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

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Message-ID: <a47ca860adb760ad2bf9e3e0d233b0b2b6f73200.camel@gmail.com>
Date: Thu, 08 Jan 2026 15:23:55 +0100
From: Alexander Sverdlin <alexander.sverdlin@...il.com>
To: Vitor Soares <ivitro@...il.com>, "Markus Schneider-Pargmann (TI.com)"
	 <msp@...libre.com>, Nishanth Menon <nm@...com>, Vignesh Raghavendra
	 <vigneshr@...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 Vitor,

On Thu, 2026-01-08 at 14:07 +0000, Vitor Soares wrote:
> On Tue, 2026-01-06 at 17:22 +0100, 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.
> > 
> > Fixes: 5b272127884b ("arm64: dts: ti: k3-pinctrl: Enable Schmitt Trigger by
> > default")
> > Signed-off-by: Markus Schneider-Pargmann (TI.com) <msp@...libre.com>
> > 
> Hi Markus,
> 
> We're seeing a similar issue on Verdin AM62 with U-Boot 2026.01. The
> board has complete SPL boot failure with no output at all.
> 
> This occurs in the same version you bisected (v2026.01 failing).
> Could the Schmitt Trigger changes also affect Verdin AM62?

they do affect AM62, even though not not every HW, I have one HW variant
working properly and one where I observe the problem. Maybe a revert
of 5b272127884b for now would make more sense than just fixing AM62A7.

I unfortunately do not have any reply on this from TI yet.

-- 
Alexander Sverdlin.