linux-kernel - Re: [PATCH v2 1/5] arm64: dts: ti: k3-am6*: Set eMMC clock parents to default

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Message-ID: <965765c3-324f-4621-bbd6-b55f6eb44d1d@ti.com>
Date: Fri, 25 Apr 2025 17:01:55 -0500
From: Judith Mendez <jm@...com>
To: Nishanth Menon <nm@...com>
CC: "Kumar, Udit" <u-kumar1@...com>, Vignesh Raghavendra <vigneshr@...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>, Moteen Shah <m-shah@...com>
Subject: Re: [PATCH v2 1/5] arm64: dts: ti: k3-am6*: Set eMMC clock parents to
 default

Hi Nishanth,

On 4/22/25 7:37 AM, Nishanth Menon wrote:
> On 09:36-20250421, Judith Mendez wrote:
>> Hi Udit,
>>
>> On 4/19/25 10:00 AM, Kumar, Udit wrote:
>>>
>>> On 4/18/2025 5:00 AM, Judith Mendez wrote:
>>>> Set eMMC clock parents to the defaults which is MAIN_PLL0_HSDIV5_CLKOUT
>>>> for eMMC. This change is necessary since DM is not implementing the
>>>> correct procedure to switch PLL clock source for eMMC and we have a
>>>> non-glich-free mux. To remove any potential issues, lets switch back to
>>>> the defaults.
>>>
>>> IMO, we need to fix DM  if not then documentation [0] .
>>
>> DM cannot be fixed for only one IP and documentation says what clock
>> parents are supported, it does not have to say what are the issues
>> that come with using a specific clock parent.
> 
> As I understand the arasan IP requirement is that the IP must be held in
> reset while the clock is switched, which is not reasonable to implement
> given decoupled systems like DM and Linux OS.
> 
>>
>>>
>>> Then only this patch is ok because as per document [0]
>>>
>>> removed clock by this patch is valid parent for eMMC.
>>
>> The clock parent currently set is a valid parent, but we have non-
>> glitch-free muxes and to avoid any potential issues with these, we
>> should switch back to the defaults. It seems like we randomly switched
>> from the default for no good reason and it has been copy paste per
>> platforms since then, so we are switching back to the defaults now.
>>
>> ~ Judith
>>
>>>
>>> [0] https://software-dl.ti.com/tisci/esd/latest/5_soc_doc/j722s/clocks.html
>>>
>>> Thanks
>>>
>>> Udit
>>>
>>>>
>>>> Fixes: c37c58fdeb8a ("arm64: dts: ti: k3-am62: Add more peripheral
>>>> nodes")
>>>> Fixes: d3ae4e8d8b6a ("arm64: dts: ti: k3-am62a-main: Add sdhci0
>>>> instance")
>>>> Fixes: b5080c7c1f7e ("arm64: dts: ti: k3-am62p: Add nodes for more IPs")
> 
> Please follow ./Documentation/process/stable-kernel-rules.rst - this is
> easier to backport if these were to be split into 3 different patches.
> Please do not forget to add Cc: stable@...r.kernel.org as per the rules
> as well.

Understood, will split-up this series and respin, thanks.

~ Judith

> 
>>>> Signed-off-by: Judith Mendez <jm@...com>
>>>> ---
>>>>    arch/arm64/boot/dts/ti/k3-am62-main.dtsi               | 2 --
>>>>    arch/arm64/boot/dts/ti/k3-am62a-main.dtsi              | 2 --
>>>>    arch/arm64/boot/dts/ti/k3-am62p-j722s-common-main.dtsi | 2 --
>>>>    3 files changed, 6 deletions(-)
>>>>
>>>> [..]
>>
>