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Date:   Fri, 2 Jun 2023 15:11:37 +0200
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Subject: Re: [PATCH 2/3] thermal: qoriq_thermal: only enable supported sensors
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To:     Peng Fan <peng.fan@nxp.com>,
        "Peng Fan (OSS)" <peng.fan@oss.nxp.com>,
        "rafael@kernel.org" <rafael@kernel.org>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
        "s.hauer@pengutronix.de" <s.hauer@pengutronix.de>
Cc:     "amitk@kernel.org" <amitk@kernel.org>,
        "rui.zhang@intel.com" <rui.zhang@intel.com>,
        "andrew.smirnov@gmail.com" <andrew.smirnov@gmail.com>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "kernel@pengutronix.de" <kernel@pengutronix.de>,
        "festevam@gmail.com" <festevam@gmail.com>,
        dl-linux-imx <linux-imx@nxp.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        Alice Guo <alice.guo@nxp.com>
References: <20230516083746.63436-1-peng.fan@oss.nxp.com>
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 <DU0PR04MB9417D574603B54AEF76480AE88499@DU0PR04MB9417.eurprd04.prod.outlook.com>
From:   Daniel Lezcano <daniel.lezcano@linaro.org>
In-Reply-To: <DU0PR04MB9417D574603B54AEF76480AE88499@DU0PR04MB9417.eurprd04.prod.outlook.com>
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On 01/06/2023 11:52, Peng Fan wrote:
> Hi Daniel,
> 
>> Subject: RE: [PATCH 2/3] thermal: qoriq_thermal: only enable supported
>> sensors
>>
>>> Subject: Re: [PATCH 2/3] thermal: qoriq_thermal: only enable supported
>>> sensors
>>>
>>> On 31/05/2023 14:05, Peng Fan wrote:
>>>>> Subject: Re: [PATCH 2/3] thermal: qoriq_thermal: only enable
>>>>> supported sensors
>>>>>
>>>>> On 16/05/2023 10:37, Peng Fan (OSS) wrote:
>>>>>> From: Peng Fan <peng.fan@nxp.com>
>>>>>>
>>>>>> There are MAX 16 sensors, but not all of them supported. Such as
>>>>>> i.MX8MQ, there are only 3 sensors. Enabling all 16 sensors will
>>>>>> touch reserved bits from i.MX8MQ reference mannual, and TMU will
>>>>>> stuck, temperature will not update anymore.
>>>>>>
>>>>>> Fixes: 45038e03d633 ("thermal: qoriq: Enable all sensors before
>>>>>> registering them")
>>>>>> Signed-off-by: Peng Fan <peng.fan@nxp.com>
>>>>>> ---
>>>>>>     drivers/thermal/qoriq_thermal.c | 30 +++++++++++++++++++----------
>> -
>>>>>>     1 file changed, 19 insertions(+), 11 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/thermal/qoriq_thermal.c
>>>>>> b/drivers/thermal/qoriq_thermal.c index
>> b806a0929459..53748c4a5be1
>>>>>> 100644
>>>>>> --- a/drivers/thermal/qoriq_thermal.c
>>>>>> +++ b/drivers/thermal/qoriq_thermal.c
>>>>>> @@ -31,7 +31,6 @@
>>>>>>     #define TMR_DISABLE	0x0
>>>>>>     #define TMR_ME		0x80000000
>>>>>>     #define TMR_ALPF	0x0c000000
>>>>>> -#define TMR_MSITE_ALL	GENMASK(15, 0)
>>>>>>
>>>>>>     #define REGS_TMTMIR	0x008	/* Temperature measurement
>>>>> interval Register */
>>>>>>     #define TMTMIR_DEFAULT	0x0000000f
>>>>>> @@ -105,6 +104,11 @@ static int tmu_get_temp(struct
>>>>> thermal_zone_device *tz, int *temp)
>>>>>>     	 * within sensor range. TEMP is an 9 bit value representing
>>>>>>     	 * temperature in KelVin.
>>>>>>     	 */
>>>>>> +
>>>>>> +	regmap_read(qdata->regmap, REGS_TMR, &val);
>>>>>> +	if (!(val & TMR_ME))
>>>>>> +		return -EAGAIN;
>>>>>
>>>>> How is this change related to what is described in the changelog?
>>>>
>>>> devm_thermal_zone_of_sensor_register will invoke get temp, since we
>>>> reverted the 45038e03d633 did, we need to check TMR_ME to avoid
>>> return
>>>> invalid temperature.
>>>
>>>
>>>   From a higher perspective if the sensor won't be enabled, then the
>>> thermal zone should not be registered, the get_temp won't happen on a
>>> disabled sensor and this test won't be necessary, no ?
> 
> After thinking more, I'd prefer current logic.
> 
> We rely on devm_thermal_of_zone_register's return value to know
> whether there is a valid zone, then set sites bit, and after collected
> all site bits, we enable the thermal IP.
> 
> If move the enabling thermal IP before devm_thermal_of_zone_register,
> We need check dtb thermal zone, to know which zone is valid for current
> thermal IP. This would complicate the design.
> 
> So just checking the enabling bit in get temperature would be much
> simpler, and there just a small window before enabling thermal IP.


If the thermal zone is not described, then the thermal zone won't be 
created as it fails with -ENODEV and thus get_temp won't be called on a 
disabled site, right?

Having test in the get_temp() ops is usually the sign there is something 
wrong with the driver initialization.


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