linux-kernel - Re: [PATCH 2/3] thermal: Add Mediatek thermal controller support

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Message-ID: <9hha8s45fon.fsf@e105922-lin.cambridge.arm.com>
Date:	Wed, 30 Sep 2015 12:07:04 +0100
From:	Punit Agrawal <punit.agrawal@....com>
To:	Sascha Hauer <s.hauer@...gutronix.de>
Cc:	linux-pm@...r.kernel.org, Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de,
	linux-mediatek@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	Matthias Brugger <matthias.bgg@...il.com>,
	devicetree@...r.kernel.org, mark.rutland@....com,
	robh+dt@...nel.org
Subject: Re: [PATCH 2/3] thermal: Add Mediatek thermal controller support

Sascha Hauer <s.hauer@...gutronix.de> writes:

> Hi Punit,
>
> On Wed, Sep 30, 2015 at 10:36:14AM +0100, Punit Agrawal wrote:
>> Hi Sascha,
>> 
>> Re-posting a comment from v7. Perhaps you missed it...
>
> Uh, sorry. In fact I didn't miss it and I thought I have answered it.
> Appearantly I haven't.
>
>> > +	struct mtk_thermal *mt = bank->mt;
>> > +	int temp, i, max;
>> > +	u32 raw;
>> > +
>> > +	temp = max = INT_MIN;
>> > +
>> > +	for (i = 0; i < bank_data[bank->id].num_sensors; i++) {
>> > +		raw = readl(mt->thermal_base + sensing_points[i].msr);
>> > +
>> > +		temp = raw_to_mcelsius(mt, raw);
>> > +
>> > +		/*
>> > +		 * The first read of a sensor often contains very high bogus
>> > +		 * temperature value. Filter these out so that the system does
>> > +		 * not immediately shut down.
>> > +		 */
>> > +		if (temp > 200000)
>> > +			temp = 0;
>> > +
>> 
>> If the bogus value is only the first time the sensor is read, instead of
>> filtering here, you could call mtk_thermal_bank_temperature at probe
>> time when you are initialising the banks and ignore the returned value.
>
> It seems that after initialization the hardware needs some time to
> settle before correct values can be read. Doing what you suggest would
> mean we have to delay the boot by several 100ms. I'd rather not do that.

Fair enough. Thanks for clarifying.

>
> Sascha
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