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

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Message-ID: <9726c8c5-5702-4e03-94fc-eaa820f8cdf3@ti.com>
Date: Tue, 22 Apr 2025 12:17:30 -0500
From: Judith Mendez <jm@...com>
To: "Kumar, Udit" <u-kumar1@...com>, Nishanth Menon <nm@...com>
CC: 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 Udit,

On 4/22/25 9:08 AM, Kumar, Udit wrote:
> 
> On 4/22/2025 6:07 PM, 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.
> 
> 
> Thanks , then fix should be extended to sdhci1 as well

sdhci1 and sdhci2 should already be using the defaults: 
https://gist.github.com/jmenti/e280232ae3d5bb5097df7b0f04c85e8a
This change is only needed for eMMC.

~ Judith

> 
> 
>>
>>>> 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.
>>
>>>>> 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(-)
>>>>>
>>>>> [..]