linux-kernel - RE: [PATCH v2 3/4] can: rcar_canfd: Simplify nominal bit rate config

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Message-ID:
 <TY3PR01MB11346916359AE1075F3548EC8860CA@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Mon, 8 Sep 2025 10:42:04 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: geert <geert@...ux-m68k.org>, biju.das.au <biju.das.au@...il.com>
CC: Marc Kleine-Budde <mkl@...gutronix.de>, Vincent Mailhol
	<mailhol.vincent@...adoo.fr>, magnus.damm <magnus.damm@...il.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>
Subject: RE: [PATCH v2 3/4] can: rcar_canfd: Simplify nominal bit rate config

Hi Geert,

Thanks for the feedback.

> -----Original Message-----
> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: 01 September 2025 14:38
> Subject: Re: [PATCH v2 3/4] can: rcar_canfd: Simplify nominal bit rate config
> 
> Hi Biju,
> 
> On Thu, 21 Aug 2025 at 16:14, Biju <biju.das.au@...il.com> wrote:
> > From: Biju Das <biju.das.jz@...renesas.com>
> >
> > Introduce rcar_canfd_compute_nominal_bit_rate_cfg() for simplifying
> > nominal bit rate configuration by replacing function-like macros.
> >
> > Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> > ---
> > v1->v2:
> >  * Split from patch#3 for computing nominal bit rate config separate.
> >  * Updated rcar_canfd_compute_nominal_bit_rate_cfg() to handle
> >    nominal bit rate configuration for both classical CAN and CANFD.
> >  * Replaced RCANFD_NCFG_NBRP->RCANFD_NCFG_NBRP_MASK and used FIELD_PREP to
> >    extract value.
> 
> Thanks for your patch!
> 
> Your patch is correct, so
> Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
> 
> Still a few suggestions for improvement below...
> 
> > --- a/drivers/net/can/rcar/rcar_canfd.c
> > +++ b/drivers/net/can/rcar/rcar_canfd.c
> > @@ -109,16 +109,7 @@
> >  #define RCANFD_CFG_BRP_MASK            GENMASK(9, 0)
> >
> >  /* RSCFDnCFDCmNCFG - CAN FD only */
> > -#define RCANFD_NCFG_NTSEG2(gpriv, x) \
> > -       (((x) & ((gpriv)->info->nom_bittiming->tseg2_max - 1)) << (gpriv)->info->sh->ntseg2)
> > -
> > -#define RCANFD_NCFG_NTSEG1(gpriv, x) \
> > -       (((x) & ((gpriv)->info->nom_bittiming->tseg1_max - 1)) << (gpriv)->info->sh->ntseg1)
> > -
> > -#define RCANFD_NCFG_NSJW(gpriv, x) \
> > -       (((x) & ((gpriv)->info->nom_bittiming->sjw_max - 1)) << (gpriv)->info->sh->nsjw)
> > -
> > -#define RCANFD_NCFG_NBRP(x)            (((x) & 0x3ff) << 0)
> > +#define RCANFD_NCFG_NBRP_MASK          GENMASK(9, 0)
> 
> I would drop the "_MASK" suffix.

Agreed.

> 
> > @@ -1393,6 +1384,28 @@ static irqreturn_t rcar_canfd_channel_interrupt(int irq, void *dev_id)
> >         return IRQ_HANDLED;
> >  }
> >
> > +static inline u32 rcar_canfd_compute_nominal_bit_rate_cfg(struct rcar_canfd_channel *priv,
> > +                                                         u16 tseg1,
> > +u16 brp, u16 sjw, u16 tseg2)
> 
> Perhaps follow the order as used in struct can_bittiming{_const}?
> I.e. tseg1, tseg2, sjw, brp.

Will reorder in next version.

> 
> > +{
> > +       struct rcar_canfd_global *gpriv = priv->gpriv;
> > +       const struct rcar_canfd_hw_info *info = gpriv->info;
> > +       u32 ntseg2, ntseg1, nsjw, nbrp;
> > +
> > +       if ((priv->can.ctrlmode & CAN_CTRLMODE_FD) || gpriv->info->shared_can_regs) {
> > +               ntseg2 = (tseg2 & (info->nom_bittiming->tseg2_max - 1)) << info->sh->ntseg2;
> > +               ntseg1 = (tseg1 & (info->nom_bittiming->tseg1_max - 1)) << info->sh->ntseg1;
> > +               nsjw = (sjw & (info->nom_bittiming->sjw_max - 1)) << info->sh->nsjw;
> > +               nbrp = FIELD_PREP(RCANFD_NCFG_NBRP_MASK, brp);
> 
> Perhaps use the order of the function parameters?

Agreed.

> 
> > +       } else {
> > +               ntseg2 = FIELD_PREP(RCANFD_CFG_TSEG2_MASK, tseg2);
> > +               ntseg1 = FIELD_PREP(RCANFD_CFG_TSEG1_MASK, tseg1);
> > +               nsjw = FIELD_PREP(RCANFD_CFG_SJW_MASK, sjw);
> > +               nbrp = FIELD_PREP(RCANFD_CFG_BRP_MASK, brp);
> 
> Likewise.

OK.

> 
> > +       }
> > +
> > +       return (ntseg1 | nbrp | nsjw | ntseg2);
> 
> Likewise.

Agreed.

Cheers,
Biju