[RESEND PATCH v2] hwmon: (max6639) : Allow setting target RPM

Your Name
2025-04-04T11:56:54Z

From: Naresh Solanki <naresh.solanki@9elements.com>

Currently, during startup, the fan is set to its maximum RPM by default,
which may not be suitable for all use cases.
This patch introduces support for specifying a target RPM via the Device
Tree property "target-rpm".

Changes:
- Added `target_rpm` field to `max6639_data` structure to store the
target RPM for each fan channel.
- Modified `max6639_probe_child_from_dt()` to read the `"target-rpm"`
property from the Device Tree and set `target_rpm` accordingly.
- Updated `max6639_init_client()` to use `target_rpm` to compute the
initial PWM duty cycle instead of defaulting to full speed (120/120).

Behavior:
- If `"target-rpm"` is specified, the fan speed is set accordingly.
- If `"target-rpm"` is not specified, the previous behavior (full speed
at startup) is retained.

This allows better control over fan speed during system initialization.

Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>

---
Changes in v2:
- Pre-init target_rpm[] to 4000 RPM
- Validate if target_rpm[] is within configured range.
---
drivers/hwmon/max6639.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/max6639.c b/drivers/hwmon/max6639.c
index 32b4d54b2076..a06346496e1d 100644
--- a/drivers/hwmon/max6639.c
+++ b/drivers/hwmon/max6639.c
@@ -80,6 +80,7 @@ struct max6639_data {
/* Register values initialized only once */
u8 ppr[MAX6639_NUM_CHANNELS]; /* Pulses per rotation 0..3 for 1..4 ppr */
u8 rpm_range[MAX6639_NUM_CHANNELS]; /* Index in above rpm_ranges table */
+ u32 target_rpm[MAX6639_NUM_CHANNELS];

/* Optional regulator for FAN supply */
struct regulator *reg;
@@ -563,6 +564,10 @@ static int max6639_probe_child_from_dt(struct i2c_client *client,
if (!err)
data->rpm_range[i] = rpm_range_to_reg(val);

+ err = of_property_read_u32(child, "target-rpm", &val);
+ if (!err)
+ data->target_rpm[i] = val;
+
return 0;
}

@@ -573,6 +578,7 @@ static int max6639_init_client(struct i2c_client *client,
const struct device_node *np = dev->of_node;
struct device_node *child;
int i, err;
+ u8 target_duty;

/* Reset chip to default values, see below for GCONFIG setup */
err = regmap_write(data->regmap, MAX6639_REG_GCONFIG, MAX6639_GCONFIG_POR);
@@ -586,6 +592,8 @@ static int max6639_init_client(struct i2c_client *client,
/* default: 4000 RPM */
data->rpm_range[0] = 1;
data->rpm_range[1] = 1;
+ data->target_rpm[0] = 4000;
+ data->target_rpm[1] = 4000;

for_each_child_of_node(np, child) {
if (strcmp(child->name, "fan"))
@@ -639,8 +647,12 @@ static int max6639_init_client(struct i2c_client *client,
if (err)
return err;

- /* PWM 120/120 (i.e. 100%) */
- err = regmap_write(data->regmap, MAX6639_REG_TARGTDUTY(i), 120);
+ /* Set PWM based on target RPM if specified */
+ if (data->target_rpm[i] > rpm_ranges[data->rpm_range[i]])
+ data->target_rpm[i] = rpm_ranges[data->rpm_range[i]];
+
+ target_duty = 120 * data->target_rpm[i] / rpm_ranges[data->rpm_range[i]];
+ err = regmap_write(data->regmap, MAX6639_REG_TARGTDUTY(i), target_duty);
if (err)
return err;
}

base-commit: 2115cbeec8a3ccc69e3b7ecdf97b4472b0829cfc
--
2.42.0