[v4,5/5] hwmon: Add Aspeed ast2600 TACH support

  Add the support of Tachometer which can use to monitor the frequency of
the input. The tach supports up to 16 channels and it's part function of
multi-function device "pwm-tach controller".

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Reported-by: kernel test robot <lkp@intel.com>
---
 Documentation/hwmon/index.rst               |   1 +
 Documentation/hwmon/tach-aspeed-ast2600.rst |  24 ++
 drivers/hwmon/Kconfig                       |   9 +
 drivers/hwmon/Makefile                      |   1 +
 drivers/hwmon/tach-aspeed-ast2600.c         | 399 ++++++++++++++++++++
 5 files changed, 434 insertions(+)
 create mode 100644 Documentation/hwmon/tach-aspeed-ast2600.rst
 create mode 100644 drivers/hwmon/tach-aspeed-ast2600.c
  

On Wed, Nov 23, 2022 at 02:16:35PM +0800, Billy Tsai wrote:
> diff --git a/Documentation/hwmon/tach-aspeed-ast2600.rst b/Documentation/hwmon/tach-aspeed-ast2600.rst
> new file mode 100644
> index 000000000000..4f9501b783a1
> --- /dev/null
> +++ b/Documentation/hwmon/tach-aspeed-ast2600.rst
> @@ -0,0 +1,24 @@
> +Kernel driver tach-aspeed-ast2600
> +==============================
> +
> +Supported chips:
> +	ASPEED AST2600
> +
> +Authors:
> +	<billy_tsai@aspeedtech.com>
> +
> +Description:
> +------------
> +This driver implements support for ASPEED AST2600 Fan Tacho controller.
> +The controller supports up to 16 tachometer inputs.
> +
> +The driver provides the following sensor accesses in sysfs:
> +=============== ======= =====================================================
> +fanX_input	ro	provide current fan rotation value in RPM as reported
> +			by the fan to the device.
> +fanX_div	rw	Fan divisor: Supported value are power of 4 (1, 4, 16
> +                        64, ... 4194304)
> +                        The larger divisor, the less rpm accuracy and the less
> +                        affected by fan signal glitch.
> +fanX_pulses	rw      Fan pulses per resolution.
> +=============== ======= ======================================================

I found htmldocs warnings:

Documentation/hwmon/tach-aspeed-ast2600.rst:2: WARNING: Title underline too short.

Kernel driver tach-aspeed-ast2600
==============================
Documentation/hwmon/tach-aspeed-ast2600.rst:18: WARNING: Unexpected indentation.
Documentation/hwmon/tach-aspeed-ast2600.rst:19: WARNING: Block quote ends without a blank line; unexpected unindent.
Documentation/hwmon/tach-aspeed-ast2600.rst:23: WARNING: Definition list ends without a blank line; unexpected unindent.

I have applied the fixup:

---- >8 ----

diff --git a/Documentation/hwmon/tach-aspeed-ast2600.rst b/Documentation/hwmon/tach-aspeed-ast2600.rst
index 4f9501b783a11b..8faa00f6ad47c2 100644
--- a/Documentation/hwmon/tach-aspeed-ast2600.rst
+++ b/Documentation/hwmon/tach-aspeed-ast2600.rst
@@ -1,5 +1,5 @@
 Kernel driver tach-aspeed-ast2600
-==============================
+=================================
 
 Supported chips:
 	ASPEED AST2600
@@ -13,7 +13,8 @@ This driver implements support for ASPEED AST2600 Fan Tacho controller.
 The controller supports up to 16 tachometer inputs.
 
 The driver provides the following sensor accesses in sysfs:
-=============== ======= =====================================================
+
+=============== ======= ======================================================
 fanX_input	ro	provide current fan rotation value in RPM as reported
 			by the fan to the device.
 fanX_div	rw	Fan divisor: Supported value are power of 4 (1, 4, 16

Thanks.
  

On 11/22/22 22:16, Billy Tsai wrote:
> Add the support of Tachometer which can use to monitor the frequency of
> the input. The tach supports up to 16 channels and it's part function of
> multi-function device "pwm-tach controller".
> 
> Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
> Reported-by: kernel test robot <lkp@intel.com>

The above Reported-by: tag does not make sense for new drivers. Please drop.

