Re: [PATCH 2/3] hwmon: Support ADI Fan Control IP

["Sa, Nuno" <Nuno.Sa@analog.com>]

On Sun, 2019-10-06 at 08:32 -0700, Guenter Roeck wrote:
> 
> On Thu, Sep 26, 2019 at 12:39:24PM +0200, Nuno Sá wrote:
> > The purpose of this IP Core is to control the fan used for the
> > cooling of a
> > Xilinx Zynq Ultrascale+ MPSoC without the need of any external
> > temperature
> > sensors. To achieve this, the IP core uses the PL SYSMONE4
> > primitive to
> > obtain the PL temperature and, based on those readings, it then
> > outputs
> > a PWM signal to control the fan rotation accordingly.
> > 
> > Signed-off-by: Nuno Sá <nuno.sa@analog.com>
> > ---
> >  MAINTAINERS                     |   7 +
> >  drivers/hwmon/Kconfig           |   9 +
> >  drivers/hwmon/Makefile          |   1 +
> >  drivers/hwmon/axi-fan-control.c | 452
> > ++++++++++++++++++++++++++++++++
> >  4 files changed, 469 insertions(+)
> >  create mode 100644 drivers/hwmon/axi-fan-control.c
> > 
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index c7035ce2460b..d775c923d23b 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -2853,6 +2853,13 @@ S:	Maintained
> >  F:	Documentation/devicetree/bindings/sound/axentia,*
> >  F:	sound/soc/atmel/tse850-pcm5142.c
> >  
> > +AXI-FAN-CONTROL HARDWARE MONITOR DRIVER
> > +M:	Nuno Sá <nuno.sa@analog.com>
> > +W:	http://ez.analog.com/community/linux-device-drivers
> > +L:	linux-hwmon@vger.kernel.org
> > +S:	Supported
> > +F:	drivers/hwmon/axi-fan-control.c
> > +
> >  AXXIA I2C CONTROLLER
> >  M:	Krzysztof Adamski <krzysztof.adamski@nokia.com>
> >  L:	linux-i2c@vger.kernel.org
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 2ca5668bdb62..2396cc347c47 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -269,6 +269,15 @@ config SENSORS_ASC7621
> >  	  This driver can also be built as a module. If so, the module
> >  	  will be called asc7621.
> >  
> > +config SENSORS_AXI_FAN_CONTROL
> > +	tristate "Analog Devices FAN Control HDL Core driver"
> > +	help
> > +	  If you say yes here you get support for the Analog Devices
> > +	  AXI HDL FAN monitoring core.
> > +
> > +	  This driver can also be built as a module. If so, the module
> > +	  will be called axi-fan-control
> > +
> >  config SENSORS_K8TEMP
> >  	tristate "AMD Athlon64/FX or Opteron temperature sensor"
> >  	depends on X86 && PCI
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index c86ce4d3d36b..ebb1fd2ea82b 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -51,6 +51,7 @@ obj-$(CONFIG_SENSORS_AS370)	+= as370-
> > hwmon.o
> >  obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
> >  obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o
> >  obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
> > +obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o
> >  obj-$(CONFIG_SENSORS_CORETEMP)	+= coretemp.o
> >  obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
> >  obj-$(CONFIG_SENSORS_DA9055)+= da9055-hwmon.o
> > diff --git a/drivers/hwmon/axi-fan-control.c b/drivers/hwmon/axi-
> > fan-control.c
> > new file mode 100644
> > index 000000000000..f86efc444753
> > --- /dev/null
> > +++ b/drivers/hwmon/axi-fan-control.c
> > @@ -0,0 +1,452 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Fan Control HDL CORE driver
> > + *
> > + * Copyright 2019 Analog Devices Inc.
> > + */
> > +#include <linux/clk.h>
> > +#include <linux/fpga/adi-axi-common.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/io.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +
> > +/* register map */
> > +#define ADI_REG_RSTN		0x0080
> > +#define ADI_REG_PWM_WIDTH	0x0084
> > +#define ADI_REG_TACH_PERIOD	0x0088
> > +#define ADI_REG_TACH_TOLERANCE	0x008c
> > +#define ADI_REG_PWM_PERIOD	0x00c0
> > +#define ADI_REG_TACH_MEASUR	0x00c4
> > +#define ADI_REG_TEMPERATURE	0x00c8
> > +
> > +#define ADI_REG_IRQ_MASK	0x0040
> > +#define ADI_REG_IRQ_PENDING	0x0044
> > +#define ADI_REG_IRQ_SRC		0x0048
> > +
> > +/* IRQ sources */
> > +#define ADI_IRQ_SRC_PWM_CHANGED		BIT(0)
> 
> include linux/bits.h

ack.

