drivers/hwmon/max6639.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
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>
---
drivers/hwmon/max6639.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/hwmon/max6639.c b/drivers/hwmon/max6639.c
index 32b4d54b2076..ca8a8f58d133 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;
@@ -560,8 +561,14 @@ static int max6639_probe_child_from_dt(struct i2c_client *client,
}
err = of_property_read_u32(child, "max-rpm", &val);
- if (!err)
+ if (!err) {
data->rpm_range[i] = rpm_range_to_reg(val);
+ data->target_rpm[i] = val;
+ }
+
+ err = of_property_read_u32(child, "target-rpm", &val);
+ if (!err)
+ data->target_rpm[i] = val;
return 0;
}
@@ -573,6 +580,7 @@ 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);
@@ -639,8 +647,9 @@ 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 */
+ 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
--
2.42.0On 3/24/25 11:57, Your Name wrote:
> 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.
>
Unless I am missing something, that is not really correct. See below.
> This allows better control over fan speed during system initialization.
>
> Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
> ---
> drivers/hwmon/max6639.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hwmon/max6639.c b/drivers/hwmon/max6639.c
> index 32b4d54b2076..ca8a8f58d133 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;
> @@ -560,8 +561,14 @@ static int max6639_probe_child_from_dt(struct i2c_client *client,
> }
>
target_rpm[] is 0 here.
> err = of_property_read_u32(child, "max-rpm", &val);
> - if (!err)
> + if (!err) {
> data->rpm_range[i] = rpm_range_to_reg(val);
> + data->target_rpm[i] = val;
> + }
If there is no max-rpm property, or if there is no devicetree support,
target_rpm[i] is still 0.
> +
> + err = of_property_read_u32(child, "target-rpm", &val);
> + if (!err)
> + data->target_rpm[i] = val;
If there is neither max-rpm nor target-rpm, target_rpm[i] is still 0.
>
> return 0;
> }
> @@ -573,6 +580,7 @@ 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);
> @@ -639,8 +647,9 @@ 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 */
> + target_duty = 120 * data->target_rpm[i] / rpm_ranges[data->rpm_range[i]];
If there is no devicetree support, or if neither max-rpm nor target-rpm are
provided, target_duty will be 0, and the fans will stop.
Maybe my interpretation is wrong, but I think both target_rpm[] and rpm_range[]
will need to be initialized. Also, it seems to me that there will need to be an
upper bound for target_rpm[]; without it, it is possible that target_duty > 120,
which would probably not be a good idea.
Guenter
> + err = regmap_write(data->regmap, MAX6639_REG_TARGTDUTY(i), target_duty);
> if (err)
> return err;
> }
>
> base-commit: 2115cbeec8a3ccc69e3b7ecdf97b4472b0829cfc
Hi Guenter,
On Tue, 25 Mar 2025 at 05:00, Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 3/24/25 11:57, Your Name wrote:
> > 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.
> >
>
> Unless I am missing something, that is not really correct. See below.
>
> > This allows better control over fan speed during system initialization.
> >
> > Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
> > ---
> > drivers/hwmon/max6639.c | 15 ++++++++++++---
> > 1 file changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/hwmon/max6639.c b/drivers/hwmon/max6639.c
> > index 32b4d54b2076..ca8a8f58d133 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;
> > @@ -560,8 +561,14 @@ static int max6639_probe_child_from_dt(struct i2c_client *client,
> > }
> >
>
> target_rpm[] is 0 here.
>
> > err = of_property_read_u32(child, "max-rpm", &val);
> > - if (!err)
> > + if (!err) {
> > data->rpm_range[i] = rpm_range_to_reg(val);
> > + data->target_rpm[i] = val;
> > + }
>
> If there is no max-rpm property, or if there is no devicetree support,
> target_rpm[i] is still 0.
>
> > +
> > + err = of_property_read_u32(child, "target-rpm", &val);
> > + if (!err)
> > + data->target_rpm[i] = val;
>
> If there is neither max-rpm nor target-rpm, target_rpm[i] is still 0.
