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

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Message-ID: <96bebaef0d608d4d7bdbaf0fbabe3b1835b01400.camel@gmail.com>
Date: Wed, 07 Jan 2026 15:23:07 +0100
From: Alexander Sverdlin <alexander.sverdlin@...il.com>
To: Markus Schneider-Pargmann <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>
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 Markus,

short update from my side:

> > I think we would need to discuss this with TI via our FAE, because the change
> > in question has both been discussed with former FAE and the technical team
> > behind, and adopted in TI SDK.

I've reported this to the new FAE at TI, let's see how quickly relevant
people at TI could look into it... I unfortunately don't have access to
AM62A7 HW, but I've re-tested SD card on our AM623-based HW and I see no
issues under Linux.

> 
> > > +			AM62AX_IOPAD(0x23c, PIN_INPUT_NOST, 0) /* (A21) MMC1_CMD */
> > > +			AM62AX_IOPAD(0x234, PIN_INPUT_NOST, 0) /* (B22) MMC1_CLK */
> > > +			AM62AX_IOPAD(0x230, PIN_INPUT_NOST, 0) /* (A22) MMC1_DAT0 */
> > > +			AM62AX_IOPAD(0x22c, PIN_INPUT_NOST, 0) /* (B21) MMC1_DAT1 */
> > > +			AM62AX_IOPAD(0x228, PIN_INPUT_NOST, 0) /* (C21) MMC1_DAT2 */
> > > +			AM62AX_IOPAD(0x224, PIN_INPUT_NOST, 0) /* (D22) MMC1_DAT3 */
> > > +			AM62AX_IOPAD(0x240, PIN_INPUT_NOST, 0) /* (D17) MMC1_SDCD */
> 
> My board is setup to boot from SD card for easier u-boot testing. So
> only the mmc1 is relevant for my setup. I just tested which pins need
> NOST here for the boot to work, all DAT pins need the NOST variants,
> otherwise it does not boot here. Not sure if this is just my board or it
> fails on other boards as well.

Thanks for checking this!
I'm curious: is it only U-Boot issue? Does the card work properly if you
still have ST enabled in Linux?

I'm a bit hesitatnt to revert the ST on these (or any other) pins without
understanding what's going on in HW, because from all our discussions with
TI we've concluded that ST shall be used on all pins without any drawbacks.

Getting this back to TI will also help them to figure out the HW requirements
and document them better.

I'll keep you informed, shall I have any new info...

-- 
Alexander Sverdlin.