Also, PATCH in subject is missing.

> ---
>   Documentation/hwmon/index.rst               |   1 +
>   Documentation/hwmon/tach-aspeed-ast2600.rst |  24 ++
>   drivers/hwmon/Kconfig                       |   9 +
>   drivers/hwmon/Makefile                      |   1 +
>   drivers/hwmon/tach-aspeed-ast2600.c         | 399 ++++++++++++++++++++
>   5 files changed, 434 insertions(+)
>   create mode 100644 Documentation/hwmon/tach-aspeed-ast2600.rst
>   create mode 100644 drivers/hwmon/tach-aspeed-ast2600.c
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index c1d11cf13eef..8aed4c42ca89 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -193,6 +193,7 @@ Hardware Monitoring Kernel Drivers
>      sparx5-temp
>      stpddc60
>      sy7636a-hwmon
> +   tach-aspeed-ast2600
>      tc654
>      tc74
>      thmc50
> diff --git a/Documentation/hwmon/tach-aspeed-ast2600.rst b/Documentation/hwmon/tach-aspeed-ast2600.rst
> new file mode 100644
> index 000000000000..4f9501b783a1
> --- /dev/null
> +++ b/Documentation/hwmon/tach-aspeed-ast2600.rst
> @@ -0,0 +1,24 @@
> +Kernel driver tach-aspeed-ast2600
> +==============================
> +
> +Supported chips:
> +	ASPEED AST2600
> +
> +Authors:
> +	<billy_tsai@aspeedtech.com>
> +
> +Description:
> +------------
> +This driver implements support for ASPEED AST2600 Fan Tacho controller.
> +The controller supports up to 16 tachometer inputs.
> +
> +The driver provides the following sensor accesses in sysfs:
> +=============== ======= =====================================================
> +fanX_input	ro	provide current fan rotation value in RPM as reported
> +			by the fan to the device.
> +fanX_div	rw	Fan divisor: Supported value are power of 4 (1, 4, 16
> +                        64, ... 4194304)

The code doesn't support 1.

