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

[Zhang Rui <rui.zhang@intel.com>]

On 五, 2016-08-19 at 11:59 -0700, Eric Anholt wrote:
> Zhang Rui <rui.zhang@intel.com> writes:
> 
> > 
> > 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_o
> > > > > ps,
> > > > > +					  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?
> 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.

sounds reasonable to me.
Another question, why you need a separate directory for a single
file, bcm2835_thermal.c?

thanks,
rui