
	<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 Vincent,

Thanks for the feedback.

> -----Original Message-----
> From: Vincent Mailhol <mailhol.vincent@...adoo.fr>
> Sent: 04 July 2025 03:25
> 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)

Are you ok for the below change to reduce the changes minimum??

-#define RCANFD_CFG_SJW(x)		(((x) & 0x3) << 24)
+#define RCANFD_CFG_SJW(x)		FIELD_PREP(GENMASK(25, 24), x))

Or

you want RCANFD_CFG_SJW_MASK as separate one as you suggested?

Cheers,
Biju

> 
> (same for the other fields).
> 
> >  	rcar_canfd_write(priv->base, RCANFD_CCFG(ch), cfg);
> 
> 
> Yours sincerely,
> Vincent Mailhol