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

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Message-Id: <DFO764ES0FNP.1SUQK9R0EUUDQ@baylibre.com>
Date: Wed, 14 Jan 2026 10:16:33 +0100
From: "Markus Schneider-Pargmann" <msp@...libre.com>
To: "Judith Mendez" <jm@...com>, "Markus Schneider-Pargmann (TI.com)"
 <msp@...libre.com>, "Nishanth Menon" <nm@...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>, "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>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: ti: k3-am62a7-sk: Disable mmc Schmitt
 Trigger

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).

I attached the boot log. It does boot with your patch. Also can this be
an issue with different SD cards?

> Also, are you able to replicate the issue on more than one board? Or is
> this the only board you see the issue on?

I only have one am62a board here.

Best
Markus


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