Re: [v6 4/4] hwmon: Add Aspeed ast2600 TACH support

[Guenter Roeck]

On 6/7/23 19:18, Billy Tsai wrote:
> Add the support of Tachometer which can use to monitor the frequency of
> the input. In Aspeed AST2600 SoC features 16 TACH controllers, with each
> controller capable of supporting up to 1 input.

You mean there will be 16 instances of this driver ? That is weird,
confusing, and warrants a detailed explanation.

> Signed-off-by: Billy Tsai <billy_tsai@xxxxxxxxxxxxxx>
> ---
>   Documentation/hwmon/index.rst               |   1 +
>   Documentation/hwmon/tach-aspeed-ast2600.rst |  25 ++
>   drivers/hwmon/Kconfig                       |  10 +
>   drivers/hwmon/Makefile                      |   1 +
>   drivers/hwmon/tach-aspeed-ast2600.c         | 305 ++++++++++++++++++++
>   5 files changed, 342 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 ddff3c5713d7..4c3dd74675ef 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -194,6 +194,7 @@ 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..b08c73a4237f
> --- /dev/null
> +++ b/Documentation/hwmon/tach-aspeed-ast2600.rst
> @@ -0,0 +1,25 @@
> +Kernel driver tach-aspeed-ast2600
> +=================================
> +
> +Supported chips:
> +	ASPEED AST2600
> +
> +Authors:
> +	<billy_tsai@xxxxxxxxxxxxxx>
> +
> +Description:
> +------------
> +This driver implements support for ASPEED AST2600 Fan Tacho controller.
> +The controller supports up to 1 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.

Presumably, as implemented, that would be 16 instances, each with fan1_{input,div}.

> +=============== ======= ======================================================
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index a5253abb7ea7..5948a63e44e7 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -411,6 +411,16 @@ 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"
> +	depends on ARCH_ASPEED || COMPILE_TEST
> +	depends on HAVE_CLK && HAS_IOMEM
> +	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 c5cd7e3a67ff..a3bf5b438e0f 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..8be66ee25a31
> --- /dev/null
> +++ b/drivers/hwmon/tach-aspeed-ast2600.c
> @@ -0,0 +1,305 @@
> +// 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/module.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset.h>
> +#include <linux/sysfs.h>
> +
> +/* TACH Control Register */
> +#define TACH_ASPEED_CTRL		(0x00)
> +#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			(0x04)

Unnecesarry ()

> +
> +/*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 {
> +	u8 pulse_pr;
> +	u32 divisor;
> +};
> +
> +struct aspeed_tach_data {
> +	struct device *dev;
> +	void __iomem *base;
> +	struct clk *clk;
> +	struct reset_control *reset;
> +	bool tach_present;
> +	struct aspeed_tach_channel_params tach_channel;

Assuming that all channels have the same divisor, this structure
is really unnecessary (especially since pulse_pr should be dropped -
see below).

> +	unsigned long clk_source;
> +};
> +
> +static void aspeed_tach_ch_enable(struct aspeed_tach_data *priv, bool enable)
> +{
> +	if (enable)
> +		writel(readl(priv->base + TACH_ASPEED_CTRL) |
> +			       (TACH_ASPEED_ENABLE),
> +		       priv->base + TACH_ASPEED_CTRL);
> +	else
> +		writel(readl(priv->base + TACH_ASPEED_CTRL) &
> +			       ~(TACH_ASPEED_ENABLE),

Unnecessary () around TACH_ASPEED_ENABLE.

> +		       priv->base + TACH_ASPEED_CTRL);
> +}
> +
> +static u64 aspeed_tach_val_to_rpm(struct aspeed_tach_data *priv, u32 tach_val)
> +{
> +	u64 rpm;
> +	u32 tach_div;
> +
> +	tach_div = tach_val * (priv->tach_channel.divisor) *
> +		   (priv->tach.channel.pulse_pr);
> +

Unnecessary () around priv->tach_channel.pulse_pr and priv->tach_channel.divisor.
I am not going to look further for those. Please make sure you drop them all.

> +	dev_dbg(priv->dev, "clk %ld, tach_val %d , tach_div %d\n",
> +		priv->clk_source, tach_val, tach_div);
> +
> +	rpm = (u64)priv->clk_source * 60;
> +	do_div(rpm, tach_div);
> +
> +	return rpm;

This function should really return an integer.

