[PATCH V3 2/5] thermal: bcm2835: add thermal driver for bcm2835 soc

[Eric Anholt]

Zhang Rui <rui.zhang at intel.com> writes:

> On 四, 2016-08-18 at 11:39 -0700, Eric Anholt wrote:
>> Eric Anholt <eric at anholt.net> writes:
>> 
>> > 
>> > kernel at martin.sperl.org writes:
>> > 
>> > > 
>> > > From: Martin Sperl <kernel at 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 at 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 at 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?

Yeah.  It seems useful to be able to get the information.  Once we land
this, I hope someone can add interrupt support so that there are actual
trip points.
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