linux-kernel - Re: [PATCH] thermal/drivers/tsens: Add suspend to RAM support for tsens

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Date: Thu, 25 Jan 2024 12:08:05 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Priyansh Jain <quic_priyjain@...cinc.com>,
 Amit Kucheria <amitk@...nel.org>, Thara Gopinath <thara.gopinath@...il.com>,
 Bjorn Andersson <andersson@...nel.org>,
 "Rafael J . Wysocki" <rafael@...nel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>,
 Lukasz Luba <lukasz.luba@....com>, linux-pm@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: quic_manafm@...cinc.com
Subject: Re: [PATCH] thermal/drivers/tsens: Add suspend to RAM support for
 tsens

On 1/24/24 16:25, Priyansh Jain wrote:
> 
> 
> On 1/24/2024 6:04 PM, Konrad Dybcio wrote:
>>
>>
>> On 1/24/24 11:42, Priyansh Jain wrote:
>>>
>>>
>>> On 1/22/2024 8:02 PM, Konrad Dybcio wrote:
>>>> On 22.01.2024 11:07, Priyansh Jain wrote:
>>>>> Add suspend callback support for tsens which disables tsens interrupts
>>>>> in suspend to RAM callback.
>>>>
>>>> Would it not be preferrable to have the "critical overheat", wakeup-
>>>> capable interrupts be enabled, even if the system is suspended?
>>>>
>>>
>>>
>>> As part of suspend to RAM, tsens hardware will be turned off and it cannot generate any interrupt.Also system doesn't want to abort suspend to RAM due to tsens interrupts since system is already going into lowest
>>> power state. Hence disabling tsens interrupt during suspend to RAM callback.
>>
>> Is that a hardware limitation, or a software design choice? I'm not
>> sure I want my phone to have thermal notifications disabled when
>> it's suspended.
> 
>> Konrad
> 
> As part of suspend to RAM , entire SOC will be off,

What do you mean by "entire SOC[sic] will be off"? Surely the memory
controller must be on to keep refreshing the memory? Are you thinking
of suspend-to-disk (hibernation), by chance?

> this mode (suspend to RAM) is not intended for Mobile product. Tsens interrupts are not
> disabled as part of suspend to idle(suspend mode for mobile).

That's clearly untrue, e.g. the PSCI firmware on SM8550 implements
PSCI_SYSTEM_SUSPEND, which does S2R.

Konrad