linux-kernel - Re: thermal/drivers/tegra: Getting rid of the get_thermal

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Date:   Thu, 26 Jan 2023 16:37:37 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Wei Ni <wni@...dia.com>, "Rafael J. Wysocki" <rafael@...nel.org>,
        Jon Hunter <jonathanh@...dia.com>,
        Johan Hovold <johan@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        Linux PM mailing list <linux-pm@...r.kernel.org>
Subject: Re: thermal/drivers/tegra: Getting rid of the get_thermal_instance()
 usage

On 26/01/2023 13:55, Thierry Reding wrote:
> On Tue, Jan 24, 2023 at 08:57:23PM +0100, Daniel Lezcano wrote:
>>
>> Hi,
>>
>> does anyone know what is the purpose of the get_thermal_instance() usage in
>> this code:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/thermal/linux.git/tree/drivers/thermal/tegra/soctherm.c?h=thermal/linux-next#n623
>>
>> The driver is using a function which is reserved for the thermal core. It
>> should not.
>>
>> Is the following change ok ?
>>
>> diff --git a/drivers/thermal/tegra/soctherm.c
>> b/drivers/thermal/tegra/soctherm.c
>> index 220873298d77..5f552402d987 100644
>> --- a/drivers/thermal/tegra/soctherm.c
>> +++ b/drivers/thermal/tegra/soctherm.c
>> @@ -620,9 +620,8 @@ static int tegra_thermctl_set_trip_temp(struct
>> thermal_zone_device *tz, int trip
>>   				continue;
>>
>>   			cdev = ts->throt_cfgs[i].cdev;
>> -			if (get_thermal_instance(tz, cdev, trip_id))
>> -				stc = find_throttle_cfg_by_name(ts, cdev->type);
>> -			else
>> +			stc = find_throttle_cfg_by_name(ts, cdev->type);
>> +			if (!stc)
>>   				continue;
>>
>>   			return throttrip_program(dev, sg, stc, temp);
>> @@ -768,9 +767,9 @@ static int tegra_soctherm_set_hwtrips(struct device
>> *dev,
>>   			continue;
>>
>>   		cdev = ts->throt_cfgs[i].cdev;
>> -		if (get_thermal_instance(tz, cdev, trip))
>> -			stc = find_throttle_cfg_by_name(ts, cdev->type);
>> -		else
>> +
>> +		stc = find_throttle_cfg_by_name(ts, cdev->type);
>> +		if (!stc)
>>   			continue;
>>
>>   		ret = throttrip_program(dev, sg, stc, temperature);
> 
> There's a small difference in behavior after applying this patch. Prior
> to this I get (on Tegra210):
> 
> 	[   12.354091] tegra_soctherm 700e2000.thermal-sensor: missing thermtrips, will use critical trips as shut down temp
> 	[   12.379009] tegra_soctherm 700e2000.thermal-sensor: thermtrip: will shut down when cpu reaches 102500 mC
> 	[   12.388882] tegra_soctherm 700e2000.thermal-sensor: programming throttle for cpu to 102500
> 	[   12.401007] tegra_soctherm 700e2000.thermal-sensor: throttrip: will throttle when cpu reaches 102500 mC
> 	[   12.471041] tegra_soctherm 700e2000.thermal-sensor: thermtrip: will shut down when gpu reaches 103000 mC
> 	[   12.482852] tegra_soctherm 700e2000.thermal-sensor: programming throttle for gpu to 103000
> 	[   12.482860] tegra_soctherm 700e2000.thermal-sensor: throttrip: will throttle when gpu reaches 103000 mC
> 	[   12.485357] tegra_soctherm 700e2000.thermal-sensor: thermtrip: will shut down when pll reaches 103000 mC
> 	[   12.501774] tegra_soctherm 700e2000.thermal-sensor: thermtrip: will shut down when mem reaches 103000 mC
> 
> and after these changes, it turns into:
> 
> 	[   12.447113] tegra_soctherm 700e2000.thermal-sensor: missing thermtrips, will use critical trips as shut down temp
> 	[   12.472300] tegra_soctherm 700e2000.thermal-sensor: thermtrip: will shut down when cpu reaches 102500 mC
> 	[   12.481789] tegra_soctherm 700e2000.thermal-sensor: programming throttle for cpu to 102500
> 	[   12.495447] tegra_soctherm 700e2000.thermal-sensor: throttrip: will throttle when cpu reaches 102500 mC
> 	[   12.496514] tegra_soctherm 700e2000.thermal-sensor: thermtrip: will shut down when gpu reaches 103000 mC
> 	[   12.510353] tegra_soctherm 700e2000.thermal-sensor: programming throttle for gpu to 103000
> 	[   12.526856] tegra_soctherm 700e2000.thermal-sensor: throttrip: will throttle when gpu reaches 103000 mC
> 	[   12.528774] tegra_soctherm 700e2000.thermal-sensor: thermtrip: will shut down when pll reaches 103000 mC
> 	[   12.569352] tegra_soctherm 700e2000.thermal-sensor: programming throttle for pll to 103000
> 	[   12.577635] tegra_soctherm 700e2000.thermal-sensor: throttrip: will throttle when pll reaches 103000 mC
> 	[   12.590952] tegra_soctherm 700e2000.thermal-sensor: thermtrip: will shut down when mem reaches 103000 mC
> 	[   12.600783] tegra_soctherm 700e2000.thermal-sensor: programming throttle for mem to 103000
> 	[   12.609204] tegra_soctherm 700e2000.thermal-sensor: throttrip: will throttle when mem reaches 103000 mC
> 
> The "programming throttle ..." messages are something I've added locally
> to trace what gets called. So it looks like for "pll" and "mem" thermal
> zones, we now program trip points whereas we previously didn't.

Hmm, yeah. I did go into the details of the driver but if there is no 
cooling device associated with a trip point it will result in a noop 
from the thermal framework POV. The check is done in the governors by 
going through the thermal zone device list and cdev.


> I'll take a closer look to see if we can replace the calls to
> get_thermal_instance() by something else.

That is great, thanks !



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