linux-kernel - Re: [PATCH v2 3/3] thermal: cv180x: Add cv180x thermal driver support

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Message-ID:
 <IA1PR20MB4953143BAB9D9C82799F9C14BBCD2@IA1PR20MB4953.namprd20.prod.outlook.com>
Date: Mon, 17 Jun 2024 19:35:23 +0800
From: Inochi Amaoto <inochiama@...look.com>
To: Haylen Chu <heylenay@...look.com>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Zhang Rui <rui.zhang@...el.com>, Lukasz Luba <lukasz.luba@....com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Chen Wang <unicorn_wang@...look.com>, Inochi Amaoto <inochiama@...look.com>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Jisheng Zhang <jszhang@...nel.org>
Cc: linux-pm@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 3/3] thermal: cv180x: Add cv180x thermal driver support

>On Fri, Jun 07, 2024 at 06:36:53AM +0800, Inochi Amaoto wrote:
>>> + *	Raw register value to temperature (mC) formula:
>>> + *
>>> + *		       read_val * 1000 * 716
>>> + *	Temperature = ----------------------- - 273000
>>> + *				divider
>>> + *
>>> + *	where divider should be ticks number of accumulation period,
>>> + *	e.g. 2048 for TEMPSEN_CTRL_ACCSEL_2048T
>>> + */
>>> +static int cv180x_calc_temp(struct cv180x_thermal_zone *ctz, u32 result)
>>> +{
>>> +	u32 divider = (u32)(512 * int_pow(2, ctz->accum_period));
>>> +
>>> +	return (result * 1000) * 716 / divider - 273000;
>>> +}
>>> +
>>
>> According to the staff from Sophgo, the original formula is just done 
>> by curve fitting. And the formula is not affected by any parameters.
>> Those parameters only affect timing.
>
> No, accumulation period does affect the raw register value of
> temperature. With the original formula where divider is a constant
> (2048), an accumulation period configuration differing from 2048T
> results in obviously wrong temperature.
>

Yes, you are right, I have confirmed. Thanks.

>> Although this is still uncertainty about how to calculate the temp,
>> I suspect you did not test your patch well, and the formula you wrote
>> is obviously broken. Please test your patch in all conditions.
>
> With the formula and different configuration, I get results with a range
> of about 1 Celsius degree, which should be enough for monitoring SoC
> status.

Excellect. I think it is pretty good.


And there are some extra suggestion for you:

Always reply e-mail in group reply mode, or others will lost your
reply.

Regards,
Inochi