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

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Message-ID: <80324fb7-3d2a-ecd3-f1ca-9745a366eb0a@linaro.org>
Date:   Wed, 16 Aug 2023 22:45:58 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Frank Li <Frank.li@....com>, Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>, imx@...ts.linux.dev
Subject: Re: [PATCH 1/1] thermal/drivers/imx_sc_thermal: return -EAGAIN when
 SCFW turn off resource

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@....com>
>>>>>>> ---
>>>>>>>      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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