Re: [PATCH V2 2/2] hwmon: pwm-fan: Add optional regulator support

Guenter Roeck
2019-02-07T18:18:32Z

On Thu, Feb 07, 2019 at 05:38:00PM +0100, Stefan Wahren wrote:
> This adds optional regulator support to the pwm-fan driver. This is
> necessary for pwm fans which are powered by a switchable supply.
>
> Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> ---
> drivers/hwmon/pwm-fan.c | 39 ++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
> index 2c94482..344915c 100644
> --- a/drivers/hwmon/pwm-fan.c
> +++ b/drivers/hwmon/pwm-fan.c
> @@ -23,6 +23,7 @@
> #include <linux/of.h>
> #include <linux/platform_device.h>
> #include <linux/pwm.h>
> +#include <linux/regulator/consumer.h>
> #include <linux/sysfs.h>
> #include <linux/thermal.h>
>
> @@ -31,6 +32,7 @@
> struct pwm_fan_ctx {
> struct mutex lock;
> struct pwm_device *pwm;
> + struct regulator *reg_en;
> unsigned int pwm_value;
> unsigned int pwm_fan_state;
> unsigned int pwm_fan_max_state;
> @@ -231,6 +233,21 @@ static int pwm_fan_probe(struct platform_device *pdev)
>
> platform_set_drvdata(pdev, ctx);
>
> + ctx->reg_en = devm_regulator_get_optional(&pdev->dev, "fan");
> + if (IS_ERR(ctx->reg_en)) {
> + if (PTR_ERR(ctx->reg_en) == -ENODEV)
> + ctx->reg_en = NULL;
> + else
> + return PTR_ERR(ctx->reg_en);

if PTR_ERR(ctx->reg_en) != -ENODEV)
return PTR_ERR(ctx->reg_en);
ctx->reg_en = NULL;

would be a bit easier to read and avoid an else.

> + } else {
> + ret = regulator_enable(ctx->reg_en);
> + if (ret) {
> + dev_err(&pdev->dev,
> + "Failed to enable fan supply: %d\n", ret);
> + return ret;
> + }
> + }
> +
> ctx->pwm_value = MAX_PWM;
>
> /* Set duty cycle to maximum allowed and enable PWM output */
> @@ -241,7 +258,7 @@ static int pwm_fan_probe(struct platform_device *pdev)
> ret = pwm_apply_state(ctx->pwm, &state);
> if (ret) {
> dev_err(&pdev->dev, "Failed to configure PWM\n");
> - return ret;
> + goto err_reg_disable;
> }
>
> hwmon = devm_hwmon_device_register_with_groups(&pdev->dev, "pwmfan",
> @@ -277,6 +294,10 @@ static int pwm_fan_probe(struct platform_device *pdev)
> state.enabled = false;
> pwm_apply_state(ctx->pwm, &state);
>
> +err_reg_disable:
> + if (ctx->reg_en)
> + regulator_disable(ctx->reg_en);
> +
> return ret;
> }
>
> @@ -287,6 +308,10 @@ static int pwm_fan_remove(struct platform_device *pdev)
> thermal_cooling_device_unregister(ctx->cdev);
> if (ctx->pwm_value)
> pwm_disable(ctx->pwm);
> +
> + if (ctx->reg_en)
> + regulator_disable(ctx->reg_en);
> +
> return 0;
> }
>
> @@ -299,6 +324,12 @@ static int pwm_fan_suspend(struct device *dev)
>
> pwm_get_args(ctx->pwm, &args);
>
> + if (ctx->reg_en) {
> + ret = regulator_disable(ctx->reg_en);
> + if (ret)
> + dev_err(dev, "Failed to disable fan supply: %d\n", ret);

This is a bit weird. The error is returned to the caller, but only if
ctx->pwm_value is 0. Otherwise it is ignored. This warrants an explanation
(and some selling) if it is on purpose.

> + }
> +
> if (ctx->pwm_value) {
> ret = pwm_config(ctx->pwm, 0, args.period);
> if (ret < 0)
> @@ -317,6 +348,12 @@ static int pwm_fan_resume(struct device *dev)
> unsigned long duty;
> int ret;
>
> + if (ctx->reg_en) {
> + ret = regulator_enable(ctx->reg_en);
> + if (ret)
> + dev_err(dev, "Failed to enable fan supply: %d\n", ret);

Does it really make sense here to ignore this error ? After all,
the fan will likely not work if that error really happens. Doesn't
that count as resume failure ?

> + }
> +
> if (ctx->pwm_value == 0)
> return 0;
>
> --
> 2.7.4
>