Re: [PATCH v2 16/16] hwmon: (mr75203) add debugfs to read and write temperature coefficients

Guenter Roeck
2022-08-18T23:11:17Z

On Wed, Aug 17, 2022 at 05:43:21AM +0000, Eliav Farber wrote:
> This change adds debugfs to read and write TS coefficients - g, h, j and
> cal5.
>
> The coefficients can vary between product and product, so to calibrate
> them it can be very useful to to be able to modify them on the fly.
>
> e.g.
>
> cat /sys/kernel/debug/940f23d0000.pvt/ts_coeff_cal5
> 4096
>
> echo 83000 > sys/kernel/debug/940f23d0000.pvt/ts_coeff_g
>

What happens if you write 0 into all those attributes, or 0xffffffff ?

Guenter

> Signed-off-by: Eliav Farber <farbere@amazon.com>
> ---
> drivers/hwmon/mr75203.c | 196 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 196 insertions(+)
>
> diff --git a/drivers/hwmon/mr75203.c b/drivers/hwmon/mr75203.c
> index 2898565afaab..ce34a44237e8 100644
> --- a/drivers/hwmon/mr75203.c
> +++ b/drivers/hwmon/mr75203.c
> @@ -9,6 +9,7 @@
> */
> #include <linux/bits.h>
> #include <linux/clk.h>
> +#include <linux/debugfs.h>
> #include <linux/hwmon.h>
> #include <linux/module.h>
> #include <linux/mod_devicetable.h>
> @@ -127,6 +128,7 @@ struct pvt_device {
> struct clk *clk;
> struct reset_control *rst;
> struct voltage_device *vd;
> + struct dentry *dbgfs_dir;
> u32 t_num;
> u32 p_num;
> u32 v_num;
> @@ -139,6 +141,198 @@ struct pvt_device {
> u8 vm_ch_total;
> };
>
> +static ssize_t pvt_ts_coeff_h_read(struct file *file,
> + char __user *user_buf,
> + size_t count, loff_t *ppos)
> +{
> + struct pvt_device *pvt = file->private_data;
> + char buf[16];
> + unsigned int len;
> +
> + len = sprintf(buf, "%u\n", pvt->ts_coeff_h);
> +
> + return simple_read_from_buffer(user_buf, count, ppos, buf, len);
> +}
> +
> +static ssize_t pvt_ts_coeff_h_write(struct file *file,
> + const char __user *user_buf,
> + size_t count, loff_t *ppos)
> +{
> + struct pvt_device *pvt = file->private_data;
> + int ret;
> + u32 coeff;
> +
> + ret = kstrtou32_from_user(user_buf, count, 0, &coeff);
> + if (ret)
> + return ret;
> +
> + pvt->ts_coeff_h = coeff;
> +
> + return count;
> +}
> +
> +static const struct file_operations pvt_ts_coeff_h_fops = {
> + .read = pvt_ts_coeff_h_read,
> + .write = pvt_ts_coeff_h_write,
> + .open = simple_open,
> + .owner = THIS_MODULE,
> + .llseek = default_llseek,
> +};
> +
> +static ssize_t pvt_ts_coeff_g_read(struct file *file,
> + char __user *user_buf,
> + size_t count, loff_t *ppos)
> +{
> + struct pvt_device *pvt = file->private_data;
> + char buf[16];
> + unsigned int len;
> +
> + len = sprintf(buf, "%u\n", pvt->ts_coeff_g);
> +
> + return simple_read_from_buffer(user_buf, count, ppos, buf, len);
> +}
> +
> +static ssize_t pvt_ts_coeff_g_write(struct file *file,
> + const char __user *user_buf,
> + size_t count, loff_t *ppos)
> +{
> + struct pvt_device *pvt = file->private_data;
> + int ret;
> + u32 coeff;
> +
> + ret = kstrtou32_from_user(user_buf, count, 0, &coeff);
> + if (ret)
> + return ret;
> +
> + pvt->ts_coeff_g = coeff;
> +
> + return count;
> +}
> +
> +static const struct file_operations pvt_ts_coeff_g_fops = {
> + .read = pvt_ts_coeff_g_read,
> + .write = pvt_ts_coeff_g_write,
> + .open = simple_open,
> + .owner = THIS_MODULE,
> + .llseek = default_llseek,
> +};
> +
> +static ssize_t pvt_ts_coeff_j_read(struct file *file,
