On 12/03/2024 00:52, Guenter Roeck wrote:
On 3/11/24 10:34, Rob Herring wrote:
On Mon, Mar 11, 2024 at 06:13:47PM +0700, Chanh Nguyen wrote:
Add pwmout-pin-as-tach-input property.
Signed-off-by: Chanh Nguyen <chanh@xxxxxxxxxxxxxxxxxxxxxx>
---
Documentation/devicetree/bindings/hwmon/max31790.yaml | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/Documentation/devicetree/bindings/hwmon/max31790.yaml
b/Documentation/devicetree/bindings/hwmon/max31790.yaml
index 5a93e6bdebda..447cac17053a 100644
--- a/Documentation/devicetree/bindings/hwmon/max31790.yaml
+++ b/Documentation/devicetree/bindings/hwmon/max31790.yaml
@@ -25,6 +25,16 @@ properties:
reg:
maxItems: 1
+ pwmout-pin-as-tach-input:
+ description: |
+ An array of six integers responds to six PWM channels for
+ configuring the pwm to tach mode.
+ When set to 0, the associated PWMOUT produces a PWM waveform for
+ control of fan speed. When set to 1, PWMOUT becomes a TACH input
+ $ref: /schemas/types.yaml#/definitions/uint8-array
+ maxItems: 6
+ minItems: 6
Seems incomplete. For example, fan tachs have different number of
pulses per revolution, don't you need to know that too?
Per Documentation/ABI/testing/sysfs-class-hwmon:
What: /sys/class/hwmon/hwmonX/fanY_pulses
Description:
Number of tachometer pulses per fan revolution.
Integer value, typically between 1 and 4.
RW
This value is a characteristic of the fan connected to the
device's input, so it has to be set in accordance with
the fan
model.
Should only be created if the chip has a register to
configure
the number of pulses. In the absence of such a register
(and
thus attribute) the value assumed by all devices is 2
pulses
per fan revolution.
We only expect the property (and attribute) to exist if the controller
supports it.
Guenter
Hi Guenter and Rob,
Most general-purpose brushless DC fans produce two tachometer pulses per
revolution. My fan devices also produce two tachometer pulses per
revolution.
In max31790.c, I saw the formula that is used to calculate TACH Count
Registers, which defines the pulses per revolution as 2
#define RPM_TO_REG(rpm, sr) ((60 * (sr) * 8192) / ((rpm) * 2))
Do you think we should support the pulses-per-revolution property in
this case?
