linux-kernel - Re: [PATCH v2 3/4] arm64: dts: ti: k3-am62p: add opp frequencies

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Message-ID: <571daac8-a5a4-4cc6-b95c-68cd7e0eb924@ti.com>
Date: Tue, 27 Aug 2024 09:55:36 +0530
From: Vignesh Raghavendra <vigneshr@...com>
To: Bryan Brattlof <bb@...com>, Dhruva Gole <d-gole@...com>
CC: Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        Rob Herring
	<robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] arm64: dts: ti: k3-am62p: add opp frequencies



On 26/08/24 21:41, Bryan Brattlof wrote:
> On August 26, 2024 thus sayeth Dhruva Gole:
>> Hi Bryan,
>>
>> On Aug 23, 2024 at 16:54:30 -0500, Bryan Brattlof wrote:
>>> ONe power management technique available to the Cortex-A53s is their
>>
>> s/ONe/One
>>
>>> ability to dynamically scale their frequency across the device's
>>> Operating Performance Points (OPP)
>>>
>>> The OPPs available for the Cortex-A53s on the AM62Px can vary based on
>>> the silicon variant used. The SoC variant is encoded into the
>>> WKUP_MMR0_WKUP0_CTRL_MMR0_JTAG_USER_ID register which is used to limit
>>> the OPP entries the SoC supports. A table of all these variants can be
>>> found in its data sheet[0] for the AM62Px processor family.
>>
>> Error 404! Not found [0] ;)
>>
> 
> Oops. I'll fix these up
> 
>>>
>>> Add the OPP table into the SoC's ftdi file along with the syscon node to
>>
>> What is ftdi?
> 
> FTDI is a chip, what I tried to type out was fdti or Flattened Device 
> Tree Includes :)
> 
>>
>>> describe the WKUP_MMR0_WKUP0_CTRL_MMR0_JTAG_USER_ID register to detect
>>> the SoC variant.
>>>
>>> Signed-off-by: Bryan Brattlof <bb@...com>
>>> ---
>>>  .../boot/dts/ti/k3-am62p-j722s-common-wakeup.dtsi  |  5 +++
>>>  arch/arm64/boot/dts/ti/k3-am62p5.dtsi              | 47 ++++++++++++++++++++++
>>>  2 files changed, 52 insertions(+)
>>>
>>> diff --git a/arch/arm64/boot/dts/ti/k3-am62p-j722s-common-wakeup.dtsi b/arch/arm64/boot/dts/ti/k3-am62p-j722s-common-wakeup.dtsi
>>> index 315d0092e7366..6f32135f00a55 100644
>>> --- a/arch/arm64/boot/dts/ti/k3-am62p-j722s-common-wakeup.dtsi
>>> +++ b/arch/arm64/boot/dts/ti/k3-am62p-j722s-common-wakeup.dtsi
>>> @@ -20,6 +20,11 @@ chipid: chipid@14 {
>>>  			bootph-all;
>>>  		};
>>>  
>>> +		opp_efuse_table: syscon@18 {
>>> +			compatible = "ti,am62-opp-efuse-table", "syscon";
>>
>> Huh, curious why I don't see this particular compatible in am62 itself..
>> Also, I am still not clear where this discussion got left off: (If it's
>> related)
>> https://lore.kernel.org/all/5chxjwybmsxq73pagtlw4zr2asbtxov7ezrpn5j37cr77bmepa@fejdlxomfgae/
>>
>> In AM625, I see
>> k3-am625.dtsi:111: col 14: syscon = <&wkup_conf>;
>>
>> But the approach you've used here seems different. Is there a
>> justification given on which one should be used/why somewhere that I can
>> refer?
> 
> Labeling the entire &wkup_conf as a syscon node is kinda abusing what 
> the syscon node is used for. There are a lot of things inside that 
> WKUP_CTRL_MMR that do not belong under the miscellaneous registers 
> category. For the 62A and 62P we've chosen to label &wkup_conf as a bus 
> with little syscon sub-nodes inside of it.  
> 
> I don't think the discussion[0] ever finalized but we started going that 
> direction with new SoCs, looks like the older SoCs never received the 
> cleanup.

This patch seems to be in the right direction. Marking entire wkup_conf
as "syscon", "simple-mfd" is wrong and needs to be addressed in
k3-am62-wakeup.dtsi similar to how other child-nodes in wkup_conf are
implemented in same file.

[...]

-- 
Regards
Vignesh