> +                        The larger divisor, the less rpm accuracy and the less
> +                        affected by fan signal glitch.
> +fanX_pulses	rw      Fan pulses per resolution.
> +=============== ======= ======================================================
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 7ac3daaf59ce..3196087a7b3e 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -403,6 +403,15 @@ config SENSORS_ASPEED
>   	  This driver can also be built as a module. If so, the module
>   	  will be called aspeed_pwm_tacho.
>   
> +config SENSORS_TACH_ASPEED_AST2600
> +	tristate "ASPEED ast2600 Tachometer support"
> +	select REGMAP
> +	help
> +	  This driver provides support for Aspeed ast2600 Tachometer.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called tach-aspeed-ast2600.
> +
>   config SENSORS_ATXP1
>   	tristate "Attansic ATXP1 VID controller"
>   	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 11d076cad8a2..50a139c7c4ca 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -53,6 +53,7 @@ obj-$(CONFIG_SENSORS_ARM_SCMI)	+= scmi-hwmon.o
>   obj-$(CONFIG_SENSORS_ARM_SCPI)	+= scpi-hwmon.o
>   obj-$(CONFIG_SENSORS_AS370)	+= as370-hwmon.o
>   obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
> +obj-$(CONFIG_SENSORS_TACH_ASPEED_AST2600) += tach-aspeed-ast2600.o
>   obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o
>   obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
>   obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o
> diff --git a/drivers/hwmon/tach-aspeed-ast2600.c b/drivers/hwmon/tach-aspeed-ast2600.c
> new file mode 100644
> index 000000000000..2b8dd5eeb6ec
> --- /dev/null
> +++ b/drivers/hwmon/tach-aspeed-ast2600.c
> @@ -0,0 +1,399 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) ASPEED Technology Inc.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/errno.h>
> +#include <linux/hwmon.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/reset.h>
> +#include <linux/sysfs.h>
> +
> +/* The channel number of Aspeed tach controller */
> +#define TACH_ASPEED_NR_TACHS		16
> +/* TACH Control Register */
> +#define TACH_ASPEED_CTRL(ch)		(((ch) * 0x10) + 0x08)
> +#define TACH_ASPEED_IER			BIT(31)
> +#define TACH_ASPEED_INVERS_LIMIT	BIT(30)
> +#define TACH_ASPEED_LOOPBACK		BIT(29)
> +#define TACH_ASPEED_ENABLE		BIT(28)
> +#define TACH_ASPEED_DEBOUNCE_MASK	GENMASK(27, 26)
> +#define TACH_ASPEED_DEBOUNCE_BIT	26
> +#define TACH_ASPEED_IO_EDGE_MASK	GENMASK(25, 24)
> +#define TACH_ASPEED_IO_EDGE_BIT		24
> +#define TACH_ASPEED_CLK_DIV_T_MASK	GENMASK(23, 20)
> +#define TACH_ASPEED_CLK_DIV_BIT		20
> +#define TACH_ASPEED_THRESHOLD_MASK	GENMASK(19, 0)
> +/* [27:26] */
> +#define DEBOUNCE_3_CLK			0x00
> +#define DEBOUNCE_2_CLK			0x01
> +#define DEBOUNCE_1_CLK			0x02
> +#define DEBOUNCE_0_CLK			0x03
> +/* [25:24] */
> +#define F2F_EDGES			0x00
> +#define R2R_EDGES			0x01
> +#define BOTH_EDGES			0x02
> +/* [23:20] */
> +/* divisor = 4 to the nth power, n = register value */
> +#define DEFAULT_TACH_DIV		1024
> +#define DIV_TO_REG(divisor)		(ilog2(divisor) >> 1)
> +
> +/* TACH Status Register */
> +#define TACH_ASPEED_STS(ch)		(((ch) * 0x10) + 0x0C)
> +
> +/*PWM_TACH_STS */
> +#define TACH_ASPEED_ISR			BIT(31)
> +#define TACH_ASPEED_PWM_OUT		BIT(25)
> +#define TACH_ASPEED_PWM_OEN		BIT(24)
> +#define TACH_ASPEED_DEB_INPUT		BIT(23)
> +#define TACH_ASPEED_RAW_INPUT		BIT(22)
> +#define TACH_ASPEED_VALUE_UPDATE	BIT(21)
> +#define TACH_ASPEED_FULL_MEASUREMENT	BIT(20)
> +#define TACH_ASPEED_VALUE_MASK		GENMASK(19, 0)
> +/**********************************************************
> + * Software setting
> + *********************************************************/
> +#define DEFAULT_FAN_PULSE_PR		2
> +struct aspeed_tach_channel_params {
> +	int limited_inverse;
> +	u16 threshold;
> +	u8 tach_edge;
> +	u8 tach_debounce;
> +	u8 pulse_pr;
> +	u32 divisor;
> +	u32 sample_period; /* unit is us */
> +	u32 polling_period; /* unit is us */
> +};
> +
> +struct aspeed_tach_data {
> +	struct device *dev;
> +	struct regmap *regmap;
> +	struct clk *clk;
> +	struct reset_control *reset;
> +	bool tach_present[TACH_ASPEED_NR_TACHS];
> +	struct aspeed_tach_channel_params *tach_channel;
> +};
> +
> +static void aspeed_tach_ch_enable(struct aspeed_tach_data *priv, u8 tach_ch,
> +				  bool enable)
> +{
> +	if (enable)
> +		regmap_set_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> +				TACH_ASPEED_ENABLE);
> +	else
> +		regmap_clear_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> +				  TACH_ASPEED_ENABLE);
> +}
> +
> +static u64 aspeed_tach_val_to_rpm(struct aspeed_tach_data *priv, u8 fan_tach_ch,
> +				  u32 tach_val)
> +{
> +	unsigned long clk_source;
> +	u64 rpm;
> +	u32 tach_div;
> +
> +	/*
> +	 * We need the mode to determine if the tach_val is double (from
> +	 * counting both edges).
> +	 */
> +	if (priv->tach_channel[fan_tach_ch].tach_edge == BOTH_EDGES)
> +		tach_val <<= 1;
> +
> +	tach_div = tach_val * (priv->tach_channel[fan_tach_ch].divisor) *
> +		   (priv->tach_channel[fan_tach_ch].pulse_pr);
> +
> +	clk_source = clk_get_rate(priv->clk);

Unless the clock rate can change (which is unlikely, I would suggest
to read it once during probe and re-use the value instead of reading it
repeatedly.

