[PATCH AUTOSEL 5.4 36/50] hwmon: (max31790) Report correct current pwm duty cycles

[Sasha Levin]

From: Guenter Roeck <linux@xxxxxxxxxxxx>

[ Upstream commit 897f6339893b741a5d68ae8e2475df65946041c2 ]

The MAX31790 has two sets of registers for pwm duty cycles, one to request
a duty cycle and one to read the actual current duty cycle. Both do not
have to be the same.

When reporting the pwm duty cycle to the user, the actual pwm duty cycle
from pwm duty cycle registers needs to be reported. When setting it, the
pwm target duty cycle needs to be written. Since we don't know the actual
pwm duty cycle after a target pwm duty cycle has been written, set the
valid flag to false to indicate that actual pwm duty cycle should be read
from the chip instead of using cached values.

Cc: Jan Kundrát <jan.kundrat@xxxxxxxxx>
Cc: Václav Kubernát <kubernat@xxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Tested-by: Václav Kubernát <kubernat@xxxxxxxxxx>
Reviewed-by: Jan Kundrát <jan.kundrat@xxxxxxxxx>
Link: https://lore.kernel.org/r/20210526154022.3223012-3-linux@xxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 Documentation/hwmon/max31790.rst | 3 ++-
 drivers/hwmon/max31790.c         | 6 +++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/Documentation/hwmon/max31790.rst b/Documentation/hwmon/max31790.rst
index 84c62a12ef3a..9f12aac4fab5 100644
--- a/Documentation/hwmon/max31790.rst
+++ b/Documentation/hwmon/max31790.rst
@@ -39,5 +39,6 @@ fan[1-12]_input    RO  fan tachometer speed in RPM
 fan[1-12]_fault    RO  fan experienced fault
 fan[1-6]_target    RW  desired fan speed in RPM
 pwm[1-6]_enable    RW  regulator mode, 0=disabled, 1=manual mode, 2=rpm mode
-pwm[1-6]           RW  fan target duty cycle (0-255)
+pwm[1-6]           RW  read: current pwm duty cycle,
+                       write: target pwm duty cycle (0-255)
 ================== === =======================================================
diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
index 117fb79ef294..344be7829d58 100644
--- a/drivers/hwmon/max31790.c
+++ b/drivers/hwmon/max31790.c
@@ -104,7 +104,7 @@ static struct max31790_data *max31790_update_device(struct device *dev)
 				data->tach[NR_CHANNEL + i] = rv;
 			} else {
 				rv = i2c_smbus_read_word_swapped(client,
-						MAX31790_REG_PWMOUT(i));
+						MAX31790_REG_PWM_DUTY_CYCLE(i));
 				if (rv < 0)
 					goto abort;
 				data->pwm[i] = rv;
@@ -299,10 +299,10 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
 			err = -EINVAL;
 			break;
 		}
-		data->pwm[channel] = val << 8;
+		data->valid = false;
 		err = i2c_smbus_write_word_swapped(client,
 						   MAX31790_REG_PWMOUT(channel),
-						   data->pwm[channel]);
+						   val << 8);
 		break;
 	case hwmon_pwm_enable:
 		fan_config = data->fan_config[channel];
-- 
2.30.2