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

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Date:   Wed, 16 Aug 2023 18:47:17 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Frank Li <Frank.li@....com>
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,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH 1/1] thermal/drivers/imx_sc_thermal: return -EAGAIN when
 SCFW turn off resource

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 ?

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