Re: [Patch v5 2/6] thermal: qcom: Add support for LMh driver

From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Thara Gopinath <thara.gopinath@linaro.org>,
	agross@kernel.org, rui.zhang@intel.com, viresh.kumar@linaro.org,
	rjw@rjwysocki.net, robh+dt@kernel.org, steev@kali.org,
	tdas@codeaurora.org, mka@chromium.org,
	linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [Patch v5 2/6] thermal: qcom: Add support for LMh driver
Date: Mon, 23 Aug 2021 17:57:02 +0200	[thread overview]
Message-ID: <a216c89d-6cd5-326d-f203-f48caaf2a096@linaro.org> (raw)
In-Reply-To: <YSO5Njg3DXo64InF@ripper>

Hi Bjorn,

On 23/08/2021 17:05, Bjorn Andersson wrote:
> On Sat 21 Aug 02:41 PDT 2021, Daniel Lezcano wrote:
> 
>>
>> Hi Thara,
>>
>> On 09/08/2021 21:16, Thara Gopinath wrote:
>>> Driver enabling various pieces of Limits Management Hardware(LMh) for cpu
>>> cluster0 and cpu cluster1 namely kick starting monitoring of temperature,
>>> current, battery current violations, enabling reliability algorithm and
>>> setting up various temperature limits.
>>>
>>> The following has been explained in the cover letter. I am including this
>>> here so that this remains in the commit message as well.
>>>
>>> LMh is a hardware infrastructure on some Qualcomm SoCs that can enforce
>>> temperature and current limits as programmed by software for certain IPs
>>> like CPU. On many newer LMh is configured by firmware/TZ and no programming
>>> is needed from the kernel side. But on certain SoCs like sdm845 the
>>> firmware does not do a complete programming of the h/w. On such soc's
>>> kernel software has to explicitly set up the temperature limits and turn on
>>> various monitoring and enforcing algorithms on the hardware.
>>>
>>> Tested-by: Steev Klimaszewski <steev@kali.org> # Lenovo Yoga C630
>>> Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
>>
>> Is it possible to have an option to disable/enable the LMh driver at
>> runtime, for instance with a module parameter ?
>>
> 
> Are you referring to being able to disable the hardware throttling, or
> the driver's changes to thermal pressure?

The former.

> I'm not aware of any way to disable the hardware. I do remember that
> there was some experiments done (with a hacked up boot chain) early on
> and iirc it was concluded that it's not a good idea.

My objective was to test the board with the thermal framework handling
the mitigation instead of the hardware.

I guess I can set the hardware temperature higher than the thermal zone
temperature.

On which sensor the lmh does refer to ? The cluster one ?

(by the way the thermal zone temperatures per core are lower by 5°C than
the hardware mitigation ? is it done on purpose ?)

> Either way, if there is a way and there is a use for it, we can always
> add such parameter incrementally. So I suggest that we merge this as is.

Yes, that was for my information. It is already merged.

Thanks

  -- Daniel

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