netdev - Re: [PATCH v3 3/6] can: sja1000: Add Quirk for RZ/N1 SJA1000 CAN controller

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Date:   Mon, 4 Jul 2022 18:54:54 +0900
From:   Vincent MAILHOL <mailhol.vincent@...adoo.fr>
To:     Biju Das <biju.das.jz@...renesas.com>
Cc:     Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Stefan Mätje <stefan.maetje@....eu>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        linux-can@...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
Subject: Re: [PATCH v3 3/6] can: sja1000: Add Quirk for RZ/N1 SJA1000 CAN controller

Hi Biju,

I gave a quick look to your series. Nothing odd to me, I just have a
single nitpick.

On Mon. 4 juil. 2022 at 16:51, Biju Das <biju.das.jz@...renesas.com> wrote:
> As per Chapter 6.5.16 of the RZ/N1 Peripheral Manual, The SJA1000
> CAN controller does not support Clock Divider Register compared to
> the reference Philips SJA1000 device.
>
> This patch adds a device quirk to handle this difference.
>
> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> ---
> v2->v3:
>  * No Change
> v1->v2:
>  * Updated commit description
>  * Removed the quirk macro SJA1000_NO_HW_LOOPBACK_QUIRK
>  * Added prefix SJA1000_QUIRK_* for quirk macro.
> ---
>  drivers/net/can/sja1000/sja1000.c | 13 ++++++++-----
>  drivers/net/can/sja1000/sja1000.h |  3 ++-
>  2 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/can/sja1000/sja1000.c b/drivers/net/can/sja1000/sja1000.c
> index 2e7638f98cf1..e9c55f5aa3c3 100644
> --- a/drivers/net/can/sja1000/sja1000.c
> +++ b/drivers/net/can/sja1000/sja1000.c
> @@ -183,8 +183,9 @@ static void chipset_init(struct net_device *dev)
>  {
>         struct sja1000_priv *priv = netdev_priv(dev);
>
> -       /* set clock divider and output control register */
> -       priv->write_reg(priv, SJA1000_CDR, priv->cdr | CDR_PELICAN);
> +       if (!(priv->flags & SJA1000_QUIRK_NO_CDR_REG))
> +               /* set clock divider and output control register */
> +               priv->write_reg(priv, SJA1000_CDR, priv->cdr | CDR_PELICAN);
>
>         /* set acceptance filter (accept all) */
>         priv->write_reg(priv, SJA1000_ACCC0, 0x00);
> @@ -208,9 +209,11 @@ static void sja1000_start(struct net_device *dev)
>         if (priv->can.state != CAN_STATE_STOPPED)
>                 set_reset_mode(dev);
>
> -       /* Initialize chip if uninitialized at this stage */
> -       if (!(priv->read_reg(priv, SJA1000_CDR) & CDR_PELICAN))
> -               chipset_init(dev);
> +       if (!(priv->flags & SJA1000_QUIRK_NO_CDR_REG)) {
> +               /* Initialize chip if uninitialized at this stage */
> +               if (!(priv->read_reg(priv, SJA1000_CDR) & CDR_PELICAN))

You can combine the two if in one:

|        /* Initialize chip if uninitialized at this stage */
|        if (!(priv->flags & SJA1000_QUIRK_NO_CDR_REG ||
|              priv->read_reg(priv, SJA1000_CDR) & CDR_PELICAN))
|                chipset_init(dev);

> +                       chipset_init(dev);
> +       }
>
>         /* Clear error counters and error code capture */
>         priv->write_reg(priv, SJA1000_TXERR, 0x0);
> diff --git a/drivers/net/can/sja1000/sja1000.h b/drivers/net/can/sja1000/sja1000.h
> index 9d46398f8154..7f736f1df547 100644
> --- a/drivers/net/can/sja1000/sja1000.h
> +++ b/drivers/net/can/sja1000/sja1000.h
> @@ -145,7 +145,8 @@
>  /*
>   * Flags for sja1000priv.flags
>   */
> -#define SJA1000_CUSTOM_IRQ_HANDLER 0x1
> +#define SJA1000_CUSTOM_IRQ_HANDLER     BIT(0)
> +#define SJA1000_QUIRK_NO_CDR_REG       BIT(1)
>
>  /*
>   * SJA1000 private data structure