[PATCH V2 7/9] hwmon: pwm-fan: add sysfs node to read rpm of fan

[Rajkumar Rampelli <rrajk@nvidia.com>]

Add fan device attribute fan1_input in pwm-fan driver
to read speed of fan in rotations per minute.

Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
---

V2: Removed generic-pwm-tachometer driver and using pwm-fan driver as per suggestions
    to read fan speed.
    Added fan device attribute to report speed of fan in rpms through hwmon sysfs.

 drivers/hwmon/pwm-fan.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index 70cc0d1..8dda209 100644
--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -98,11 +98,34 @@ static ssize_t show_pwm(struct device *dev,
 	return sprintf(buf, "%u\n", ctx->pwm_value);
 }
 
+static ssize_t show_rpm(struct device *dev, struct device_attribute *attr,
+			char *buf)
+{
+	struct pwm_fan_ctx *ptt = dev_get_drvdata(dev);
+	struct pwm_device *pwm = ptt->pwm;
+	struct pwm_capture result;
+	unsigned int rpm = 0;
+	int ret;
+
+	ret = pwm_capture(pwm, &result, 0);
+	if (ret < 0) {
+		pr_err("Failed to capture PWM: %d\n", ret);
+		return ret;
+	}
+
+	if (result.period)
+		rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
+					    result.period);
+
+	return sprintf(buf, "%u\n", rpm);
+}
 
 static SENSOR_DEVICE_ATTR(pwm1, S_IRUGO | S_IWUSR, show_pwm, set_pwm, 0);
+static SENSOR_DEVICE_ATTR(fan1_input, 0444, show_rpm, NULL, 0);
 
 static struct attribute *pwm_fan_attrs[] = {
 	&sensor_dev_attr_pwm1.dev_attr.attr,
+	&sensor_dev_attr_fan1_input.dev_attr.attr,
 	NULL,
 };
 
-- 
2.1.4