Re: [PATCH 3/3] dt-bindings: hwmon: max31790: Add pwmout-pin-as-tach-input property

From: Chanh Nguyen
Date: Mon Mar 18 2024 - 05:54:19 EST




On 12/03/2024 00:34, 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?

There's a common fan binding now (or pending). You should use that and
this property won't be needed.

Rob

Thank Rob,

I checked in the Documentation/devicetree/bindings/hwmon/fan-common.yaml. I found the tach-ch property, but it seems define the tach channel used for fan.

tach-ch:
description:
The tach channel used for the fan.
$ref: /schemas/types.yaml#/definitions/uint8-array

I would like to define a new vendor property to configure the PWM-OUT pin to become a TACH-IN pin. So I introduce the "maxim,pwmout-pin-as-tach-input" property. Please help me share your comments!