On 6/7/24 09:47, Chanh Nguyen wrote:
On 08/05/2024 23:47, Conor Dooley wrote:
On Wed, May 08, 2024 at 10:44:34AM +0700, Chanh Nguyen wrote:
On 05/05/2024 22:40, Guenter Roeck wrote:
On 5/5/24 03:08, Chanh Nguyen wrote:
On 25/04/2024 21:05, Guenter Roeck wrote:
On 4/25/24 03:33, Chanh Nguyen wrote:
pwm outputs on MAX31790 are always tied to the matching
tachometer inputs
(pwm1 <--> tach1 etc) and can not be reconfigured, meaning tach-ch for
channel X would always be X.
I would like to open a discussion about whether we should
use the tach-ch property on the fan-common.yaml
I'm looking forward to hearing comments from everyone. For
me, both tach-ch and vendor property are good.
I am not even sure how to define tach-ch to mean "use the pwm output pin
associated with this tachometer input channel not as pwm output
but as tachometer input". That would be a boolean, not a number.
Thank Guenter,
I reviewed again the "tach-ch" property, which is used in the https://elixir.bootlin.com/linux/v6.9-rc6/source/Documentation/devicetree/bindings/hwmon/aspeed,g6-pwm-tach.yaml#L68
and https://elixir.bootlin.com/linux/v6.9-rc6/source/drivers/hwmon/aspeed-g6-pwm-tach.c#L434
That is something completely different from my purpose.
Based on its definition, tach-ch is associated with fans, and it looks
like the .yaml file groups multiple sets of fans into a single
fan node.
In the simple case that would be
tach-ch = <1>
...
tach-ch = <12>
or, if all fans are controlled by a single pwm
tach-ch = <1 2 3 4 5 6 8 9 10 11 12>
The existence of tachometer channel 7..12 implies that pwm channel
(tachometer
channel - 6) is used as tachometer channel. That should be sufficient to
program
the chip for that channel. All you'd have to do is to ensure that pwm
channel
"X" is not listed as tachometer channel "X + 6", and program pwm channel
"X - 6"
for tachometer channels 7..12 as tachometer channels.
Hi Guenter,
I applied the patch [2/3] in my patch series (https://lore.kernel.org/lkml/20240414042246.8681-3-chanh@xxxxxxxxxxxxxxxxxxxxxx/)
My device tree is configured as below, I would like to configure PWMOUT pins
5 and 6 to become the tachometer input pins.
fan-controller@20 {
compatible = "maxim,max31790";
reg = <0x20>;
maxim,pwmout-pin-as-tach-input = /bits/ 8 <0 0 0 0 1 1>;
};
Why are you still operating off a binding that looks like this? I
thought that both I and Krzysztof told you to go and take a look at how
the aspeed,g6-pwm-tach.yaml binding looped and do something similar
here. You'd end up with something like:
fan-controller@20 {
compatible = "maxim,max31790";
reg = <0x20>;
fan-0 {
pwms = <&pwm-provider ...>;
tach-ch = 6;
};
fan-1 {
pwms = <&pwm-provider ...>;
tach-ch = 7;
};
};
You can, as tach-ch or pwms do not need to be unique, set multiple
channels up as using the same tachs and/or pwms.
In the case of this particular fan controller, I think that the max31790
is actually the pwm provider so you'd modify it something like:
pwm-provider: fan-controller@20 {
compatible = "maxim,max31790";
reg = <0x20>;
#pwm-cells = <N>;
fan-0 {
pwms = <&pwm-provider ...>;
tach-ch = <6>;
};
fan-1 {
pwms = <&pwm-provider ...>;
tach-ch = <7>;
};
};
I just wrote this in my mail client's editor, so it may not be not
valid, but it is how the fan bindings expect you to represent this kind
of scenario.
My apologies for the late reply.
Thank you, Conor, for your recommendation!
I spend more time checking the aspeed,g6-pwm-tach.yaml . Finally, I'll support the child nodes by having different tach-ch values. My system is designed similar to Figure 6 (8 Tach Monitors, 4PMWs).
I'm going to push the patch series v3 soon.
This is a brief binding.
....
properties:
compatible:
const: maxim,max31790
reg:
maxItems: 1
clocks:
maxItems: 1
resets:
maxItems: 1
patternProperties:
"^fan-[0-9]+$":
$ref: fan-common.yaml#
unevaluatedProperties: false
required:
- compatible
- reg
additionalProperties: false
examples:
- |
i2c {
#address-cells = <1>;
#size-cells = <0>;
pwm_provider: fan-controller@20 {
compatible = "maxim,max31790";
reg = <0x20>;
clocks = <&sys_clk>;
resets = <&reset 0>;
fan-0 {
pwms = <&pwm_provider 1>;
tach-ch = <1 2>;
};
fan-1 {
pwms = <&pwm_provider 2>;
tach-ch = <7 8>;
};
};
};
As your example, I saw the #pwm-cells = <N> . Please let me know, what's the purpose of this property?
It is the number of fields in "pwms" after the provider reference.
In your case it would be 1 (the index). If the pwm has additional
configuration parameters such as the frequency or polarity there
would be additional entries.
Guenter