>
> >
> > return 0;
> > }
> > @@ -573,6 +580,7 @@ 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);
> > @@ -639,8 +647,9 @@ 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 */
> > + target_duty = 120 * data->target_rpm[i] / rpm_ranges[data->rpm_range[i]];
>
> If there is no devicetree support, or if neither max-rpm nor target-rpm are
> provided, target_duty will be 0, and the fans will stop.
>
> Maybe my interpretation is wrong, but I think both target_rpm[] and rpm_range[]
> will need to be initialized. Also, it seems to me that there will need to be an
> upper bound for target_rpm[]; without it, it is possible that target_duty > 120,
> which would probably not be a good idea.
Yes you're right. I missed it in my analysis.
Here is the logic that would address:
target_rpm = 120;
/* Set PWM based on target RPM if specified */
if (data->target_rpm[i] != 0 &&
data->target_rpm[i] <= rpm_ranges[data->rpm_range[i]]) {
target_duty = 120 * data->target_rpm[i] /
rpm_ranges[data->rpm_range[i]];
}
Please let me know your thoughts & suggestions.
Regards,
Naresh
>
> Guenter
>
> > + err = regmap_write(data->regmap, MAX6639_REG_TARGTDUTY(i), target_duty);
> > if (err)
> > return err;
> > }
> >
> > base-commit: 2115cbeec8a3ccc69e3b7ecdf97b4472b0829cfc
>
On 3/26/25 09:36, Naresh Solanki wrote:
> Hi Guenter,
>
> On Tue, 25 Mar 2025 at 05:00, Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> On 3/24/25 11:57, Your Name wrote:
>>> 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.
>>>
>>
>> Unless I am missing something, that is not really correct. See below.
>>
>>> This allows better control over fan speed during system initialization.
>>>
>>> Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
>>> ---
>>> drivers/hwmon/max6639.c | 15 ++++++++++++---
>>> 1 file changed, 12 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/hwmon/max6639.c b/drivers/hwmon/max6639.c
>>> index 32b4d54b2076..ca8a8f58d133 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;
>>> @@ -560,8 +561,14 @@ static int max6639_probe_child_from_dt(struct i2c_client *client,
>>> }
>>>
>>
>> target_rpm[] is 0 here.
>>
>>> err = of_property_read_u32(child, "max-rpm", &val);
>>> - if (!err)
>>> + if (!err) {
>>> data->rpm_range[i] = rpm_range_to_reg(val);
>>> + data->target_rpm[i] = val;
>>> + }
>>
>> If there is no max-rpm property, or if there is no devicetree support,
>> target_rpm[i] is still 0.
>>
>>> +
>>> + err = of_property_read_u32(child, "target-rpm", &val);
>>> + if (!err)
>>> + data->target_rpm[i] = val;
>>
>> If there is neither max-rpm nor target-rpm, target_rpm[i] is still 0.
>>
>>>
>>> return 0;
>>> }
>>> @@ -573,6 +580,7 @@ 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);
>>> @@ -639,8 +647,9 @@ 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 */
>>> + target_duty = 120 * data->target_rpm[i] / rpm_ranges[data->rpm_range[i]];
>>
>> If there is no devicetree support, or if neither max-rpm nor target-rpm are
>> provided, target_duty will be 0, and the fans will stop.
>>
>> Maybe my interpretation is wrong, but I think both target_rpm[] and rpm_range[]
>> will need to be initialized. Also, it seems to me that there will need to be an
>> upper bound for target_rpm[]; without it, it is possible that target_duty > 120,
>> which would probably not be a good idea.
> Yes you're right. I missed it in my analysis.
>
> Here is the logic that would address:
> target_rpm = 120;
> /* Set PWM based on target RPM if specified */
> if (data->target_rpm[i] != 0 &&
> data->target_rpm[i] <= rpm_ranges[data->rpm_range[i]]) {
>
> target_duty = 120 * data->target_rpm[i] /
> rpm_ranges[data->rpm_range[i]];
> }
>
> Please let me know your thoughts & suggestions.
