Re: [PATCH 2/2] hwmon: Aspeed AST2400/AST2500 ADC

From: Joel Stanley
Date: Tue Feb 28 2017 - 19:58:40 EST

Next message: Joel Stanley: "Re: [PATCH 1/2] Documentation: dt-bindings: Document bindings for Aspeed AST2400/AST2500 ADC"
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In reply to: Rick Altherr: "[PATCH 2/2] hwmon: Aspeed AST2400/AST2500 ADC"
Next in thread: Joel Stanley: "Re: [PATCH 1/2] Documentation: dt-bindings: Document bindings for Aspeed AST2400/AST2500 ADC"
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On Wed, Mar 1, 2017 at 6:44 AM, Rick Altherr <raltherr@xxxxxxxxxx> wrote:
> Aspeed AST2400/AST2500 BMC SoCs include a 16 channel, 10-bit ADC. This
> driver implements reading the ADC values, enabling channels via device
> tree, and optionally providing channel labels via device tree. Low and
> high threshold interrupts are supported by the hardware but not
> implemented.
>
> Signed-off-by: Rick Altherr <raltherr@xxxxxxxxxx>

Looks good. Some minor comments below.

Is there a reason you wrote a hwmon driver instead of an iio driver? I
wasn't sure what the recommended subsystem is.

> ---
> drivers/hwmon/Kconfig | 10 ++
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/aspeed_adc.c | 383 +++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 394 insertions(+)
> create mode 100644 drivers/hwmon/aspeed_adc.c
>
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 0649d53f3d16..c99a67b4afe4 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -261,6 +261,16 @@ config SENSORS_ASC7621
> This driver can also be built as a module. If so, the module
> will be called asc7621.
>
> +config SENSORS_ASPEED_ADC
> + tristate "Aspeed AST2400/AST2500 ADC"
> + depends on ARCH_ASPEED

depends on ARCH_ASPEED || COMPILE_TEST.

> + help
> + If you say yes here you get support for the Aspeed AST2400/AST2500
> + ADC.
> +
> + This driver can also be built as a module. If so, the module
> + will be called aspeed_adc.
> +
> 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 5509edf6186a..eede049c9d0d 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -46,6 +46,7 @@ obj-$(CONFIG_SENSORS_ADT7475) += adt7475.o
> obj-$(CONFIG_SENSORS_APPLESMC) += applesmc.o
> obj-$(CONFIG_SENSORS_ARM_SCPI) += scpi-hwmon.o
> obj-$(CONFIG_SENSORS_ASC7621) += asc7621.o
> +obj-$(CONFIG_SENSORS_ASPEED_ADC) += aspeed_adc.o
> obj-$(CONFIG_SENSORS_ATXP1) += atxp1.o
> obj-$(CONFIG_SENSORS_CORETEMP) += coretemp.o
> obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
> diff --git a/drivers/hwmon/aspeed_adc.c b/drivers/hwmon/aspeed_adc.c
> new file mode 100644
> index 000000000000..098e32315264
> --- /dev/null
> +++ b/drivers/hwmon/aspeed_adc.c
> @@ -0,0 +1,383 @@
> +/*
> + * Aspeed AST2400/2500 ADC
> + *
> + * Copyright (C) 2017 Google, Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + */
> +
> +#include <asm/io.h>
> +#include <linux/clk.h>
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +
> +#define ASPEED_ADC_NUM_CHANNELS 16
> +#define ASPEED_ADC_REF_VOLTAGE 2500 /* millivolts */
> +
> +#define ASPEED_ADC_REG_ADC00 0x00
> +#define ASPEED_ADC_REG_ADC04 0x04
> +#define ASPEED_ADC_REG_ADC08 0x08
> +#define ASPEED_ADC_REG_ADC0C 0x0C
> +#define ASPEED_ADC_REG_ADC10 0x10
> +#define ASPEED_ADC_REG_ADC14 0x14
> +#define ASPEED_ADC_REG_ADC18 0x18
> +#define ASPEED_ADC_REG_ADC1C 0x1C
> +#define ASPEED_ADC_REG_ADC20 0x20
> +#define ASPEED_ADC_REG_ADC24 0x24
> +#define ASPEED_ADC_REG_ADC28 0x28
> +#define ASPEED_ADC_REG_ADC2C 0x2C

I'm not sure that these defines add any value. I'd either give them
names such as "ASPEED_ADC_ENGINE_CTRL". or just use the register
offset directly.