> > +#define ADI_IRQ_SRC_TACH_ERR		BIT(1)
> > +#define ADI_IRQ_SRC_TEMP_INCREASE	BIT(2)
> > +#define ADI_IRQ_SRC_NEW_MEASUR		BIT(3)
> > +#define ADI_IRQ_SRC_MASK		GENMASK(3, 0)
> > +#define ADI_IRQ_MASK_OUT_ALL		0xFFFFFFFFU
> > +
> > +#define SYSFS_PWM_MAX			255
> > +
> > +struct axi_fan_control_data {
> > +	struct clk *clk;
> > +	void __iomem *base;
> > +	/* tacho period */
> > +	atomic_t tach;
> 
> Why exactly is this an atomic ? The value is only set, and it is set
> in
> a single operation. Why does it matter if reqading it catches the old
> or
> the new value ?

Hmm, I think that I don't even need this variable. I can just ioread
the value when getting the fan rpm and get whatever it is on the
register at that moment.
  
> > +	int irq;
> > +	/* pulses per revolution */
> > +	u32 ppr;
> > +	bool hw_pwm_req;
> > +	bool update_tacho_params;
> > +	u8 fan_fault;
> > +};
> > +
> > +static inline void axi_fan_control_iowrite(const u32 val, const
> > u32 reg,
> > +				const struct axi_fan_control_data *ctl)
> 
> Multi-line alignment. Also, please consider shorter function names.
> An "axi_fan_control_" prefix for static functions is really a bit
> excessive
> and doesn't add value. "axi_" would do it just as well.

Will do that.

> > +{
> > +	iowrite32(val, ctl->base + reg);
> > +}
> > +
> > +static inline u32 axi_fan_control_ioread(const u32 reg,
> > +					 const struct
> > axi_fan_control_data *ctl)
> > +{
> > +	return ioread32(ctl->base + reg);
> > +}
> > +
> > +static long axi_fan_control_get_pwm_duty(const struct
> > axi_fan_control_data *ctl)
> > +{
> > +	u32 pwm_width = axi_fan_control_ioread(ADI_REG_PWM_WIDTH, ctl);
> > +	u32 pwm_period = axi_fan_control_ioread(ADI_REG_PWM_PERIOD,
> > ctl);
> > +
> > +	return DIV_ROUND_CLOSEST(pwm_width * SYSFS_PWM_MAX,
> > pwm_period);
> 
> Is pwm_period guaranteed to be != 0 ?

Yes, It is a RO register and it is set by the core with the default of
0x4e20.
> > +}
> > +
> > +static int axi_fan_control_set_pwm_duty(const long val,
> > +					struct axi_fan_control_data
> > *ctl)
> > +{
> > +	u32 pwm_period = axi_fan_control_ioread(ADI_REG_PWM_PERIOD,
> > ctl);
> > +	u32 new_width;
> > +	long __val = clamp_val(val, 0, SYSFS_PWM_MAX);
> > +
> > +	new_width = DIV_ROUND_CLOSEST(__val * pwm_period,
> > SYSFS_PWM_MAX);
> > +
> > +	axi_fan_control_iowrite(new_width, ADI_REG_PWM_WIDTH, ctl);
> > +
> > +	return 0;
> > +}
> > +
> > +static long axi_fan_control_get_fan_rpm(const struct
> > axi_fan_control_data *ctl)
> > +{
> > +	unsigned long clk_rate = clk_get_rate(ctl->clk);
> > +
> > +	if (!clk_rate)
> > +		return -EINVAL;
> 
> Unless the clock rate changes dynamically, it might make sense to
> read it once
> in the probe function.

Hmm, It can't so I will do as you suggest.

