linux-kernel - [PATCH] arm64: dts: ti: k3-pinctrl: Enable Schmitt Trigger by default

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Message-ID: <20250701105437.3539924-1-alexander.sverdlin@siemens.com>
Date: Tue,  1 Jul 2025 12:54:35 +0200
From: "A. Sverdlin" <alexander.sverdlin@...mens.com>
To: devicetree@...r.kernel.org
Cc: Alexander Sverdlin <alexander.sverdlin@...mens.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>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] arm64: dts: ti: k3-pinctrl: Enable Schmitt Trigger by default

From: Alexander Sverdlin <alexander.sverdlin@...mens.com>

Switch Schmitt Trigger functions for PIN_INPUT* macros by default. This is
HW PoR configuration, the slew rate requirements without ST enabled are
pretty tough for these devices. We've noticed spurious GPIO interrupts even
with noise-free edges but not meeting slew rate requirements (3.3E+6 V/s
for 3.3v LVCMOS).

It's not obvious why one might want to disable the PoR-enabled ST on any
pin. Just enable it by default. As it's not possible to provide OR-able
macros to disable the ST, shall anyone require it, provide a set of
new macros with _NOST suffix.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...mens.com>
---
This patch could be considered a v2 of [1] but the subject has been changed.

[1] Link: https://lore.kernel.org/all/20250627131332.2806026-1-alexander.sverdlin@siemens.com/

 arch/arm64/boot/dts/ti/k3-pinctrl.h | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/boot/dts/ti/k3-pinctrl.h b/arch/arm64/boot/dts/ti/k3-pinctrl.h
index cac7cccc11121..38590188dd51c 100644
--- a/arch/arm64/boot/dts/ti/k3-pinctrl.h
+++ b/arch/arm64/boot/dts/ti/k3-pinctrl.h
@@ -8,6 +8,7 @@
 #ifndef DTS_ARM64_TI_K3_PINCTRL_H
 #define DTS_ARM64_TI_K3_PINCTRL_H
 
+#define ST_EN_SHIFT		(14)
 #define PULLUDEN_SHIFT		(16)
 #define PULLTYPESEL_SHIFT	(17)
 #define RXACTIVE_SHIFT		(18)
@@ -19,6 +20,10 @@
 #define DS_PULLUD_EN_SHIFT	(27)
 #define DS_PULLTYPE_SEL_SHIFT	(28)
 
+/* Schmitt trigger configuration */
+#define ST_DISABLE		(0 << ST_EN_SHIFT)
+#define ST_ENABLE		(1 << ST_EN_SHIFT)
+
 #define PULL_DISABLE		(1 << PULLUDEN_SHIFT)
 #define PULL_ENABLE		(0 << PULLUDEN_SHIFT)
 
@@ -32,9 +37,13 @@
 #define PIN_OUTPUT		(INPUT_DISABLE | PULL_DISABLE)
 #define PIN_OUTPUT_PULLUP	(INPUT_DISABLE | PULL_UP)
 #define PIN_OUTPUT_PULLDOWN	(INPUT_DISABLE | PULL_DOWN)
-#define PIN_INPUT		(INPUT_EN | PULL_DISABLE)
-#define PIN_INPUT_PULLUP	(INPUT_EN | PULL_UP)
-#define PIN_INPUT_PULLDOWN	(INPUT_EN | PULL_DOWN)
+#define PIN_INPUT		(INPUT_EN | ST_ENABLE | PULL_DISABLE)
+#define PIN_INPUT_PULLUP	(INPUT_EN | ST_ENABLE | PULL_UP)
+#define PIN_INPUT_PULLDOWN	(INPUT_EN | ST_ENABLE | PULL_DOWN)
+/* Input configurations with Schmitt Trigger disabled */
+#define PIN_INPUT_NOST		(INPUT_EN | PULL_DISABLE)
+#define PIN_INPUT_PULLUP_NOST	(INPUT_EN | PULL_UP)
+#define PIN_INPUT_PULLDOWN_NOST	(INPUT_EN | PULL_DOWN)
 
 #define PIN_DEBOUNCE_DISABLE	(0 << DEBOUNCE_SHIFT)
 #define PIN_DEBOUNCE_CONF1	(1 << DEBOUNCE_SHIFT)
-- 
2.50.0