> +
> +#define ASPEED_ADC_OPERATION_MODE_POWER_DOWN (0x0 << 1)
> +#define ASPEED_ADC_OPERATION_MODE_STANDBY (0x1 << 1)
> +#define ASPEED_ADC_OPERATION_MODE_NORMAL (0x7 << 1)
> +
> +#define ASPEED_ADC_ENGINE_ENABLE BIT(0)
> +
> +struct aspeed_adc_data {
> + struct device *dev;
> + void __iomem *base;
> + struct clk *pclk;
> + struct mutex lock;
> + unsigned long update_interval_ms;
> + u32 enabled_channel_mask;
> + const char* channel_labels[ASPEED_ADC_NUM_CHANNELS];
> +};
> +
> +static int aspeed_adc_set_adc_clock_frequency(
> + struct aspeed_adc_data *data,
> + unsigned long desired_update_interval_ms)
> +{
> + long pclk_hz = clk_get_rate(data->pclk);
> + long adc_combined_divisor;
> + long adc_pre_divisor;
> + long adc_divisor;
> + long adc_clock_control_reg_val;
> + long num_enabled_channels = hweight32(data->enabled_channel_mask);

Some whitespace damage here.

> +
> + if (desired_update_interval_ms < 1)
> + return -EINVAL;
> +
> + /* From the AST2400 datasheet:

Nit: kernel style is to leave a blank line on the first line of
multi-line comments:

/*
* Foo
* etc

> + * adc_period_s = pclk_period_s * 2 * (pre_divisor+1) * (divisor+1)
> + *
> + * and
> + *
> + * sample_period_s = 12 * adc_period_s
> + *
> + * Substitute pclk_period_s = (1 / pclk_hz)
> + *
> + * Solve for (pre-divisor+1) * (divisor+1) as those are settings we need
> + * to program:
> + * (pre-divisor+1) * (divisor+1) = (sample_period_s * pclk_hz) / 24
> + */
> +
> + /* Assume PCLK runs at a fairly high frequency so dividing it first
> + * loses little accuracy. Also note that the above formulas have
> + * sample_period in seconds while our desired_update_interval is in
> + * milliseconds, hence the divide by 1000.
> + */
> + adc_combined_divisor = desired_update_interval_ms *
> + (pclk_hz / 24 / 1000 / num_enabled_channels);
> +
> + /* Prefer to use the ADC divisor over the ADC pre-divisor. ADC divisor
> + * is 10-bits wide so anything over 1024 must use the pre-divisor.
> + */
> + adc_pre_divisor = 1;
> + while (adc_combined_divisor/adc_pre_divisor > (1<<10)) {
> + adc_pre_divisor += 1;
> + };
> + adc_divisor = adc_combined_divisor / adc_pre_divisor;
> +
> + /* Since ADC divisor and pre-divisor are used in division, the register
> + * value is implicitly incremented by one before use. This means we
> + * need to subtract one from our calculated values above.
> + */
> + adc_pre_divisor -= 1;
> + adc_divisor -= 1;
> +
> + adc_clock_control_reg_val = (adc_pre_divisor << 17) | adc_divisor;
> +
> + mutex_lock(&data->lock);
> + data->update_interval_ms =
> + (adc_pre_divisor + 1) * (adc_divisor + 1)
> + / (pclk_hz / 24 / 1000);
> + writel(adc_clock_control_reg_val, data->base + ASPEED_ADC_REG_ADC0C);
> + mutex_unlock(&data->lock);
> +
> + return 0;
> +}
> +
> +static int aspeed_adc_get_channel_reading(struct aspeed_adc_data *data,
> + int channel, long *val)
> +{
> + u32 data_reg;
> + u32 data_reg_val;
> + long adc_val;
> +
> + /* Each 32-bit data register contains 2 10-bit ADC values. */
> + data_reg = ASPEED_ADC_REG_ADC10 + (channel / 2) * 4;
> + data_reg_val = readl(data->base + data_reg);
> + if (channel % 2 == 0) {
> + adc_val = data_reg_val & 0x3FF;
> + } else {
> + adc_val = (data_reg_val >> 16) & 0x3FF;
> + }

I wonder if you could replace the above block with:

adc_val = readw(data->base + ASPEED_ADC_REG_ADC10 + channel);