> > +	/*
> > +	 * The tacho period should be:
> > +	 *      TACH = 60/(ppr * rpm), where rpm is revolutions per
> > second
> > +	 *      and ppr is pulses per revolution.
> > +	 * Given the tacho period, we can multiply it by the input
> > clock
> > +	 * so that we know how many clocks we need to have this period.
> > +	 * From this, we can derive the RPM value.
> > +	 */
> > +	return DIV_ROUND_CLOSEST(60 * clk_rate,
> > +				 ctl->ppr * atomic_read(&ctl->tach));
> 
> Are ppr and tach guaranteed to be != 0 ? I don't think so,
> since neither is ever evaluated.

Nope. I should make sure ppr is never 0 and I shoud evaluate tach
before  doing the operation and return 0 
> > +}
> > +
> > +static int axi_fan_control_read_temp(struct device *dev, u32 attr,
> > long *val)
> > +{
> > +	struct axi_fan_control_data *ctl = dev_get_drvdata(dev);
> > +	long raw_temp;
> > +
> > +	switch (attr) {
> > +	case hwmon_temp_input:
> > +		raw_temp = axi_fan_control_ioread(ADI_REG_TEMPERATURE,
> > ctl);
> > +		/*
> > +		 * The formula for the temperature is:
> > +		 *      T = (ADC * 501.3743 / 2^bits) - 273.6777
> > +		 * It's multiplied by 1000 to have milidegrees as
> 
> s/milidegrees/millidegrees/

ack.