> + char __user *user_buf,
> + size_t count, loff_t *ppos)
> +{
> + struct pvt_device *pvt = file->private_data;
> + char buf[16];
> + unsigned int len;
> +
> + len = sprintf(buf, "%d\n", pvt->ts_coeff_j);
> +
> + return simple_read_from_buffer(user_buf, count, ppos, buf, len);
> +}
> +
> +static ssize_t pvt_ts_coeff_j_write(struct file *file,
> + const char __user *user_buf,
> + size_t count, loff_t *ppos)
> +{
> + struct pvt_device *pvt = file->private_data;
> + int ret;
> + s32 coeff;
> +
> + ret = kstrtos32_from_user(user_buf, count, 0, &coeff);
> + if (ret)
> + return ret;
> +
> + pvt->ts_coeff_j = coeff;
> +
> + return count;
> +}
> +
> +static const struct file_operations pvt_ts_coeff_j_fops = {
> + .read = pvt_ts_coeff_j_read,
> + .write = pvt_ts_coeff_j_write,
> + .open = simple_open,
> + .owner = THIS_MODULE,
> + .llseek = default_llseek,
> +};
> +
> +static ssize_t pvt_ts_coeff_cal5_read(struct file *file,
> + char __user *user_buf,
> + size_t count, loff_t *ppos)
> +{
> + struct pvt_device *pvt = file->private_data;
> + char buf[16];
> + unsigned int len;
> +
> + len = sprintf(buf, "%u\n", pvt->ts_coeff_cal5);
> +
> + return simple_read_from_buffer(user_buf, count, ppos, buf, len);
> +}
> +
> +static ssize_t pvt_ts_coeff_cal5_write(struct file *file,
> + const char __user *user_buf,
> + size_t count, loff_t *ppos)
> +{
> + struct pvt_device *pvt = file->private_data;
> + int ret;
> + u32 coeff;
> +
> + ret = kstrtou32_from_user(user_buf, count, 0, &coeff);
> + if (ret)
> + return ret;
> +
> + if (coeff == 0)
> + return -EINVAL;
> +
> + pvt->ts_coeff_cal5 = coeff;
> +
> + return count;
> +}
> +
> +static const struct file_operations pvt_ts_coeff_cal5_fops = {
> + .read = pvt_ts_coeff_cal5_read,
> + .write = pvt_ts_coeff_cal5_write,
> + .open = simple_open,
> + .owner = THIS_MODULE,
> + .llseek = default_llseek,
> +};
> +
> +static void devm_pvt_ts_dbgfs_remove(void *data)
> +{
> + struct pvt_device *pvt = (struct pvt_device *)data;
> +
> + debugfs_remove_recursive(pvt->dbgfs_dir);
> + pvt->dbgfs_dir = NULL;
> +}
> +
> +static int pvt_ts_dbgfs_create(struct pvt_device *pvt, struct device *dev)
> +{
> + int ret;
> +
> + pvt->dbgfs_dir = debugfs_create_dir(dev_name(dev), NULL);
> + if (!pvt->dbgfs_dir) {
> + dev_err(dev, "Failed to create dbgfs_dir\n");
> + return -EINVAL;
> + }
> +
> + debugfs_create_file("ts_coeff_h", 0644, pvt->dbgfs_dir, pvt,
> + &pvt_ts_coeff_h_fops);
> + debugfs_create_file("ts_coeff_g", 0644, pvt->dbgfs_dir, pvt,
> + &pvt_ts_coeff_g_fops);
> + debugfs_create_file("ts_coeff_j", 0644, pvt->dbgfs_dir, pvt,
> + &pvt_ts_coeff_j_fops);
> + debugfs_create_file("ts_coeff_cal5", 0644, pvt->dbgfs_dir, pvt,
> + &pvt_ts_coeff_cal5_fops);
> +
> + ret = devm_add_action_or_reset(dev, devm_pvt_ts_dbgfs_remove, pvt);
> + if (ret) {
> + dev_err(dev, "failed to add action to remove pvt dbgfs (%d)\n",
> + ret);
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> static umode_t pvt_is_visible(const void *data, enum hwmon_sensor_types type,
> u32 attr, int channel)
> {
> @@ -655,6 +849,8 @@ static int mr75203_probe(struct platform_device *pdev)
> dev_dbg(dev, "ts-coeff: h = %u, g = %u, j = %d, cal5 = %u\n",
> pvt->ts_coeff_h, pvt->ts_coeff_g, pvt->ts_coeff_j,
> pvt->ts_coeff_cal5);
> +
> + pvt_ts_dbgfs_create(pvt, dev);
> }
>
> if (pd_num) {