>
I would prefer if target_rpm[] and rpm_range[] were pre-initialized with default
values in the probe function. That would avoid runtime checks.
Thanks,
Guenter
Hi Guenter,
On Wed, 26 Mar 2025 at 22:19, Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 3/26/25 09:36, Naresh Solanki wrote:
> > Hi Guenter,
> >
> > On Tue, 25 Mar 2025 at 05:00, Guenter Roeck <linux@roeck-us.net> wrote:
> >>
> >> On 3/24/25 11:57, Your Name wrote:
> >>> 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.
> >>>
> >>
> >> Unless I am missing something, that is not really correct. See below.
> >>
> >>> This allows better control over fan speed during system initialization.
> >>>
> >>> Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
> >>> ---
> >>> drivers/hwmon/max6639.c | 15 ++++++++++++---
> >>> 1 file changed, 12 insertions(+), 3 deletions(-)
> >>>
> >>> diff --git a/drivers/hwmon/max6639.c b/drivers/hwmon/max6639.c
> >>> index 32b4d54b2076..ca8a8f58d133 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;
> >>> @@ -560,8 +561,14 @@ static int max6639_probe_child_from_dt(struct i2c_client *client,
> >>> }
> >>>
> >>
> >> target_rpm[] is 0 here.
> >>
> >>> err = of_property_read_u32(child, "max-rpm", &val);
> >>> - if (!err)
> >>> + if (!err) {
> >>> data->rpm_range[i] = rpm_range_to_reg(val);
> >>> + data->target_rpm[i] = val;
> >>> + }
> >>
> >> If there is no max-rpm property, or if there is no devicetree support,
> >> target_rpm[i] is still 0.
> >>
> >>> +
> >>> + err = of_property_read_u32(child, "target-rpm", &val);
> >>> + if (!err)
> >>> + data->target_rpm[i] = val;
> >>
> >> If there is neither max-rpm nor target-rpm, target_rpm[i] is still 0.
> >>
> >>>
> >>> return 0;
> >>> }
> >>> @@ -573,6 +580,7 @@ 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);
> >>> @@ -639,8 +647,9 @@ 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 */
> >>> + target_duty = 120 * data->target_rpm[i] / rpm_ranges[data->rpm_range[i]];
> >>
> >> If there is no devicetree support, or if neither max-rpm nor target-rpm are
> >> provided, target_duty will be 0, and the fans will stop.
> >>
> >> Maybe my interpretation is wrong, but I think both target_rpm[] and rpm_range[]
> >> will need to be initialized. Also, it seems to me that there will need to be an
> >> upper bound for target_rpm[]; without it, it is possible that target_duty > 120,
> >> which would probably not be a good idea.
> > Yes you're right. I missed it in my analysis.
> >
> > Here is the logic that would address:
> > target_rpm = 120;
> > /* Set PWM based on target RPM if specified */
> > if (data->target_rpm[i] != 0 &&
> > data->target_rpm[i] <= rpm_ranges[data->rpm_range[i]]) {
> >
> > target_duty = 120 * data->target_rpm[i] /
> > rpm_ranges[data->rpm_range[i]];
> > }
> >
> > Please let me know your thoughts & suggestions.
> >
>
> I would prefer if target_rpm[] and rpm_range[] were pre-initialized with default
> values in the probe function. That would avoid runtime checks.
rpm_range is pre-initialized to 4000 RPM [1]
I can also init target_rpm[] to 4000 RPM as default along with above init.
But still there might be a case wherein DT doesn't provide max-rpm but
target-rpm is set to greater than 4000 RPM
Thus there will be a need to check to cover this kind of scenario.
Please let me know your thoughts & will implement that.
[1]https://kernel.googlesource.com/pub/scm/linux/kernel/git/groeck/linux-staging/+/hwmon-next/drivers/hwmon/max6639.c#586
Regards,
Naresh
>
> Thanks,
> Guenter
>
On 3/26/25 09:59, Naresh Solanki wrote:
> Hi Guenter,
>
> On Wed, 26 Mar 2025 at 22:19, Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> On 3/26/25 09:36, Naresh Solanki wrote:
>>> Hi Guenter,
>>>
>>> On Tue, 25 Mar 2025 at 05:00, Guenter Roeck <linux@roeck-us.net> wrote:
>>>>
>>>> On 3/24/25 11:57, Your Name wrote:
>>>>> 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.