> > +		 * specified by the hwmon sysfs interface.
> > +		 */
> > +		*val = ((raw_temp * 501374) >> 16) - 273677;
> > +		return 0;
> > +	default:
> > +		return -ENOTSUPP;
> > +	}
> > +}
> > +
> > +static int axi_fan_control_read_fan(struct device *dev, u32 attr,
> > long *val)
> > +{
> > +	struct axi_fan_control_data *ctl = dev_get_drvdata(dev);
> > +
> > +	switch (attr) {
> > +	case hwmon_fan_fault:
> > +		*val = ctl->fan_fault;
> > +		return 0;
> > +	case hwmon_fan_input:
> > +		*val = axi_fan_control_get_fan_rpm(ctl);
> > +		return 0;
> > +	default:
> > +		return -ENOTSUPP;
> > +	}
> > +}
> > +
> > +static int axi_fan_control_read_pwm(struct device *dev, u32 attr,
> > long *val)
> > +{
> > +	struct axi_fan_control_data *ctl = dev_get_drvdata(dev);
> > +
> > +	switch (attr) {
> > +	case hwmon_pwm_input:
> > +		*val = axi_fan_control_get_pwm_duty(ctl);
> > +		return 0;
> > +	default:
> > +		return -ENOTSUPP;
> > +	}
> > +}
> > +
> > +static int axi_fan_control_write_pwm(struct device *dev, u32 attr,
> > long val)
> > +{
> > +	struct axi_fan_control_data *ctl = dev_get_drvdata(dev);
> > +
> > +	switch (attr) {
> > +	case hwmon_pwm_input:
> > +		return axi_fan_control_set_pwm_duty(val, ctl);
> > +	default:
> > +		return -ENOTSUPP;
> > +	}
> > +}
> > +
> > +static int axi_fan_control_read_labels(struct device *dev,
> > +				       enum hwmon_sensor_types type,
> > +				       u32 attr, int channel, const
> > char **str)
> > +{
> > +	switch (type) {
> > +	case hwmon_fan:
> > +		*str = "FAN";
> > +		return 0;
> > +	case hwmon_temp:
> > +		*str = "SYSMON4";
> > +		return 0;
> > +	default:
> > +		return -ENOTSUPP;
> > +	}
> > +}
> > +
> > +static int axi_fan_control_read(struct device *dev,
> > +				enum hwmon_sensor_types type,
> > +				u32 attr, int channel, long *val)
> > +{
> > +	switch (type) {
> > +	case hwmon_fan:
> > +		return axi_fan_control_read_fan(dev, attr, val);
> > +	case hwmon_pwm:
> > +		return axi_fan_control_read_pwm(dev, attr, val);
> > +	case hwmon_temp:
> > +		return axi_fan_control_read_temp(dev, attr, val);
> > +	default:
> > +		return -ENOTSUPP;
> > +	}
> > +}
> > +
> > +static int axi_fan_control_write(struct device *dev,
> > +				 enum hwmon_sensor_types type,
> > +				 u32 attr, int channel, long val)
> > +{
> > +	switch (type) {
> > +	case hwmon_pwm:
> > +		return axi_fan_control_write_pwm(dev, attr, val);
> > +	default:
> > +		return -ENOTSUPP;
> > +	}
> > +}
> > +
> > +static umode_t axi_fan_control_fan_is_visible(const u32 attr)
> > +{
> > +	switch (attr) {
> > +	case hwmon_fan_input:
> > +	case hwmon_fan_fault:
> > +	case hwmon_fan_label:
> > +		return 0444;
> > +	default:
> > +		return 0;
> > +	}
> > +}
> > +
> > +static umode_t axi_fan_control_pwm_is_visible(const u32 attr)
> > +{
> > +	switch (attr) {
> > +	case hwmon_pwm_input:
> > +		return 0644;
> > +	default:
> > +		return 0;
> > +	}
> > +}
> > +
> > +static umode_t axi_fan_control_temp_is_visible(const u32 attr)
> > +{
> > +	switch (attr) {
> > +	case hwmon_temp_input:
> > +	case hwmon_temp_label:
> > +		return 0444;
> > +	default:
> > +		return 0;
> > +	}
> > +}
> > +
> > +static umode_t axi_fan_control_is_visible(const void *data,
> > +					  enum hwmon_sensor_types type,
> > +					  u32 attr, int channel)
> > +{
> > +	switch (type) {
> > +	case hwmon_fan:
> > +		return axi_fan_control_fan_is_visible(attr);
> > +	case hwmon_pwm:
> > +		return axi_fan_control_pwm_is_visible(attr);
> > +	case hwmon_temp:
> > +		return axi_fan_control_temp_is_visible(attr);
> > +	default:
> > +		return 0;
> > +	}
> > +}
> > +
> > +static irqreturn_t axi_fan_control_irq_handler(int irq, void
> > *data)
> > +{
> > +	struct axi_fan_control_data *ctl = (struct axi_fan_control_data
> > *)data;
> > +	u32 irq_pending = axi_fan_control_ioread(ADI_REG_IRQ_PENDING,
> > ctl);
> > +	u32 clear_mask;
> > +
> > +	if (irq_pending & ADI_IRQ_SRC_NEW_MEASUR) {
> > +		u32 new_tach =
> > axi_fan_control_ioread(ADI_REG_TACH_MEASUR,
> > +						      ctl);
> > +
> > +		if (ctl->update_tacho_params) {
> > +			/* get 25% tolerance */
> > +			u32 tach_tol = DIV_ROUND_CLOSEST(new_tach * 25,
> > 100);
> > +			/* set new tacho parameters */
> > +			axi_fan_control_iowrite(new_tach,
> > ADI_REG_TACH_PERIOD,
> > +						ctl);
> > +			axi_fan_control_iowrite(tach_tol,
> > +						ADI_REG_TACH_TOLERANCE,
> > ctl);
> > +			ctl->update_tacho_params = false;
> > +		}
> > +
> > +		atomic_set(&ctl->tach, new_tach);
> > +	}
> > +
> > +	if (irq_pending & ADI_IRQ_SRC_PWM_CHANGED) {
> > +		/*
> > +		 * if the pwm changes on behalf of software,
> > +		 * we need to provide new tacho parameters to the core.
> > +		 * Wait for the next measurement for that...
> > +		 */
> > +		if (!ctl->hw_pwm_req)
> > +			ctl->update_tacho_params = true;
> > +
> > +		/* just set this to false even if it is already... */
> > +		ctl->hw_pwm_req = false;
> > +	}
> > +
> > +	if (irq_pending & ADI_IRQ_SRC_TEMP_INCREASE)
> > +		/* hardware requested a new pwm */
> > +		ctl->hw_pwm_req = true;
> > +
> I don't really understand the logic here. If
> ADI_IRQ_SRC_TEMP_INCREASE means
> that hardware wants a new pwm, how is userspace informed about that
> request ?

It isn't. Userspace would have to read the pwm attribute and figure
that changed. Should I use something like sysfs_notify() on the pwm
attribute?

> And why are the tacho paramaters _not_ updated in this case later on
> (unless
> ADI_IRQ_SRC_PWM_CHANGED and ADI_IRQ_SRC_TEMP_INCREASE are both set) ?
> It might be useful to describe the expected sequence of events.

