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Date: Wed, 9 Nov 2016 03:53:23 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Clemens Gruber <clemens.gruber@...ruber.com>,
linux-hwmon@...r.kernel.org
Cc: Rob Herring <robh+dt@...nel.org>, Jean Delvare <jdelvare@...e.com>,
devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] hwmon: (mcp3021) rework for DT support
On 10/27/2016 03:33 PM, Clemens Gruber wrote:
> Support setting the reference voltage from the device tree.
> Rework of driver structure, put chip specific data in a separate
> structure and assign it depending on device id from platform data or
> DT match.
>
> Signed-off-by: Clemens Gruber <clemens.gruber@...ruber.com>
> ---
> Documentation/hwmon/mcp3021 | 6 ++
> drivers/hwmon/mcp3021.c | 145 ++++++++++++++++++++++++++++++++------------
> 2 files changed, 111 insertions(+), 40 deletions(-)
>
> diff --git a/Documentation/hwmon/mcp3021 b/Documentation/hwmon/mcp3021
> index 74a6b72..be252b7 100644
> --- a/Documentation/hwmon/mcp3021
> +++ b/Documentation/hwmon/mcp3021
> @@ -12,6 +12,7 @@ Supported chips:
> Authors:
> Mingkai Hu
> Sven Schuchmann <schuchmann@...leissheimer.de>
> + Clemens Gruber <clemens.gruber@...ruber.com>
>
> Description
> -----------
> @@ -27,3 +28,8 @@ Communication to the MCP3021/MCP3221 is performed using a 2-wire I2C
> compatible interface. Standard (100 kHz) and Fast (400 kHz) I2C modes are
> available. The default I2C device address is 0x4d (contact the Microchip
> factory for additional address options).
> +
> +The reference voltage used in the conversion can be set through platform data
> +in millivolt (for backwards compatibility) or via device tree in microvolt.
> +Please refer to Documentation/devicetree/bindings/i2c/mcp3021.txt for details
> +about the device tree bindings.
> diff --git a/drivers/hwmon/mcp3021.c b/drivers/hwmon/mcp3021.c
> index 972444a..a8cf97f 100644
> --- a/drivers/hwmon/mcp3021.c
> +++ b/drivers/hwmon/mcp3021.c
> @@ -4,6 +4,7 @@
> * Copyright (C) 2008-2009, 2012 Freescale Semiconductor, Inc.
> * Author: Mingkai Hu <Mingkai.hu@...escale.com>
> * Reworked by Sven Schuchmann <schuchmann@...leissheimer.de>
> + * Copyright (C) 2016 Clemens Gruber <clemens.gruber@...ruber.com>
> *
> * This driver export the value of analog input voltage to sysfs, the
> * voltage unit is mV. Through the sysfs interface, lm-sensors tool
> @@ -22,37 +23,56 @@
> #include <linux/i2c.h>
> #include <linux/err.h>
> #include <linux/device.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
>
> -/* Vdd info */
> +/* Vdd / reference voltage in millivolt */
> #define MCP3021_VDD_MAX 5500
> #define MCP3021_VDD_MIN 2700
> -#define MCP3021_VDD_REF 3300
> -
> -/* output format */
> -#define MCP3021_SAR_SHIFT 2
> -#define MCP3021_SAR_MASK 0x3ff
> -#define MCP3021_OUTPUT_RES 10 /* 10-bit resolution */
> -
> -#define MCP3221_SAR_SHIFT 0
> -#define MCP3221_SAR_MASK 0xfff
> -#define MCP3221_OUTPUT_RES 12 /* 12-bit resolution */
> +#define MCP3021_VDD_DEFAULT 3300
>
There is no technical reason to drop / change those defines and use literals
in the code instead. Please don't.
> enum chips {
> mcp3021,
> mcp3221
> };
>
> +struct mcp3021_chip_info {
> + u16 sar_shift;
> + u16 sar_mask;
> + u8 output_res;
> +};
> +
> /*
> * Client data (each client gets its own)
> */
> struct mcp3021_data {
> struct device *hwmon_dev;
> - u32 vdd; /* device power supply */
> - u16 sar_shift;
> - u16 sar_mask;
> - u8 output_res;
> + const struct mcp3021_chip_info *chip_info;
> + u32 vdd; /* device power supply and reference voltage in millivolt */
> };
>
> +static const struct mcp3021_chip_info mcp3021_chip_info_tbl[] = {
> + [mcp3021] = {
> + .sar_shift = 2,
> + .sar_mask = 0x3ff,
> + .output_res = 10, /* 10-bit resolution */
> + },
> + [mcp3221] = {
> + .sar_shift = 0,
> + .sar_mask = 0xfff,
> + .output_res = 12, /* 12-bit resolution */
> + },
> +};
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id of_mcp3021_match[] = {
> + { .compatible = "microchip,mcp3021", .data = (void *)mcp3021 },
> + { .compatible = "microchip,mcp3221", .data = (void *)mcp3221 },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, of_mcp3021_match);
> +#endif
> +
> static int mcp3021_read16(struct i2c_client *client)
> {
> struct mcp3021_data *data = i2c_get_clientdata(client);
> @@ -73,14 +93,15 @@ static int mcp3021_read16(struct i2c_client *client)
> * The ten-bit output code is composed of the lower 4-bit of the
> * first byte and the upper 6-bit of the second byte.
