linux-kernel - Re: [PATCH 1/2] thermal: tegra-bpmp: Handle offline zones

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Date:   Wed, 8 Feb 2023 17:35:48 +0200
From:   Mikko Perttunen <cyndis@...si.fi>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Srikar Srimath Tirumala <srikars@...dia.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        Timo Alho <talho@...dia.com>, linux-pm@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] thermal: tegra-bpmp: Handle offline zones

On 2/8/23 12:31, Thierry Reding wrote:
> On Tue, Feb 07, 2023 at 03:56:08PM +0200, Mikko Perttunen wrote:
>> From: Mikko Perttunen <mperttunen@...dia.com>
>>
>> Thermal zones located in power domains may not be accessible when
>> the domain is powergated. In this situation, reading the temperature
>> will return -BPMP_EFAULT and the temperature is considered to be
>> -256C for calculating trips.
> 
> Where's that -256C being set? I only see THERMAL_TEMP_INVALID being set
> as the default for a zone, but that's not -274C, not -256C. If that's
> the temperature that you're referring to, it might be better to state
> that we rely on the default temperature rather than any specific number.
> 
> Thierry

It is based on BPMP's internal behavior.

Mikko

> 
>>
>> For smooth operation, for offline zones, return -EAGAIN when reading
>> the temperature and allow registration of zones even if they are
>> offline during probe.
>>
>> Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
>> ---
>>   drivers/thermal/tegra/tegra-bpmp-thermal.c | 9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/thermal/tegra/tegra-bpmp-thermal.c b/drivers/thermal/tegra/tegra-bpmp-thermal.c
>> index c76e1ea62c8a..628b18818ae9 100644
>> --- a/drivers/thermal/tegra/tegra-bpmp-thermal.c
>> +++ b/drivers/thermal/tegra/tegra-bpmp-thermal.c
>> @@ -52,6 +52,8 @@ static int __tegra_bpmp_thermal_get_temp(struct tegra_bpmp_thermal_zone *zone,
>>   	err = tegra_bpmp_transfer(zone->tegra->bpmp, &msg);
>>   	if (err)
>>   		return err;
>> +	if (msg.rx.ret == -BPMP_EFAULT)
>> +		return -EAGAIN;
>>   	if (msg.rx.ret)
>>   		return -EINVAL;
>>   
>> @@ -257,7 +259,12 @@ static int tegra_bpmp_thermal_probe(struct platform_device *pdev)
>>   		zone->tegra = tegra;
>>   
>>   		err = __tegra_bpmp_thermal_get_temp(zone, &temp);
>> -		if (err < 0) {
>> +
>> +		/*
>> +		 * Sensors in powergated domains may temporarily fail to be read
>> +		 * (-EAGAIN), but will become accessible when the domain is powered on.
>> +		 */
>> +		if (err < 0 && err != -EAGAIN) {
>>   			devm_kfree(&pdev->dev, zone);
>>   			continue;
>>   		}
>> -- 
>> 2.39.0
>>