> +	dev_dbg(priv->dev, "clk %ld, tach_val %d , tach_div %d\n", clk_source,
> +		tach_val, tach_div);
> +
> +	rpm = (u64)clk_source * 60;
> +	do_div(rpm, tach_div);
> +
> +	return rpm;
> +}
> +
> +static int aspeed_get_fan_tach_ch_rpm(struct aspeed_tach_data *priv,
> +				      u8 fan_tach_ch)
> +{
> +	u32 val;
> +	u64 rpm;
> +	int ret;
> +
> +	ret = regmap_read(priv->regmap, TACH_ASPEED_STS(fan_tach_ch), &val);
> +

Please drop this empty line.

The existence of a status register makes me wonder what is in there.
Does the controller report any errors ? If so, it might be worthwile
adding attribute(s) for it.

> +	if (ret)
> +		return ret;
> +
> +	if (!(val & TACH_ASPEED_FULL_MEASUREMENT))
> +		return 0;
> +	rpm = aspeed_tach_val_to_rpm(priv, fan_tach_ch,
> +				     val & TACH_ASPEED_VALUE_MASK);
> +
> +	return rpm;
> +}
> +
> +static int aspeed_tach_hwmon_read(struct device *dev,
> +				  enum hwmon_sensor_types type, u32 attr,
> +				  int channel, long *val)
> +{
> +	struct aspeed_tach_data *priv = dev_get_drvdata(dev);
> +	u32 reg_val;
> +	int ret;
> +
> +	switch (attr) {
> +	case hwmon_fan_input:
> +		ret = aspeed_get_fan_tach_ch_rpm(priv, channel);
> +		if (ret < 0)
> +			return ret;
> +		*val = ret;
> +		break;
> +	case hwmon_fan_div:
> +		regmap_read(priv->regmap, TACH_ASPEED_CTRL(channel), &reg_val);
> +		reg_val = FIELD_GET(TACH_ASPEED_CLK_DIV_T_MASK, reg_val);
> +		*val = BIT(reg_val << 1);
> +		break;
> +	case hwmon_fan_pulses:
> +		*val = priv->tach_channel[channel].pulse_pr;
> +		break;
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +	return 0;
> +}
> +
> +static int aspeed_tach_hwmon_write(struct device *dev,
> +				   enum hwmon_sensor_types type, u32 attr,
> +				   int channel, long val)
> +{
> +	struct aspeed_tach_data *priv = dev_get_drvdata(dev);
> +
> +	switch (attr) {
> +	case hwmon_fan_div:
> +		if (!(is_power_of_2(val) && !(ilog2(val) % 2))) {
> +			dev_err(dev,
> +				"fan_div value %ld not supported. Only support power of 4\n",
> +				val);

Please refrain from error messages here. This only clogs the log as
result of user input.

The arithmetic is confusing.
		if (!is_power_of_2(val) || (ilog2(val) % 2)))

would be much less confusing and easier to understand.

> +			return -EINVAL;
> +		}

There should be a range check. The above accepts a divisor value larger than 1024.