> +
> + /* Scale 10-bit input reading to millivolts. */
> + *val = adc_val * ASPEED_ADC_REF_VOLTAGE / 1024;
> +
> + return 0;
> +}
> +
> +static umode_t aspeed_adc_hwmon_is_visible(const void *_data,
> + enum hwmon_sensor_types type,
> + u32 attr, int channel)
> +{
> + const struct aspeed_adc_data* data = _data;
> +
> + if (type == hwmon_chip && attr == hwmon_chip_update_interval) {
> + return S_IRUGO | S_IWUSR;
> + } else if (type == hwmon_in) {
> + /* Only channels that are enabled should be visible. */
> + if (channel >= 0 && channel <= ASPEED_ADC_NUM_CHANNELS &&
> + (data->enabled_channel_mask & BIT(channel))) {
> +
> + /* All enabled channels have an input but labels are
> + * optional in the device tree.
> + */
> + if (attr == hwmon_in_input) {
> + return S_IRUGO;
> + } else if (attr == hwmon_in_label &&
> + data->channel_labels[channel] != NULL) {
> + return S_IRUGO;
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
> +static int aspeed_adc_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long *val)
> +{
> + struct aspeed_adc_data *data = dev_get_drvdata(dev);
> +
> + if (type == hwmon_chip && attr == hwmon_chip_update_interval) {
> + *val = data->update_interval_ms;
> + return 0;
> + } else if (type == hwmon_in && attr == hwmon_in_input) {
> + return aspeed_adc_get_channel_reading(data, channel, val);
> + }
> +
> + return -EOPNOTSUPP;
> +}
> +
> +static int aspeed_adc_hwmon_read_string(struct device *dev,
> + enum hwmon_sensor_types type,
> + u32 attr, int channel, char **str)
> +{
> + struct aspeed_adc_data *data = dev_get_drvdata(dev);
> +
> + if (type == hwmon_in && attr == hwmon_in_label) {
> + *str = (char*)data->channel_labels[channel];
> + return 0;
> + }
> +
> + return -EOPNOTSUPP;
> +}
> +
> +static int aspeed_adc_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long val)
> +{
> + struct aspeed_adc_data *data = dev_get_drvdata(dev);
> +
> + if (type == hwmon_chip && attr == hwmon_chip_update_interval) {
> + return aspeed_adc_set_adc_clock_frequency(data, val);
> + }
> +
> + return -EOPNOTSUPP;
> +}
> +
> +static const struct hwmon_ops aspeed_adc_hwmon_ops = {
> + .is_visible = aspeed_adc_hwmon_is_visible,
> + .read = aspeed_adc_hwmon_read,
> + .read_string = aspeed_adc_hwmon_read_string,
> + .write = aspeed_adc_hwmon_write,
> +};
> +
> +static const u32 aspeed_adc_hwmon_chip_config[] = {
> + HWMON_C_UPDATE_INTERVAL,
> + 0
> +};
> +
> +static const struct hwmon_channel_info aspeed_adc_hwmon_chip_channel = {
> + .type = hwmon_chip,
> + .config = aspeed_adc_hwmon_chip_config,
> +};
> +
> +static const u32 aspeed_adc_hwmon_in_config[] = {
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + HWMON_I_INPUT | HWMON_I_LABEL,
> + 0
> +};
> +
> +static const struct hwmon_channel_info aspeed_adc_hwmon_in_channel = {
> + .type = hwmon_in,
> + .config = aspeed_adc_hwmon_in_config,
> +};
> +
> +static const struct hwmon_channel_info *aspeed_adc_hwmon_channel_info[] = {
> + &aspeed_adc_hwmon_chip_channel,
> + &aspeed_adc_hwmon_in_channel,
> + NULL
> +};
> +
> +static const struct hwmon_chip_info aspeed_adc_hwmon_chip_info = {
> + .ops = &aspeed_adc_hwmon_ops,
> + .info = aspeed_adc_hwmon_channel_info,
> +};
> +
> +static int aspeed_adc_probe(struct platform_device *pdev)
> +{
> + struct aspeed_adc_data *data;
> + struct resource *res;
> + int ret;
> + struct device *hwmon_dev;
> + u32 desired_update_interval_ms;
> + u32 adc_engine_control_reg_val;
> + struct device_node* node;
> +
> + data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + data->pclk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(data->pclk)) {
> + dev_err(&pdev->dev, "clk_get failed\n");
> + return PTR_ERR(data->pclk);
> + }
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + data->base = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(data->base))
> + return PTR_ERR(data->base);
> +
> + ret = of_property_read_u32(pdev->dev.of_node,
> + "update-interval-ms", &desired_update_interval_ms);
> + if (ret < 0 || desired_update_interval_ms == 0) {
> + dev_err(&pdev->dev,
> + "Missing or zero update-interval-ms property, "
> + "defaulting to 100ms\n");

Put the string on one line so it can be easily searched for.

