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

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Message-ID: <20150930103704.GA7858@pengutronix.de>
Date:	Wed, 30 Sep 2015 12:37:04 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Punit Agrawal <punit.agrawal@....com>
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

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.

Sascha

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