> +		priv->tach_channel[channel].divisor = val;
> +		regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(channel),
> +				  TACH_ASPEED_CLK_DIV_T_MASK,
> +				  DIV_TO_REG(priv->tach_channel[channel].divisor)
> +					  << TACH_ASPEED_CLK_DIV_BIT);
> +		break;
> +	case hwmon_fan_pulses:
> +		priv->tach_channel[channel].pulse_pr = val;
> +		break;
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return 0;
> +}
> +
> +static umode_t aspeed_tach_dev_is_visible(const void *drvdata,
> +					  enum hwmon_sensor_types type,
> +					  u32 attr, int channel)
> +{
> +	const struct aspeed_tach_data *priv = drvdata;
> +
> +	if (!priv->tach_present[channel])
> +		return 0;
> +	switch (attr) {
> +	case hwmon_fan_input:
> +		return 0444;
> +	case hwmon_fan_div:
> +	case hwmon_fan_pulses:
> +		return 0644;
> +	}
> +	return 0;
> +}
> +
> +static const struct hwmon_ops aspeed_tach_ops = {
> +	.is_visible = aspeed_tach_dev_is_visible,
> +	.read = aspeed_tach_hwmon_read,
> +	.write = aspeed_tach_hwmon_write,
> +};
> +
> +static const struct hwmon_channel_info *aspeed_tach_info[] = {
> +	HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES,
> +			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_PULSES),
> +	NULL
> +};
> +
> +static const struct hwmon_chip_info aspeed_tach_chip_info = {
> +	.ops = &aspeed_tach_ops,
> +	.info = aspeed_tach_info,
> +};
> +
> +static void aspeed_create_fan_tach_channel(struct aspeed_tach_data *priv,
> +					   u32 tach_ch)
> +{
> +	priv->tach_present[tach_ch] = true;
> +	priv->tach_channel[tach_ch].limited_inverse = 0;
> +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> +			  TACH_ASPEED_INVERS_LIMIT,
> +			  priv->tach_channel[tach_ch].limited_inverse ?
> +				  TACH_ASPEED_INVERS_LIMIT :
> +				  0);
> +
What is the purpose of the above code ? limited_inverse is always 0.

> +	priv->tach_channel[tach_ch].tach_debounce = DEBOUNCE_3_CLK;
> +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> +			  TACH_ASPEED_DEBOUNCE_MASK,
> +			  priv->tach_channel[tach_ch].tach_debounce
> +				  << TACH_ASPEED_DEBOUNCE_BIT);
> +
> +	priv->tach_channel[tach_ch].tach_edge = F2F_EDGES;
> +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> +			  TACH_ASPEED_IO_EDGE_MASK,
> +			  priv->tach_channel[tach_ch].tach_edge
> +				  << TACH_ASPEED_IO_EDGE_BIT);
> +

limited_inverse, tach_debounce, and tach_edge are constants.
There is no need to keep constants as per-channel variables.

> +	priv->tach_channel[tach_ch].divisor = DEFAULT_TACH_DIV;
> +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> +			  TACH_ASPEED_CLK_DIV_T_MASK,
> +			  DIV_TO_REG(priv->tach_channel[tach_ch].divisor)
> +				  << TACH_ASPEED_CLK_DIV_BIT);
> +
> +	priv->tach_channel[tach_ch].threshold = 0;
> +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> +			  TACH_ASPEED_THRESHOLD_MASK,
> +			  priv->tach_channel[tach_ch].threshold);
> +

The above applies to threshold as well.

> +	priv->tach_channel[tach_ch].pulse_pr = DEFAULT_FAN_PULSE_PR;
> +
> +	aspeed_tach_ch_enable(priv, tach_ch, true);
> +}
> +

I kind of can understand that there are no devicetree properties given the
discussion around it. It is still unfortunate since being involved in that
discussion might help ensure that a generic property such as fan divisor value
ends up being supported in the upcoming generic properties.

> +static int aspeed_tach_create_fan(struct device *dev, struct device_node *child,
> +				  struct aspeed_tach_data *priv)
> +{
> +	u32 tach_channel;
> +	int ret;
> +
> +	ret = of_property_read_u32(child, "reg", &tach_channel);
> +	if (ret)
> +		return ret;
> +
> +	aspeed_create_fan_tach_channel(priv, tach_channel);
> +
> +	return 0;
> +}
> +
> +static void aspeed_tach_reset_assert(void *data)
> +{
> +	struct reset_control *rst = data;
> +
> +	reset_control_assert(rst);
> +}
> +
> +static int aspeed_tach_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *np, *child;
> +	struct aspeed_tach_data *priv;
> +	struct device *hwmon;
> +	struct platform_device *parent_dev;
> +	int ret;
> +
> +	np = dev->parent->of_node;
> +	if (!of_device_is_compatible(np, "aspeed,ast2600-pwm-tach"))
> +		return dev_err_probe(dev, -ENODEV,
> +				     "Unsupported tach device binding\n");
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +	priv->dev = &pdev->dev;
> +	priv->tach_channel =
> +		devm_kcalloc(dev, TACH_ASPEED_NR_TACHS,
> +			     sizeof(*priv->tach_channel), GFP_KERNEL);
> +	if (!priv->tach_channel)
> +		return -ENOMEM;