The core can change the PWM by itself (which is when we receive
ADI_IRQ_SRC_TEMP_INCREASE) and in that case it will use predefined
values to evaluate the tacho signal (so it won't use the values on
TACH_PERIOD and TACH_TOLERANCE). Alternatively, the user can request a
new PWM by writing the pwm attribute. In this case the CORE is
expecting that TACH_PERIOD and TACH_TOLERANCE are given otherwise it
won't evaluate the tacho signal. Note that when is the user which
requests a new pwm we only get ADI_IRQ_SRC_PWM_CHANGED (and not +	
if (irq_pending & ADI_IRQ_SRC_TEMP_INCREASE), so I use that to know
when do I have to update the tacho parameters.
 
> > 
)

> > +	if (irq_pending & ADI_IRQ_SRC_TACH_ERR)
> > +		ctl->fan_fault = 1;
> 
> Is it on purpose that this bit is never reset ?

Yes, and it is wrong. I though that the core would never clear this
alarm but it does clear it in the next temperature reading cycle (and
set it again if needed). Then, would a clear on read be a correct
approach?
> 
> > +
> > +	/* clear all interrupts */
> > +	clear_mask = irq_pending & ADI_IRQ_SRC_MASK;
> > +	axi_fan_control_iowrite(clear_mask, ADI_REG_IRQ_PENDING, ctl);
> > +
> > +	return IRQ_HANDLED;
> > +}
> > +
> > +static int axi_fan_control_init(struct axi_fan_control_data *ctl,
> > +				const struct device_node *np)
> > +{
> > +	int ret;
> > +
> > +	/* get fan pulses per revolution */
> > +	ret = of_property_read_u32(np, "adi,pulses-per-revolution",
> > &ctl->ppr);
> > +	if (ret)
> > +		return ret;
> 
> So all random values are acceptable, including 0 and 0xffffffff ?

Yes, I'm aware that 1 and 2 are typical values but I'm not sure what is
the maximum that typically exists so I didn't want to put limits here
without knowing. Though at least 0 must not be accepted since then we
are always dividing by 0 when reading the FAN rpm.

> > +	/*
> > +	 * Enable all IRQs
> > +	 */
> > +	axi_fan_control_iowrite((ADI_IRQ_MASK_OUT_ALL &
> > +			~(ADI_IRQ_SRC_NEW_MEASUR | ADI_IRQ_SRC_TACH_ERR
> > |
> > +			ADI_IRQ_SRC_PWM_CHANGED |
> > ADI_IRQ_SRC_TEMP_INCREASE)),
> 
> One set of ( ) is unnecessary.

ack.

> > +			ADI_REG_IRQ_MASK, ctl);
> > +
> > +	/* bring the device out of reset */
> > +	axi_fan_control_iowrite(0x01, ADI_REG_RSTN, ctl);
> > +
> > +	return ret;
> > +}
> > +
> > +static const struct hwmon_channel_info *axi_fan_control_info[] = {
> > +	HWMON_CHANNEL_INFO(pwm, HWMON_PWM_INPUT),
> > +	HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT | HWMON_F_FAULT |
> > HWMON_F_LABEL),
> > +	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_LABEL),
> > +	NULL
> > +};
> > +
> > +static const struct hwmon_ops axi_fan_control_hwmon_ops = {
> > +	.is_visible = axi_fan_control_is_visible,
> > +	.read = axi_fan_control_read,
> > +	.write = axi_fan_control_write,
> > +	.read_string = axi_fan_control_read_labels,
> > +};
> > +
> > +static const struct hwmon_chip_info axi_fan_control_chip_info = {
> > +	.ops = &axi_fan_control_hwmon_ops,
> > +	.info = axi_fan_control_info,
> > +};
> > +
> > +static const u32 version_1_0_0 = ADI_AXI_PCORE_VER(1, 0, 'a');
> > +
> > +static const struct of_device_id axi_fan_control_of_match[] = {
> > +	{ .compatible = "adi,axi-fan-control-1.00.a",
> > +		.data = (void *)&version_1_0_0},
> > +	{},
> > +};
> > +MODULE_DEVICE_TABLE(of, axi_fan_control_of_match);
> > +
> > +static int axi_fan_control_probe(struct platform_device *pdev)
> > +{
> > +	struct device *hwmon_dev;
> > +	struct axi_fan_control_data *ctl;
> > +	const struct of_device_id *id;
> > +	struct resource *res;
> > +	u32 version;
> > +	int ret;
> > +
> > +	id = of_match_node(axi_fan_control_of_match, pdev-
> > >dev.of_node);
> > +	if (!id)
> > +		return -EINVAL;
> > +
> > +	ctl = devm_kzalloc(&pdev->dev, sizeof(*ctl), GFP_KERNEL);
> > +	if (!ctl)
> > +		return -ENOMEM;
> > +
> > +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	ctl->base = devm_ioremap_resource(&pdev->dev, res);
> 
> devm_platform_ioremap_resource()

ack.

