netdev - RE: [PATCH 6/6] can: sja1000: Add support for RZ/N1 SJA1000 CAN Controller

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Date:   Sun, 3 Jul 2022 07:15:16 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
CC:     Wolfgang Grandegger <wg@...ndegger.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "ukl@...gutronix.de" <ukl@...gutronix.de>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 6/6] can: sja1000: Add support for RZ/N1 SJA1000 CAN
 Controller

Hi Marc and Uwe,

> Subject: Re: [PATCH 6/6] can: sja1000: Add support for RZ/N1 SJA1000 CAN
> Controller
> 
> On 02.07.2022 15:01:30, Biju Das wrote:
> > The SJA1000 CAN controller on RZ/N1 SoC has some differences compared
> > to others like it has no clock divider register (CDR) support and it
> > has no HW loopback(HW doesn't see tx messages on rx).
> >
> > This patch adds support for RZ/N1 SJA1000 CAN Controller.
> >
> > Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> > ---
> >  drivers/net/can/sja1000/sja1000_platform.c | 34
> > ++++++++++++++++++----
> >  1 file changed, 29 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/net/can/sja1000/sja1000_platform.c
> > b/drivers/net/can/sja1000/sja1000_platform.c
> > index 5f3d362e0da5..8e63af76a013 100644
> > --- a/drivers/net/can/sja1000/sja1000_platform.c
> > +++ b/drivers/net/can/sja1000/sja1000_platform.c
> [...]
> > @@ -262,6 +276,16 @@ static int sp_probe(struct platform_device *pdev)
> >  	priv->reg_base = addr;
> >
> >  	if (of) {
> > +		clk = devm_clk_get_optional(&pdev->dev, "can_clk");
> > +		if (IS_ERR(clk))
> > +			return dev_err_probe(&pdev->dev, PTR_ERR(clk), "no CAN
> clk");
> > +
> > +		if (clk) {
> > +			priv->can.clock.freq  = clk_get_rate(clk) / 2;
> > +			if (!priv->can.clock.freq)
> > +				return dev_err_probe(&pdev->dev, -EINVAL, "Zero
> CAN clk rate");
> > +		}
> 
> There's no clk_prepare_enable in the driver. You might go the quick and
> dirty way an enable the clock right here. IIRC there's a new convenience
> function to get and enable a clock, managed bei devm. Uwe (Cc'ed) can
> point you in the right direction.

 + clk

As per the patch history devm version for clk_prepare_enable is rejected[1], so the individual drivers implemented the same using devm_add_action_or_reset [2].
So shall I implement devm version here as well?

[1]https://lkml.iu.edu/hypermail/linux/kernel/2103.1/01556.html

[2] https://elixir.bootlin.com/linux/v5.19-rc4/source/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c#L266

Cheers,
Biju