Why not allocate tach_channel as array within aspeed_tach_data ?

> +
> +	priv->regmap = syscon_node_to_regmap(np);
> +	if (IS_ERR(priv->regmap))
> +		return dev_err_probe(dev, PTR_ERR(priv->regmap),
> +				     "Couldn't get regmap\n");
> +	parent_dev = of_find_device_by_node(np);

Isn't that the same as dev->parent ?

> +	priv->clk = devm_clk_get_enabled(&parent_dev->dev, NULL);
> +	if (IS_ERR(priv->clk))
> +		return dev_err_probe(dev, PTR_ERR(priv->clk),
> +				     "Couldn't get clock\n");
> +
> +	priv->reset = devm_reset_control_get_shared(&parent_dev->dev, NULL);
> +	if (IS_ERR(priv->reset))
> +		return dev_err_probe(dev, PTR_ERR(priv->reset),
> +				     "Couldn't get reset control\n");
> +
> +	ret = reset_control_deassert(priv->reset);
> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "Couldn't deassert reset control\n");
> +
> +	ret = devm_add_action_or_reset(dev, aspeed_tach_reset_assert,
> +				       priv->reset);
> +	if (ret)
> +		return ret;
> +
> +	for_each_child_of_node(dev->of_node, child) {
> +		ret = aspeed_tach_create_fan(dev, child, priv);
> +		if (ret) {
> +			of_node_put(child);
> +			return ret;
> +		}
> +	}
> +
> +	hwmon = devm_hwmon_device_register_with_info(dev, "aspeed_tach", priv,
> +						     &aspeed_tach_chip_info, NULL);
> +	ret = PTR_ERR_OR_ZERO(hwmon);
> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "Failed to register hwmon device\n");
> +	return 0;

Why not return the error ? Either it is an error or it isn't. If it is
not an error, dev_err_probe() is not appropriate. If it is, the error
should be returned. Either case, if this is on purpose, it needs an
explanation.

> +}
> +
> +static const struct of_device_id of_stach_match_table[] = {
> +	{
> +		.compatible = "aspeed,ast2600-tach",
> +	},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, of_stach_match_table);
> +
> +static struct platform_driver aspeed_tach_driver = {
> +	.probe		= aspeed_tach_probe,
> +	.driver		= {
> +		.name	= "aspeed_tach",
> +		.of_match_table = of_stach_match_table,
> +	},
> +};
> +
> +module_platform_driver(aspeed_tach_driver);
> +
> +MODULE_AUTHOR("Billy Tsai <billy_tsai@aspeedtech.com>");
> +MODULE_DESCRIPTION("Aspeed ast2600 TACH device driver");
> +MODULE_LICENSE("GPL");
  

On 2022/11/23, 11:45 PM, "Guenter Roeck" <groeck7@gmail.com on behalf of linux@roeck-us.net> wrote:

    On 11/22/22 22:16, Billy Tsai wrote:
    > > +The driver provides the following sensor accesses in sysfs:
    > > +=============== ======= =====================================================
    > > +fanX_input	ro	provide current fan rotation value in RPM as reported
    > > +			by the fan to the device.
    > > +fanX_div	rw	Fan divisor: Supported value are power of 4 (1, 4, 16
    > > +                        64, ... 4194304)

    > The code doesn't support 1.

The code can support 1.


    > The existence of a status register makes me wonder what is in there.
    > Does the controller report any errors ? If so, it might be worthwile
    > adding attribute(s) for it.