> > +	if (IS_ERR(ctl->base)) {
> > +		dev_err(&pdev->dev, "ioremap failed with %ld\n",
> > +			PTR_ERR(ctl->base));
> > +		return PTR_ERR(ctl->base);
> > +	}
> 
> This does not require an extra error message.

ack.

> > +
> > +	ctl->clk = devm_clk_get(&pdev->dev, NULL);
> > +	if (IS_ERR(ctl->clk)) {
> > +		dev_err(&pdev->dev, "clk_get failed with %ld\n",
> > +			PTR_ERR(ctl->clk));
> > +		return PTR_ERR(ctl->clk);
> > +	}
> > +
> > +	dev_dbg(&pdev->dev, "Re-mapped from 0x%08llX to %p\n",
> > +		(unsigned long long)res->start, ctl->base);
> > +
> > +	version = axi_fan_control_ioread(ADI_AXI_REG_VERSION, ctl);
> > +	if (ADI_AXI_PCORE_VER_MAJOR(version) !=
> > +	    ADI_AXI_PCORE_VER_MAJOR((*(u32 *)id->data))) {
> > +		dev_err(&pdev->dev, "Major version mismatch. Expected
> > %d.%.2d.%c, Reported %d.%.2d.%c\n",
> > +			ADI_AXI_PCORE_VER_MAJOR((*(u32 *)id->data)),
> > +			ADI_AXI_PCORE_VER_MINOR((*(u32 *)id->data)),
> > +			ADI_AXI_PCORE_VER_PATCH((*(u32 *)id->data)),
> > +			ADI_AXI_PCORE_VER_MAJOR(version),
> > +			ADI_AXI_PCORE_VER_MINOR(version),
> > +			ADI_AXI_PCORE_VER_PATCH(version));
> > +		return -ENODEV;
> > +	}
> > +
> > +	ctl->irq = platform_get_irq(pdev, 0);
> > +	if (ctl->irq < 0) {
> 
> This can return -EPROBE_DEFER. On top of that, it already generates
> an error
> message, meaning another one here is unnecessary.

ack.

> > +		dev_err(&pdev->dev, "platform_get_irq failed with
> > %d\n",
> > +			ctl->irq);
> > +		return ctl->irq;
> > +	}
> > +
> > +	ret = devm_request_threaded_irq(&pdev->dev, ctl->irq, NULL,
> > +					axi_fan_control_irq_handler,
> > +					IRQF_ONESHOT |
> > IRQF_TRIGGER_HIGH,
> > +					pdev->driver_override, ctl);
> > +	if (ret) {
> > +		dev_err(&pdev->dev, "failed to request an irq, %d",
> > ret);
> > +		return ret;
> > +	}
> > +
> > +	ret = axi_fan_control_init(ctl, pdev->dev.of_node);
> > +	if (ret) {
> > +		dev_err(&pdev->dev, "Failed to initialize device\n");
> > +		return ret;
> > +	}
> > +
> > +	hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
> > +						"axi_fan_control",
> > +						ctl,
> > +						&axi_fan_control_chip_i
> > nfo,
> > +						NULL);
> 
> Another alignment issue. Shorter function and global variable names
> would help.

ack.

> > +
> > +	return PTR_ERR_OR_ZERO(hwmon_dev);
> > +}
> > +
> > +static struct platform_driver axi_fan_control_driver = {
> > +	.driver = {
> > +		.name = "axi_fan_control_driver",
> > +		.of_match_table = axi_fan_control_of_match,
> > +	},
> > +	.probe = axi_fan_control_probe,
> > +};
> > +module_platform_driver(axi_fan_control_driver);
> > +
> > +MODULE_AUTHOR("Nuno Sa <nuno.sa@analog.com>");
> > +MODULE_DESCRIPTION("Analog Devices Fan Control HDL CORE driver");
> > +MODULE_LICENSE("GPL");
> > -- 
> > 2.23.0
> >