>>>>>
>>>>
>>>> Unless I am missing something, that is not really correct. See below.
>>>>
>>>>> This allows better control over fan speed during system initialization.
>>>>>
>>>>> Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
>>>>> ---
>>>>> drivers/hwmon/max6639.c | 15 ++++++++++++---
>>>>> 1 file changed, 12 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/drivers/hwmon/max6639.c b/drivers/hwmon/max6639.c
>>>>> index 32b4d54b2076..ca8a8f58d133 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;
>>>>> @@ -560,8 +561,14 @@ static int max6639_probe_child_from_dt(struct i2c_client *client,
>>>>> }
>>>>>
>>>>
>>>> target_rpm[] is 0 here.
>>>>
>>>>> err = of_property_read_u32(child, "max-rpm", &val);
>>>>> - if (!err)
>>>>> + if (!err) {
>>>>> data->rpm_range[i] = rpm_range_to_reg(val);
>>>>> + data->target_rpm[i] = val;
>>>>> + }
>>>>
>>>> If there is no max-rpm property, or if there is no devicetree support,
>>>> target_rpm[i] is still 0.
>>>>
>>>>> +
>>>>> + err = of_property_read_u32(child, "target-rpm", &val);
>>>>> + if (!err)
>>>>> + data->target_rpm[i] = val;
>>>>
>>>> If there is neither max-rpm nor target-rpm, target_rpm[i] is still 0.
>>>>
>>>>>
>>>>> return 0;
>>>>> }
>>>>> @@ -573,6 +580,7 @@ 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);
>>>>> @@ -639,8 +647,9 @@ 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 */
>>>>> + target_duty = 120 * data->target_rpm[i] / rpm_ranges[data->rpm_range[i]];
>>>>
>>>> If there is no devicetree support, or if neither max-rpm nor target-rpm are
>>>> provided, target_duty will be 0, and the fans will stop.
>>>>
>>>> Maybe my interpretation is wrong, but I think both target_rpm[] and rpm_range[]
>>>> will need to be initialized. Also, it seems to me that there will need to be an
>>>> upper bound for target_rpm[]; without it, it is possible that target_duty > 120,
>>>> which would probably not be a good idea.
>>> Yes you're right. I missed it in my analysis.
>>>
>>> Here is the logic that would address:
>>> target_rpm = 120;
>>> /* Set PWM based on target RPM if specified */
>>> if (data->target_rpm[i] != 0 &&
>>> data->target_rpm[i] <= rpm_ranges[data->rpm_range[i]]) {
>>>
>>> target_duty = 120 * data->target_rpm[i] /
>>> rpm_ranges[data->rpm_range[i]];
>>> }
>>>
>>> Please let me know your thoughts & suggestions.
>>>
>>
>> I would prefer if target_rpm[] and rpm_range[] were pre-initialized with default
>> values in the probe function. That would avoid runtime checks.
> rpm_range is pre-initialized to 4000 RPM [1]
> I can also init target_rpm[] to 4000 RPM as default along with above init.
>
Yes.
> But still there might be a case wherein DT doesn't provide max-rpm but
> target-rpm is set to greater than 4000 RPM
> Thus there will be a need to check to cover this kind of scenario.
>
> Please let me know your thoughts & will implement that.
>
You'll need to validate target_rpm against max-rpm either way,
to make sure that target_rpm <= max_rpm.
Thanks,
Guenter
Hi Guenter,
On Wed, 26 Mar 2025 at 23:12, Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 3/26/25 09:59, Naresh Solanki wrote:
> > Hi Guenter,
> >
> > On Wed, 26 Mar 2025 at 22:19, Guenter Roeck <linux@roeck-us.net> wrote:
> >>
> >> On 3/26/25 09:36, Naresh Solanki wrote:
> >>> Hi Guenter,
> >>>
> >>> On Tue, 25 Mar 2025 at 05:00, Guenter Roeck <linux@roeck-us.net> wrote:
> >>>>
> >>>> On 3/24/25 11:57, Your Name wrote:
> >>>>> 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.