> + desired_update_interval_ms = 100;
> + }
> +
> + mutex_init(&data->lock);
> +
> + ret = clk_prepare_enable(data->pclk);
> + if (ret) {
> + dev_err(&pdev->dev, "failed to enable clock\n");
> + mutex_destroy(&data->lock);
> + return ret;

Strange whitespace here.

> + }
> +
> + /* Figure out which channels are marked available in the device tree. */
> + data->enabled_channel_mask = 0;
> + for_each_available_child_of_node(pdev->dev.of_node, node) {
> + u32 pval;
> + unsigned int channel;
> +
> + if (of_property_read_u32(node, "reg", &pval)) {
> + dev_err(&pdev->dev, "invalid reg on %s\n",
> + node->full_name);
> + continue;
> + }
> +
> + channel = pval;
> + if (channel >= ASPEED_ADC_NUM_CHANNELS) {
> + dev_err(&pdev->dev,
> + "invalid channel index %d on %s\n",
> + channel, node->full_name);
> + continue;
> + }
> +
> + data->enabled_channel_mask |= BIT(channel);
> +
> + /* Cache a pointer to the label if one is specified. Ignore any
> + * errors as the label property is optional.
> + */
> + of_property_read_string(node, "label", &data->channel_labels[channel]);

I was wondering how long we could keep that pointer around. I think we
are ok for the lifetime of the driver, as we hold a reference to the
node in dev.of_node.

> + }
> +
> + platform_set_drvdata(pdev, data);
> + aspeed_adc_set_adc_clock_frequency(data, desired_update_interval_ms);

This reads funny. aspeed_adc_set_clock_frequency instead?

> +
> + /* Start all the requested channels in normal mode. */
> + adc_engine_control_reg_val = (data->enabled_channel_mask << 16) |
> + ASPEED_ADC_OPERATION_MODE_NORMAL | ASPEED_ADC_ENGINE_ENABLE;
> + writel(adc_engine_control_reg_val, data->base + ASPEED_ADC_REG_ADC00);
> +
> + /* Register sysfs hooks */
> + hwmon_dev = devm_hwmon_device_register_with_info(
> + &pdev->dev, "aspeed_adc", data,
> + &aspeed_adc_hwmon_chip_info, NULL);
> + if (IS_ERR(hwmon_dev)) {
> + clk_disable_unprepare(data->pclk);
> + mutex_destroy(&data->lock);
> + return PTR_ERR(hwmon_dev);
> + }
> +
> + return 0;
> +}
> +
> +static int aspeed_adc_remove(struct platform_device *pdev) {
> + struct aspeed_adc_data *data = dev_get_drvdata(&pdev->dev);
> + clk_disable_unprepare(data->pclk);
> + mutex_destroy(&data->lock);
> + return 0;
> +}
> +
> +const struct of_device_id aspeed_adc_matches[] = {
> + { .compatible = "aspeed,ast2400-adc" },
> + { .compatible = "aspeed,ast2500-adc" },
> +};
> +MODULE_DEVICE_TABLE(of, aspeed_adc_matches);
> +
> +static struct platform_driver aspeed_adc_driver = {
> + .probe = aspeed_adc_probe,
> + .remove = aspeed_adc_remove,
> + .driver = {
> + .name = KBUILD_MODNAME,
> + .of_match_table = aspeed_adc_matches,
> + }
> +};
> +
> +module_platform_driver(aspeed_adc_driver);
> +
> +MODULE_AUTHOR("Rick Altherr <raltherr@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("Aspeed AST2400/2500 ADC Driver");
> +MODULE_LICENSE("GPL");
> --
> 2.11.0.483.g087da7b7c-goog
>

Next message: Joel Stanley: "Re: [PATCH 1/2] Documentation: dt-bindings: Document bindings for Aspeed AST2400/AST2500 ADC"
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In reply to: Rick Altherr: "[PATCH 2/2] hwmon: Aspeed AST2400/AST2500 ADC"
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