From mboxrd@z Thu Jan  1 00:00:00 1970
From: Zhang Rui <rui.zhang@intel.com>
Subject: Re: [PATCH V3 2/5] thermal: bcm2835: add thermal driver for bcm2835
 soc
Date: Fri, 19 Aug 2016 15:28:14 +0800
Message-ID: <1471591694.2691.39.camel@intel.com>
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To: Eric Anholt <eric@anholt.net>, kernel@martin.sperl.org, Eduardo Valentin <edubezval@gmail.com>, Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>, Mark Rutland <mark.rutland@arm.com>, Stephen Warren <swarren@wwwdotorg.org>, Lee Jones <lee@kernel.org>, Russell King <linux@arm.linux.org.uk>, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org
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On 四, 2016-08-18 at 11:39 -0700, Eric Anholt wrote:
> Eric Anholt <eric@anholt.net> writes:
> 
> > 
> > kernel@martin.sperl.org writes:
> > 
> > > 
> > > From: Martin Sperl <kernel@martin.sperl.org>
> > > 
> > > Add basic thermal driver for bcm2835 SOC.
> > > 
> > > This driver currently relies on the firmware setting up the
> > > tsense HW block and does not set it up itself.
> > > 
> > > Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
> > > 
> > > ChangeLog:
> > >  V1 -> V2: added specific settings depending on compatiblity
> > > 	   added trip point based on register
> > > 	   setting up ctrl-register if HW is not enabled by firmware
> > > 	     as per recommendation of Eric (untested)
> > > 	   check that clock frequency is in range
> > > 	     (1.9 - 5MHz - as per comment in clk-bcm2835.c)
> > > ---
> > > 
> > > diff --git a/drivers/thermal/bcm/Makefile
> > > b/drivers/thermal/bcm/Makefile
> > > new file mode 100644
> > > index 0000000..13456d2
> > > --- /dev/null
> > > +++ b/drivers/thermal/bcm/Makefile
> > > @@ -0,0 +1 @@
> > > +obj-$(CONFIG_BCM2835_THERMAL)		:=
> > > bcm2835_thermal.o
> > > diff --git a/drivers/thermal/bcm/bcm2835_thermal.c
> > > b/drivers/thermal/bcm/bcm2835_thermal.c
> > > new file mode 100644
> > > index 0000000..73138cb
> > > --- /dev/null
> > > +++ b/drivers/thermal/bcm/bcm2835_thermal.c
> > > 
> > > +static const struct of_device_id
> > > bcm2835_thermal_of_match_table[];
> > > +static int bcm2835_thermal_probe(struct platform_device *pdev)
> > > +{
> > > 
> > > +	/* enable clock and check rate */
> > > +	clk_prepare_enable(data->clk);
> > > +	rate = clk_get_rate(data->clk);
> > > +	if ((rate < 1920000) || (rate > 5000000)) {
> > > +		dev_warn(&pdev->dev,
> > > +			 "Clock %pCn is running at %pCr Hz,
> > > which is outside the recommended range of 1.9 to 5.0 MHz\n",
> > > +			 data->clk, data->clk);
> > > +	}
> > > +
> > > +	/* register it */
> > > +	tz = thermal_zone_device_register("bcm2835_thermal",
> > > +					  1, 0, data,
> > > +					  &bcm2835_thermal_ops,
> > > +					  NULL, 0, 0);
> > I notice that the polling_delay is set to 0, but we're not using
> > interrupts to trigger the trip.  Is it valid to expose a trip
> > without a
> > polling_delay or interrupts?  Should passive_delay be set as well?
> > 
> > This is up to the thermal maintainers.  As far as I'm concerned,
> > it's:
> > 
> > Acked-by: Eric Anholt <eric@anholt.net>
> > 
> > One it lands I'll pull the defconfig and DT bits.
> Ping on this question to thermal maintainers.  I'd still love to see
> this driver land.

hmmm, how is this driver supposed to work?
With this patch set, I think the only benefit is that we can get the
temperature and trip point information via thermal sysfs interface, but
kernel thermal control is a no-op here, right?

thanks,
rui