> >>>>>
> >>>>
> >>>> Unless I am missing something, that is not really correct. See below.
> >>>>
> >>>>> This allows better control over fan speed during system initialization.
> >>>>>
> >>>>> Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
> >>>>> ---
> >>>>> drivers/hwmon/max6639.c | 15 ++++++++++++---
> >>>>> 1 file changed, 12 insertions(+), 3 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/hwmon/max6639.c b/drivers/hwmon/max6639.c
> >>>>> index 32b4d54b2076..ca8a8f58d133 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;
> >>>>> @@ -560,8 +561,14 @@ static int max6639_probe_child_from_dt(struct i2c_client *client,
> >>>>> }
> >>>>>
> >>>>
> >>>> target_rpm[] is 0 here.
> >>>>
> >>>>> err = of_property_read_u32(child, "max-rpm", &val);
> >>>>> - if (!err)
> >>>>> + if (!err) {
> >>>>> data->rpm_range[i] = rpm_range_to_reg(val);
> >>>>> + data->target_rpm[i] = val;
> >>>>> + }
> >>>>
> >>>> If there is no max-rpm property, or if there is no devicetree support,
> >>>> target_rpm[i] is still 0.
> >>>>
> >>>>> +
> >>>>> + err = of_property_read_u32(child, "target-rpm", &val);
> >>>>> + if (!err)
> >>>>> + data->target_rpm[i] = val;
> >>>>
> >>>> If there is neither max-rpm nor target-rpm, target_rpm[i] is still 0.
> >>>>
> >>>>>
> >>>>> return 0;
> >>>>> }
> >>>>> @@ -573,6 +580,7 @@ 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);
> >>>>> @@ -639,8 +647,9 @@ 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 */
> >>>>> + target_duty = 120 * data->target_rpm[i] / rpm_ranges[data->rpm_range[i]];
> >>>>
> >>>> If there is no devicetree support, or if neither max-rpm nor target-rpm are
> >>>> provided, target_duty will be 0, and the fans will stop.
> >>>>
> >>>> Maybe my interpretation is wrong, but I think both target_rpm[] and rpm_range[]
> >>>> will need to be initialized. Also, it seems to me that there will need to be an
> >>>> upper bound for target_rpm[]; without it, it is possible that target_duty > 120,
> >>>> which would probably not be a good idea.
> >>> Yes you're right. I missed it in my analysis.
> >>>
> >>> Here is the logic that would address:
> >>> target_rpm = 120;
> >>> /* Set PWM based on target RPM if specified */
> >>> if (data->target_rpm[i] != 0 &&
> >>> data->target_rpm[i] <= rpm_ranges[data->rpm_range[i]]) {
> >>>
> >>> target_duty = 120 * data->target_rpm[i] /
> >>> rpm_ranges[data->rpm_range[i]];
> >>> }
> >>>
> >>> Please let me know your thoughts & suggestions.
> >>>
> >>
> >> I would prefer if target_rpm[] and rpm_range[] were pre-initialized with default
> >> values in the probe function. That would avoid runtime checks.
> > rpm_range is pre-initialized to 4000 RPM [1]
> > I can also init target_rpm[] to 4000 RPM as default along with above init.
> >
> Yes.
>
> > But still there might be a case wherein DT doesn't provide max-rpm but
> > target-rpm is set to greater than 4000 RPM
> > Thus there will be a need to check to cover this kind of scenario.
> >
> > Please let me know your thoughts & will implement that.
> >
>
> You'll need to validate target_rpm against max-rpm either way,
> to make sure that target_rpm <= max_rpm.
Will update in V2 accordingly.
Thanks for your inputs.
Regards,
Naresh
>
> Thanks,
> Guenter
>
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