Re: [PATCH 1/1] thermal/drivers/imx_sc_thermal: return -EAGAIN when SCFW turn off resource

[Daniel Lezcano]

On 16/08/2023 19:07, Frank Li wrote:
> On Wed, Aug 16, 2023 at 06:47:17PM +0200, Daniel Lezcano wrote:
> > On 16/08/2023 18:28, Frank Li wrote:
> > > On Wed, Aug 16, 2023 at 10:44:32AM +0200, Daniel Lezcano wrote:
> > > > Hi Frank,
> > > >
> > > > sorry for the delay
> > > >
> > > > On 14/07/2023 19:19, Frank Li wrote:
> > > > > On Thu, Jul 13, 2023 at 02:49:54PM +0200, Daniel Lezcano wrote:
> > > > > > On 12/07/2023 23:05, Frank Li wrote:
> > > > > > > Avoid endless print following message when SCFW turns off resource.
> > > > > > >      [ 1818.342337] thermal thermal_zone0: failed to read out thermal zone (-1)
> > > > > > >
> > > > > > > Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> > > > > > > ---
> > > > > > >      drivers/thermal/imx_sc_thermal.c | 4 +++-
> > > > > > >      1 file changed, 3 insertions(+), 1 deletion(-)
> > > > > > >
> > > > > > > diff --git a/drivers/thermal/imx_sc_thermal.c b/drivers/thermal/imx_sc_thermal.c
> > > > > > > index 8d6b4ef23746..0533d58f199f 100644
> > > > > > > --- a/drivers/thermal/imx_sc_thermal.c
> > > > > > > +++ b/drivers/thermal/imx_sc_thermal.c
> > > > > > > @@ -58,7 +58,9 @@ static int imx_sc_thermal_get_temp(struct thermal_zone_device *tz, int *temp)
> > > > > > >      	hdr->size = 2;
> > > > > > >      	ret = imx_scu_call_rpc(thermal_ipc_handle, &msg, true);
> > > > > > > -	if (ret)
> > > > > > > +	if (ret == -EPERM) /* NO POWER */
> > > > > > > +		return -EAGAIN;
> > > > > >
> > > > > > Isn't there a chain call somewhere when the resource is turned off, so the
> > > > > > thermal zone can be disabled?
> > > > >
> > > > > A possible place in drivers/firmware/imx/scu-pd.c. but I am not sure how to
> > > > > get thermal devices. I just found a API thermal_zone_get_zone_by_name(). I
> > > > > am not sure if it is good to depend on "name", which add coupling between
> > > > > two drivers and if there are external thermal devices(such as) has the
> > > > > same name, it will wrong turn off.
> > > >
> > > > Correct
> > > >
> > > > > If add power domain notification in thermal driver, I am not how to get
> > > > > other devices's pd in thermal driver.
> > > > >
> > > > > Any example I can refer?
> > > > >
> > > > > Or this is simple enough solution.
> > > >
> > > > The solution works for removing the error message but it does not solve the
> > > > root cause of the issue. The thermal zone keeps monitoring while the sensor
> > > > is down.
> > > >
> > > > So the question is why the sensor is shut down if it is in use?
> > >
> > > Do you know if there are any code I reference? I supposed it is quite common.
> >
> > Sorry, I don't get your comment
> >
> > What I meant is why is the sensor turned off if it is in use ?
>
> One typical example is cpu hotplug. The sensor is located CPU power domain.
> If CPU hotplug off,  CPU power domain will be turn off.
>
> It doesn't make sensor keep monitor such sensor when CPU already power off.
> It doesn't make sensor to keep CPU power on just because want to get sensor
> data.
>
> Anthor example is GPU, if there are GPU0 and GPU1. Most case just GPU0
> work.  GPU1 may turn off when less loading.
>
> Ideally, thermal can get notification from power domain driver.
> when such power domain turn off,  disable thermal zone.
>
> So far, I have not idea how to do that.

Ulf,

do you have a guidance to link the thermal zone and the power domain in 
order to get a poweron/off notification leading to enable/disable the 
thermal zone ?



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