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SubjectRe: [v6 4/4] hwmon: Add Aspeed ast2600 TACH support
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@aspeedtech.com>
> ---
> 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@aspeedtech.com>
> +
> +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@aspeedtech.com>");
> +MODULE_DESCRIPTION("Aspeed ast2600 TACH device driver");
> +MODULE_LICENSE("GPL");

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