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Message-ID: <58e17135b41da7eba8afd5d8fb5f25bcaffa7288.camel@gmail.com>
Subject: Re: [PATCH v2] drivers: hwmon: max31827: Add PEC support
From: Nuno =?ISO-8859-1?Q?S=E1?= <noname.nuno@gmail.com>
To: Guenter Roeck <linux@roeck-us.net>, Radu Sabau <radu.sabau@analog.com>
Cc: Jean Delvare <jdelvare@suse.com>, Jonathan Corbet <corbet@lwn.net>, 
	linux-hwmon@vger.kernel.org, linux-doc@vger.kernel.org, 
	linux-kernel@vger.kernel.org
Date: Fri, 24 May 2024 09:00:13 +0200
In-Reply-To: <e52a86de-ead6-40d3-b652-461a90bd5942@roeck-us.net>
References: <20240523121057.5689-1-radu.sabau@analog.com>
	 <e52a86de-ead6-40d3-b652-461a90bd5942@roeck-us.net>
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On Thu, 2024-05-23 at 07:19 -0700, Guenter Roeck wrote:
> On Thu, May 23, 2024 at 03:10:56PM +0300, Radu Sabau wrote:
> > Add support for PEC by attaching PEC attribute to the i2c device.
> > Add pec_store and pec_show function for accesing the "pec" file.
> >=20
> > Signed-off-by: Radu Sabau <radu.sabau@analog.com>
> > ---
>=20
> Change log missing.
>=20
> > =C2=A0Documentation/hwmon/max31827.rst | 13 +++++--
> > =C2=A0drivers/hwmon/max31827.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0 | 64 ++++++++++++++++++++++++++++++++
> > =C2=A02 files changed, 74 insertions(+), 3 deletions(-)
> >=20
> > diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max=
31827.rst
> > index 44ab9dc064cb..9c11a9518c67 100644
> > --- a/Documentation/hwmon/max31827.rst
> > +++ b/Documentation/hwmon/max31827.rst
> > @@ -131,7 +131,14 @@ The Fault Queue bits select how many consecutive t=
emperature
> > faults must occur
> > =C2=A0before overtemperature or undertemperature faults are indicated i=
n the
> > =C2=A0corresponding status bits.
> > =C2=A0
> > -Notes
> > ------
> > +PEC Support
> > +-----------
> > +
> > +When reading a register value, the PEC byte is computed and sent by th=
e chip.
> > +
> > +PEC on word data transaction respresents a signifcant increase in band=
witdh
> > +usage (+33% for both write and reads) in normal conditions.
> > =C2=A0
> > -PEC is not implemented.
> > +Since this operation implies there will be an extra delay to each
> > +transaction, PEC can be disabled or enabled through sysfs.
> > +Just write 1=C2=A0 to the "pec" file for enabling PEC and 0 for disabl=
ing it.
> > diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
> > index f8a13b30f100..e86f8890ee72 100644
> > --- a/drivers/hwmon/max31827.c
> > +++ b/drivers/hwmon/max31827.c
> > @@ -24,6 +24,7 @@
> > =C2=A0
> > =C2=A0#define MAX31827_CONFIGURATION_1SHOT_MASK	BIT(0)
> > =C2=A0#define MAX31827_CONFIGURATION_CNV_RATE_MASK	GENMASK(3, 1)
> > +#define MAX31827_CONFIGURATION_PEC_EN_MASK	BIT(4)
> > =C2=A0#define MAX31827_CONFIGURATION_TIMEOUT_MASK	BIT(5)
> > =C2=A0#define MAX31827_CONFIGURATION_RESOLUTION_MASK	GENMASK(7, 6)
> > =C2=A0#define MAX31827_CONFIGURATION_ALRM_POL_MASK	BIT(8)
> > @@ -475,6 +476,54 @@ static ssize_t temp1_resolution_store(struct devic=
e *dev,
> > =C2=A0
> > =C2=A0static DEVICE_ATTR_RW(temp1_resolution);
> > =C2=A0
> > +static ssize_t pec_show(struct device *dev, struct device_attribute *d=
evattr,
> > +			char *buf)
> > +{
> > +	struct i2c_client *client =3D to_i2c_client(dev);
> > +
> > +	return scnprintf(buf, PAGE_SIZE, "%d\n", !!(client->flags &
> > I2C_CLIENT_PEC));
> > +}
> > +
> > +static ssize_t pec_store(struct device *dev, struct device_attribute *=
devattr,
> > +			 const char *buf, size_t count)
> > +{
> > +	struct max31827_state *st =3D dev_get_drvdata(dev);
> > +	struct i2c_client *client =3D to_i2c_client(dev);
> > +	unsigned int val;
> > +	int err;
> > +
> > +	err =3D kstrtouint(buf, 10, &val);
> > +	if (err < 0)
> > +		return err;
> > +
> > +	switch (val) {
> > +	case 0:
> > +		err =3D regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
> > +					 MAX31827_CONFIGURATION_PEC_EN_MASK,
> > +					 val);
>=20
> While correct, this is misleading. Should write 0.
>=20
> > +		if (err)
> > +			return err;
> > +
> > +		client->flags &=3D ~I2C_CLIENT_PEC;
> > +		break;
> > +	case 1:
> > +		err =3D regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
> > +					 MAX31827_CONFIGURATION_PEC_EN_MASK,
> > +					 val);
>=20
> This is wrong. s/val/MAX31827_CONFIGURATION_PEC_EN_MASK/
>=20
>=20

Then, maybe use regmap_set_bits()...

- Nuno S=C3=A1