    > > +	if (ret)
    > > +		return ret;
    > > +
    > > +	if (!(val & TACH_ASPEED_FULL_MEASUREMENT))
    > > +		return 0;
    > > +	rpm = aspeed_tach_val_to_rpm(priv, fan_tach_ch,
    > > +				     val & TACH_ASPEED_VALUE_MASK);
    > > +
    > > +	return rpm;

The status register is the TACH_ASPEED_FULL_MEASUREMENT which is used to indicate that
the controller doesn't detect the change in tach pin for a long time.

    > > +static void aspeed_create_fan_tach_channel(struct aspeed_tach_data *priv,
    > > +					   u32 tach_ch)
    > > +{
    > > +	priv->tach_present[tach_ch] = true;
    > > +	priv->tach_channel[tach_ch].limited_inverse = 0;
    > > +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
    > > +			  TACH_ASPEED_INVERS_LIMIT,
    > > +			  priv->tach_channel[tach_ch].limited_inverse ?
    > > +				  TACH_ASPEED_INVERS_LIMIT :
    > > +				  0);
    > > +
    > What is the purpose of the above code ? limited_inverse is always 0.

    > > +	priv->tach_channel[tach_ch].tach_debounce = DEBOUNCE_3_CLK;
    > > +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
    > > +			  TACH_ASPEED_DEBOUNCE_MASK,
    > > +			  priv->tach_channel[tach_ch].tach_debounce
    > > +				  << TACH_ASPEED_DEBOUNCE_BIT);
    > > +
    > > +	priv->tach_channel[tach_ch].tach_edge = F2F_EDGES;
    > > +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
    > > +			  TACH_ASPEED_IO_EDGE_MASK,
    > > +			  priv->tach_channel[tach_ch].tach_edge
    > > +				  << TACH_ASPEED_IO_EDGE_BIT);
    > > +

    > limited_inverse, tach_debounce, and tach_edge are constants.
    > There is no need to keep constants as per-channel variables.

    > > +	priv->tach_channel[tach_ch].divisor = DEFAULT_TACH_DIV;
    > > +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
    > > +			  TACH_ASPEED_CLK_DIV_T_MASK,
    > > +			  DIV_TO_REG(priv->tach_channel[tach_ch].divisor)
    > > +				  << TACH_ASPEED_CLK_DIV_BIT);
    > > +
    > > +	priv->tach_channel[tach_ch].threshold = 0;
    > > +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
    > > +			  TACH_ASPEED_THRESHOLD_MASK,
    > > +			  priv->tach_channel[tach_ch].threshold);
    > > +

    > The above applies to threshold as well.

The above code is used to retain the adjustable feature of the controller.
I will remove them until I add the dts property to support them.

    > > +	}
    > > +
    > > +	hwmon = devm_hwmon_device_register_with_info(dev, "aspeed_tach", priv,
    > > +						     &aspeed_tach_chip_info, NULL);
    > > +	ret = PTR_ERR_OR_ZERO(hwmon);
    > > +	if (ret)
    > > +		return dev_err_probe(dev, ret,
    > > +				     "Failed to register hwmon device\n");
    > > +	return 0;

    > Why not return the error ? Either it is an error or it isn't. If it is
    > not an error, dev_err_probe() is not appropriate. If it is, the error
    > should be returned. Either case, if this is on purpose, it needs an
    > explanation.

I have return the return value of the dev_err_probe. Did I miss someting?

