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

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Message-ID: <20260108164225.rtjhnkqzhehnji32@bunkhouse>
Date: Thu, 8 Jan 2026 10:42:25 -0600
From: Nishanth Menon <nm@...com>
To: Vitor Soares <ivitro@...il.com>
CC: "Markus Schneider-Pargmann (TI.com)" <msp@...libre.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>,
	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

On 14:07-20260108, 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?

Side note:

There seem to be multiple issues playing around in U-boot regression.
Please see
https://lore.kernel.org/all/20260108141233.GQ3416603@bill-the-cat/ as
well. There is chunk of discussions on #u-boot irc channel. I'd wait for
U-boot folks to settle things down

-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D
https://ti.com/opensource