linux-kernel - Re: [PATCH] arm64: dts: ti: k3-am62a7-sk: Disable mmc Schmitt Trigger

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Message-Id: <DG59D7WGM35A.1WNIIMNCQ8U3C@baylibre.com>
Date: Tue, 03 Feb 2026 11:35:10 +0100
From: "Markus Schneider-Pargmann" <msp@...libre.com>
To: "Judith Mendez" <jm@...com>, "Markus Schneider-Pargmann"
 <msp@...libre.com>, "Alexander Sverdlin" <alexander.sverdlin@...il.com>
Cc: "Vishal Mahaveer" <vishalm@...com>, "Kevin Hilman"
 <khilman@...libre.com>, "Dhruva Gole" <d-gole@...com>, "Sebin Francis"
 <sebin.francis@...com>, "Kendall Willis" <k-willis@...com>, "Akashdeep
 Kaur" <a-kaur@...com>, <linux-arm-kernel@...ts.infradead.org>,
 <devicetree@...r.kernel.org>, "Conor Dooley" <conor+dt@...nel.org>,
 "Krzysztof Kozlowski" <krzk+dt@...nel.org>, "Rob Herring"
 <robh@...nel.org>, <linux-kernel@...r.kernel.org>, "Nishanth Menon"
 <nm@...com>, "Vignesh Raghavendra" <vigneshr@...com>, "Tero Kristo"
 <kristo@...nel.org>
Subject: Re: [PATCH] arm64: dts: ti: k3-am62a7-sk: Disable mmc Schmitt
 Trigger

Hi Judith,

On Wed Jan 14, 2026 at 11:04 PM CET, Judith Mendez wrote:
> Hi Markus,
>
> On 1/14/26 3:16 AM, Markus Schneider-Pargmann wrote:
>> Hi Judith,
>> 
>> On Tue Jan 13, 2026 at 1:29 AM CET, Judith Mendez wrote:
>>> On 1/6/26 10:22 AM, Markus Schneider-Pargmann (TI.com) wrote:
>>>> Remove Schmitt Trigger from mmc pins. With Schmitt Trigger enabled
>>>> u-boot SPL is not able to read u-boot from mmc:
>>>>
>>>>       Trying to boot from MMC2
>>>>       Error reading cluster
>>>>       spl_load_image_fat: error reading image u-boot.img, err - -22
>>>>       Error: -22
>>>>       SPL: Unsupported Boot Device!
>>>>       SPL: failed to boot from all boot devices
>>>>       ### ERROR ### Please RESET the board ###
>>>>
>>>> I bisected this issue between u-boot v2025.10 and v2026.01 and found the
>>>> devicetree merge to be the problem. At a closer look I found the
>>>> k3-pinctrl.h changes. Disabling the Schmitt Trigger fixes the u-boot SPL
>>>> failure to read from mmc.
>>>
>>> I have tested 4 AM62A SK boards and I cannot replicate the issue
>>> you are seeing. I do not see an issue with Schmitt Trigger in U-boot
>>> nor Linux /:
>> 
>> Thanks for testing.
>> 
>>> Can you please run a quick tap sweep on MMC1 and MMC0 interfaces like
>>> so? https://gist.github.com/jmenti/f4a73a8323e44bf717c6d2c528c499ca
>>>
>>> This will give me an idea if whether we should be talking about
>>> revisiting characterization with ST_ENA=1.
>> 
>> The patch was a bit broken, but I think I managed to apply it to
>> v2026.01 as it was supposed to be. (master currently doesn't boot even
>> SPL, I don't have time right now to debug that).
>
> as Nishanth, mentioned, master is missing two patches [0][1]
>
>> 
>> I attached the boot log. It does boot with your patch. Also can this be
>> an issue with different SD cards?
>
> Something does not quite add up,
>
> Can you try the following 2 commands?
>
> # mmc dev 1
> # md.w 0xfa0810c

Finally here is the output from boot and executing these commands. I am
now on v2026.04-rc1 with your sweep patch.

Best
Markus


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