Thanks

Best Regards,
Billy Tsai
  

On 11/28/22 23:08, Billy Tsai wrote:
> On 2022/11/23, 11:45 PM, "Guenter Roeck" <groeck7@gmail.com on behalf of linux@roeck-us.net> wrote:
> 
>      On 11/22/22 22:16, Billy Tsai wrote:
>      > > +The driver provides the following sensor accesses in sysfs:
>      > > +=============== ======= =====================================================
>      > > +fanX_input	ro	provide current fan rotation value in RPM as reported
>      > > +			by the fan to the device.
>      > > +fanX_div	rw	Fan divisor: Supported value are power of 4 (1, 4, 16
>      > > +                        64, ... 4194304)
> 
>      > The code doesn't support 1.
> 
> The code can support 1.
> 
Sorry, leftover from when I misread the code and thought it didn't.
> 
>      > The existence of a status register makes me wonder what is in there.
>      > Does the controller report any errors ? If so, it might be worthwile
>      > adding attribute(s) for it.
> 
>      > > +	if (ret)
>      > > +		return ret;
>      > > +
>      > > +	if (!(val & TACH_ASPEED_FULL_MEASUREMENT))
>      > > +		return 0;
>      > > +	rpm = aspeed_tach_val_to_rpm(priv, fan_tach_ch,
>      > > +				     val & TACH_ASPEED_VALUE_MASK);
>      > > +
>      > > +	return rpm;
> 
> The status register is the TACH_ASPEED_FULL_MEASUREMENT which is used to indicate that
> the controller doesn't detect the change in tach pin for a long time.
> 
>      > > +static void aspeed_create_fan_tach_channel(struct aspeed_tach_data *priv,
>      > > +					   u32 tach_ch)
>      > > +{
>      > > +	priv->tach_present[tach_ch] = true;
>      > > +	priv->tach_channel[tach_ch].limited_inverse = 0;
>      > > +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
>      > > +			  TACH_ASPEED_INVERS_LIMIT,
>      > > +			  priv->tach_channel[tach_ch].limited_inverse ?
>      > > +				  TACH_ASPEED_INVERS_LIMIT :
>      > > +				  0);
>      > > +
>      > What is the purpose of the above code ? limited_inverse is always 0.
> 
>      > > +	priv->tach_channel[tach_ch].tach_debounce = DEBOUNCE_3_CLK;
>      > > +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
>      > > +			  TACH_ASPEED_DEBOUNCE_MASK,
>      > > +			  priv->tach_channel[tach_ch].tach_debounce
>      > > +				  << TACH_ASPEED_DEBOUNCE_BIT);
>      > > +
>      > > +	priv->tach_channel[tach_ch].tach_edge = F2F_EDGES;
>      > > +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
>      > > +			  TACH_ASPEED_IO_EDGE_MASK,
>      > > +			  priv->tach_channel[tach_ch].tach_edge
>      > > +				  << TACH_ASPEED_IO_EDGE_BIT);
>      > > +
> 
>      > limited_inverse, tach_debounce, and tach_edge are constants.
>      > There is no need to keep constants as per-channel variables.
> 
>      > > +	priv->tach_channel[tach_ch].divisor = DEFAULT_TACH_DIV;
>      > > +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
>      > > +			  TACH_ASPEED_CLK_DIV_T_MASK,
>      > > +			  DIV_TO_REG(priv->tach_channel[tach_ch].divisor)
>      > > +				  << TACH_ASPEED_CLK_DIV_BIT);
>      > > +
>      > > +	priv->tach_channel[tach_ch].threshold = 0;
>      > > +	regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
>      > > +			  TACH_ASPEED_THRESHOLD_MASK,
>      > > +			  priv->tach_channel[tach_ch].threshold);
>      > > +
> 
>      > The above applies to threshold as well.
> 
> The above code is used to retain the adjustable feature of the controller.
> I will remove them until I add the dts property to support them.
> 
>      > > +	}
>      > > +
>      > > +	hwmon = devm_hwmon_device_register_with_info(dev, "aspeed_tach", priv,
>      > > +						     &aspeed_tach_chip_info, NULL);
>      > > +	ret = PTR_ERR_OR_ZERO(hwmon);
>      > > +	if (ret)
>      > > +		return dev_err_probe(dev, ret,
>      > > +				     "Failed to register hwmon device\n");
>      > > +	return 0;
> 
>      > Why not return the error ? Either it is an error or it isn't. If it is
>      > not an error, dev_err_probe() is not appropriate. If it is, the error
>      > should be returned. Either case, if this is on purpose, it needs an
>      > explanation.
> 
> I have return the return value of the dev_err_probe. Did I miss someting?
> 
No, me not having enough coffee when reviewing the code. Sorry for the noise.

Thanks,
Guenter