Re: [PATCH v3 10/15] can: grcan: Add saving and restoring of CAN FD baud-rate registers

[Arun Muthusamy]

On 1/23/26 15:00, Marc Kleine-Budde wrote:
> On 22.01.2026 13:10:33, Arun Muthusamy wrote:
> > From: Daniel Hellstrom <daniel@xxxxxxxxxxx>
> >
> > While reset the GRCAN baud-rates are preserved, since GRCANFD has the
> > baud-rate in different registers we need to add saving of those
> > registers too.
> >
> > Signed-off-by: Daniel Hellstrom <daniel@xxxxxxxxxxx>
> > Signed-off-by: Arun Muthusamy <arun.muthusamy@xxxxxxxxxxx>
> > ---
> >   drivers/net/can/grcan.c | 12 ++++++++++++
> >   1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/net/can/grcan.c b/drivers/net/can/grcan.c
> > index a2a5a5c868ff..0ee6e9bfbe7f 100644
> > --- a/drivers/net/can/grcan.c
> > +++ b/drivers/net/can/grcan.c
> > @@ -517,15 +517,27 @@ static void grcan_reset(struct net_device *dev)
> >   	struct grcan_priv *priv = netdev_priv(dev);
> >   	struct grcan_registers __iomem *regs = priv->regs;
> >   	u32 config = grcan_read_reg(&regs->conf);
> > +	u32 nbtr, fdbtr;
> > +
> > +	if (priv->hwcap->fd) {
> > +		nbtr = grcan_read_reg(&regs->nbtr);
> Why do you save nbtr....

You’re right. nbtr is reprogrammed by set_bittiming() after reset, so saving/restoring nbtr is redundant.

> > +		fdbtr = grcan_read_reg(&regs->fdbtr);
>     Who writes fdbtr in the first place?

These configuration values are embedded into the CAN controller IP at SoC design time(cfg record).
From the driver's standpoint, saving/restoring fdbtr also redundant.

--
BR,

Arun Muthusamy
Software Engineer
Frontgrade Gaisler
T : +46 (0) 700 558 528
arun.muthusamy@xxxxxxxxxxx

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