linux-kernel - Re: [PATCH 2/3] arm64: dts: ti: k3-j7200: Add the supported frequencies for A72

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Message-ID: <6ec58e9c-0661-cb97-b133-cdcc40d4e4f0@ti.com>
Date:   Thu, 10 Aug 2023 19:49:28 +0530
From:   "Kumar, Udit" <u-kumar1@...com>
To:     Nishanth Menon <nm@...com>
CC:     Apurva Nandan <a-nandan@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Rafael J Wysocki <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-pm@...r.kernel.org>, Keerthy J <j-keerthy@...com>,
        <u-kumar1@...com>
Subject: Re: [PATCH 2/3] arm64: dts: ti: k3-j7200: Add the supported
 frequencies for A72


On 8/10/2023 6:23 PM, Nishanth Menon wrote:
> On 17:23-20230810, Kumar, Udit wrote:
> [..]
>>>> +		opp1-750000000 {
>>>> +			opp-hz = /bits/ 64 <750000000>;
>>>>    		};
>>>>    	};
>>>> -- 
>>>> 2.34.1
>>>>
>>> [..]
>>> This wont work:
>>>
>>> a) in u-boot's falcon boot mode and puts unrelated responsibility to
>>> bootloader (u-boot is not the only bootloader in the party here).
>>> b) Further, the reason for doing the opp detection in the kernel is
>>> due to the severity of consequence of attempting to run a lower rated
>>> chip at higher frequency - PoH (Power on Hours) or physical damage can
>>> result.
>>> c) Finally, in a virtualized environment: TISCI will get DM (Device
>>> Manager) to arbitrate between the each of the VM's request, but if
>>> the VM's are'nt self sufficient, we will have DM making wrong choices
>>> resulting in (b) condition again.
>>>
>>> This is the reason why drivers/cpufreq/ti-cpufreq.c exists and all SoCs
>>> that have OPPs from TI is handled in the kernel itself.

Thanks to pointing to this driver.