> */
> - reg = (reg >> data->sar_shift) & data->sar_mask;
> + reg = (reg >> data->chip_info->sar_shift) & data->chip_info->sar_mask;
>
> return reg;
> }
>
> static inline u16 volts_from_reg(struct mcp3021_data *data, u16 val)
> {
> - return DIV_ROUND_CLOSEST(data->vdd * val, 1 << data->output_res);
> + return DIV_ROUND_CLOSEST(data->vdd * val,
> + 1 << data->chip_info->output_res);
> }
>
> static ssize_t show_in_input(struct device *dev, struct device_attribute *attr,
> @@ -101,44 +122,85 @@ static ssize_t show_in_input(struct device *dev, struct device_attribute *attr,
>
> static DEVICE_ATTR(in0_input, S_IRUGO, show_in_input, NULL);
>
> -static int mcp3021_probe(struct i2c_client *client,
> +#ifdef CONFIG_OF
> +static int mcp3021_probe_dt(struct i2c_client *client,
> const struct i2c_device_id *id)
> {
> - int err;
> - struct mcp3021_data *data = NULL;
> + struct mcp3021_data *data = i2c_get_clientdata(client);
> + struct device_node *np = client->dev.of_node;
> + const struct of_device_id *match;
> + int devid, ret;
>
> - if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
> + match = of_match_device(of_mcp3021_match, &client->dev);
> + if (!match)
> return -ENODEV;
>
> - data = devm_kzalloc(&client->dev, sizeof(struct mcp3021_data),
> - GFP_KERNEL);
> - if (!data)
> - return -ENOMEM;
> -
> - i2c_set_clientdata(client, data);
> + devid = (int)(uintptr_t)match->data;
> + data->chip_info = &mcp3021_chip_info_tbl[devid];
>
> - switch (id->driver_data) {
> - case mcp3021:
> - data->sar_shift = MCP3021_SAR_SHIFT;
> - data->sar_mask = MCP3021_SAR_MASK;
> - data->output_res = MCP3021_OUTPUT_RES;
> - break;
> -
> - case mcp3221:
> - data->sar_shift = MCP3221_SAR_SHIFT;
> - data->sar_mask = MCP3221_SAR_MASK;
> - data->output_res = MCP3221_OUTPUT_RES;
> - break;
> + ret = of_property_read_u32(np, "reference-voltage-microvolt",
> + &data->vdd);
> + if (ret) {
> + /* fallback */
> + data->vdd = MCP3021_VDD_DEFAULT;
> + return 0;
> }
>
> + /* Convert microvolt from DT to millivolt used in the formula */
> + data->vdd /= 1000;
> +
> + if (data->vdd > MCP3021_VDD_MAX || data->vdd < MCP3021_VDD_MIN)
> + return -EINVAL;
> +
> + return 0;
> +}
> +#else
> +static int mcp3021_probe_dt(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + return 1;
> +}
> +#endif
> +
> +static int mcp3021_probe_pdata(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + struct mcp3021_data *data = i2c_get_clientdata(client);
> +
> + data->chip_info = &mcp3021_chip_info_tbl[id->driver_data];
> +
> if (dev_get_platdata(&client->dev)) {
> data->vdd = *(u32 *)dev_get_platdata(&client->dev);
> if (data->vdd > MCP3021_VDD_MAX || data->vdd < MCP3021_VDD_MIN)
> return -EINVAL;
> } else {
> - data->vdd = MCP3021_VDD_REF;
> + data->vdd = MCP3021_VDD_DEFAULT;
> }
>
> + return 0;
> +}
> +
> +static int mcp3021_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + struct mcp3021_data *data = NULL;
> + int err;
> +
> + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
> + return -ENODEV;
> +
> + data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + i2c_set_clientdata(client, data);
> +
> + err = mcp3021_probe_dt(client, id);
> + if (err > 0)
> + mcp3021_probe_pdata(client, id);
> + else if (err < 0)
> + return err;
> +
Most other drivers generate the platform data from devicetree data.
if (of_match_device())
pdata = probe_dt();
else
pdata = dev_get_platdata();
In this case, this is even simpler, since the only devicetree property is the reference
voltage.
if (np) {
if (of_property_read_u32(np, "reference-voltage-microvolt", &vdd))
vdd = MCP3021_VDD_REF * 1000;
vdd /= 1000;
devid = (int)(uintptr_t)match->data;
} else {
u32 *pdata = dev_get_platdata(&client->dev);
if (pdata)
vdd = *pdata;
else
vdd = MCP3021_VDD_REF;
devid = id->driver_data;
}
You should actually be able to use id->driver_data directly in both cases since it is
always passed as parameter from the i2c core.
This would be much simpler than your suggested changes.
> err = sysfs_create_file(&client->dev.kobj, &dev_attr_in0_input.attr);
> if (err)
> return err;
> @@ -176,6 +238,9 @@ MODULE_DEVICE_TABLE(i2c, mcp3021_id);
> static struct i2c_driver mcp3021_driver = {
> .driver = {
> .name = "mcp3021",
> +#ifdef CONFIG_OF
> + .of_match_table = of_match_ptr(of_mcp3021_match),
> +#endif
of_match_ptr() is already protected with #ifdef CONFIG_OF and otherwise
returns NULL, so this ifdef is unnecessary.
> },
> .probe = mcp3021_probe,
> .remove = mcp3021_remove,
>
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