> +}
> +
> +static int aspeed_get_fan_tach_ch_rpm(struct aspeed_tach_data *priv)
> +{
> +	u32 val;
> +	u64 rpm;
> +
> +	val = readl(priv->base + TACH_ASPEED_STS);
> +
> +	if (!(val & TACH_ASPEED_FULL_MEASUREMENT))
> +		return 0;
> +	rpm = aspeed_tach_val_to_rpm(priv, val & TACH_ASPEED_VALUE_MASK);
> +
> +	return rpm;

The 'rpm' variable is unnecessary.

> +}
> +
> +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);
> +		if (ret < 0)
> +			return ret;

Why ? The called code never returns a negative value.

> +		*val = ret;
> +		break;
> +	case hwmon_fan_div:
> +		reg_val = readl(priv->base + TACH_ASPEED_CTRL);
> +		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.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))
> +			return -EINVAL;
> +		else if (DIV_TO_REG(val) > 0xb)

Else after return is unnecessary

> +			return -ERANGE;

Math result not representable ? Not really.

> +		priv->tach_channel.divisor = val;
> +		writel((readl(priv->base + TACH_ASPEED_CTRL) &
> +			~(TACH_ASPEED_CLK_DIV_T_MASK)) |

Unnecessary () around TACH_ASPEED_CLK_DIV_T_MASK.

> +			       (DIV_TO_REG(priv->tach_channel.divisor)
> +				<< TACH_ASPEED_CLK_DIV_BIT),
> +		       priv->base + TACH_ASPEED_CTRL);
> +		break;
> +	case hwmon_fan_pulses:
> +		priv->tach_channel.pulse_pr = val;


The ABI says for the pulses atribute:

                Should only be created if the chip has a register to configure
                the number of pulses. In the absence of such a register (and
                thus attribute) the value assumed by all devices is 2 pulses
                per fan revolution.

I see no evidence that there is a chip register for the number of pulses.
Please drop this attribute.

> +		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)
> +		return 0;

What is the point of instantiating the driver in this case ?

> +	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),
> +	NULL
> +};
> +
> +static const struct hwmon_chip_info aspeed_tach_chip_info = {
> +	.ops = &aspeed_tach_ops,
> +	.info = aspeed_tach_info,
> +};
> +
> +static void aspeed_present_fan_tach(struct aspeed_tach_data *priv)
> +{
> +	priv->tach_present = true;
> +	priv->tach_channel.divisor = DEFAULT_TACH_DIV;
> +	priv->tach_channel.pulse_pr = DEFAULT_FAN_PULSE_PR;
> +
> +	writel((readl(priv->base + TACH_ASPEED_CTRL) &
> +		~(TACH_ASPEED_INVERS_LIMIT | TACH_ASPEED_DEBOUNCE_MASK |
> +		  TACH_ASPEED_IO_EDGE_MASK | TACH_ASPEED_CLK_DIV_T_MASK |
> +		  TACH_ASPEED_THRESHOLD_MASK)) |
> +		       ((DEBOUNCE_3_CLK << TACH_ASPEED_DEBOUNCE_BIT) |
> +			F2F_EDGES |
> +			(DIV_TO_REG(priv->tach_channel.divisor)
> +			 << TACH_ASPEED_CLK_DIV_BIT)),
> +	       priv->base + TACH_ASPEED_CTRL);
> +
> +	aspeed_tach_ch_enable(priv, true);
> +}
> +
> +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 aspeed_tach_data *priv;
> +	struct device *hwmon;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +	priv->dev = &pdev->dev;
> +	priv->base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(priv->base))
> +		return PTR_ERR(priv->base);
> +	priv->clk = devm_clk_get_enabled(dev, NULL);
> +	if (IS_ERR(priv->clk))
> +		return dev_err_probe(dev, PTR_ERR(priv->clk),
> +				     "Couldn't get clock\n");
> +
> +	priv->clk_source = clk_get_rate(priv->clk);
> +	priv->reset = devm_reset_control_get_shared(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;
> +
> +	aspeed_present_fan_tach(priv);
> +
> +	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;
> +}
> +
> +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@xxxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("Aspeed ast2600 TACH device driver");
> +MODULE_LICENSE("GPL");