linux-kernel - Re: [PATCH v2 1/2] can: tcan4x5x: add option for selecting nWKRQ voltage

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Message-ID: <20241114-rebel-peach-rhino-96357c-mkl@pengutronix.de>
Date: Thu, 14 Nov 2024 10:05:17 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Vincent Mailhol <mailhol.vincent@...adoo.fr>
Cc: Sean Nyekjaer <sean@...nix.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, linux-can@...r.kernel.org, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/2] can: tcan4x5x: add option for selecting nWKRQ
 voltage

On 14.11.2024 13:53:34, Vincent Mailhol wrote:
> On Mon. 11 Nov. 2024 at 17:55, Sean Nyekjaer <sean@...nix.com> wrote:
> > nWKRQ supports an output voltage of either the internal reference voltage
> > (3.6V) or the reference voltage of the digital interface 0 - 6V.
> > Add the devicetree option ti,nwkrq-voltage-sel to be able to select
> > between them.
> > Default is kept as the internal reference voltage.
> >
> > Signed-off-by: Sean Nyekjaer <sean@...nix.com>
> > ---
> >  drivers/net/can/m_can/tcan4x5x-core.c | 35 +++++++++++++++++++++++++++++++++++
> >  drivers/net/can/m_can/tcan4x5x.h      |  2 ++
> >  2 files changed, 37 insertions(+)
> >
> > diff --git a/drivers/net/can/m_can/tcan4x5x-core.c b/drivers/net/can/m_can/tcan4x5x-core.c
> > index 2f73bf3abad889c222f15c39a3d43de1a1cf5fbb..264bba830be50033347056da994102f8b614e51b 100644
> > --- a/drivers/net/can/m_can/tcan4x5x-core.c
> > +++ b/drivers/net/can/m_can/tcan4x5x-core.c
> > @@ -92,6 +92,8 @@
> >  #define TCAN4X5X_MODE_STANDBY BIT(6)
> >  #define TCAN4X5X_MODE_NORMAL BIT(7)
> >
> > +#define TCAN4X5X_NWKRQ_VOLTAGE_MASK BIT(19)
> > +
> >  #define TCAN4X5X_DISABLE_WAKE_MSK      (BIT(31) | BIT(30))
> >  #define TCAN4X5X_DISABLE_INH_MSK       BIT(9)
> >
> > @@ -267,6 +269,11 @@ static int tcan4x5x_init(struct m_can_classdev *cdev)
> >         if (ret)
> >                 return ret;
> >
> > +       ret = regmap_update_bits(tcan4x5x->regmap, TCAN4X5X_CONFIG,
> > +                                TCAN4X5X_NWKRQ_VOLTAGE_MASK, tcan4x5x->nwkrq_voltage);
> > +       if (ret)
> > +               return ret;
> > +
> >         return ret;
> >  }
> >
> > @@ -318,6 +325,28 @@ static const struct tcan4x5x_version_info
> >         return &tcan4x5x_versions[TCAN4X5X];
> >  }
> >
> > +static int tcan4x5x_get_dt_data(struct m_can_classdev *cdev)
> > +{
> > +       struct tcan4x5x_priv *tcan4x5x = cdev_to_priv(cdev);
> > +       struct device_node *np = cdev->dev->of_node;
> > +       u8 prop;
> > +       int ret;
> > +
> > +       ret = of_property_read_u8(np, "ti,nwkrq-voltage-sel", &prop);
> > +       if (!ret) {
> > +               if (prop <= 1)
> > +                       tcan4x5x->nwkrq_voltage = prop;
> > +               else
> > +                       dev_warn(cdev->dev,
> > +                                "nwkrq-voltage-sel have invalid option: %u\n",
> > +                                prop);
> > +       } else {
> > +               tcan4x5x->nwkrq_voltage = 0;
> > +       }
> 
> If the
> 
>   if (prop <= 1)
> 
> condition fails, you print a warning, but you are not assigning a
> value to tcan4x5x->nwkrq_voltage. Is this intentional?
> 
> What about:
> 
>         tcan4x5x->nwkrq_voltage = 0;
>         ret = of_property_read_u8(np, "ti,nwkrq-voltage-sel", &prop);
>         if (!ret) {
>                 if (prop <= 1)
>                         tcan4x5x->nwkrq_voltage = prop;
>                 else
>                         dev_warn(cdev->dev,
>                                  "nwkrq-voltage-sel have invalid option: %u\n",
>                                  prop);
>         }
> 
> so that you make sure that tcan4x5x->nwkrq_voltage always gets a
> default zero value? Else, if you can make sure that tcan4x5x is always
> zero initialized, you can just drop the

The tcan4x5x_priv is allocated in the netdev priv, which is initialized
with 0x0.

> 
>         tcan4x5x->nwkrq_voltage = 0;
> 
> thing.

regards,
Marc

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