linux-kernel - [PATCH 0/7] dts: amlogic: enable UART RX and TX pull up by default

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Message-ID: <20250329185855.854186-1-martin.blumenstingl@googlemail.com>
Date: Sat, 29 Mar 2025 19:58:48 +0100
From: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To: linux-amlogic@...ts.infradead.org
Cc: linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org,
	jbrunet@...libre.com,
	khilman@...libre.com,
	neil.armstrong@...aro.org,
	christianshewitt@...il.com,
	Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [PATCH 0/7] dts: amlogic: enable UART RX and TX pull up by default

On the LibreELEC forum there have been reports that Odroid-C2 does not
boot when UART is left disconnected [0]. It turns out that this can be
solved by enabling the SoCs pull-up resistor on the UART RX and TX
pads [1].
It's not clear whether that specific Odroid-C2 board has a broken
resistor, the resistor is not populated (either by accident or on
purpose) or if there's another reason.

Testing on an SM1 X96-Air shows that pull-ups being enabled on UART
RX and TX is actually the default (either set in vendor u-boot or an
actual hardware default).

This series enables the UART RX and TX pull up resistors in the
default pin configuration on all supported SoCs.

Testing has been done on:
- GXBB Odroid-C1 on u-boot by a user in the LibreELEC forums [2]
- Meson8b Odroid-C1 on Linux (with vendor u-boot)
- SM1 X96-Air on Linux (with vendor u-boot)

Please include this early so the various CI systems can test these
patches.


[0] https://forum.libreelec.tv/thread/28586-odroid-c2-gxbb-s905-and-le-11-06-or-12-does-not-boot/?postID=195481#post195481
[1] https://forum.libreelec.tv/thread/28586-odroid-c2-gxbb-s905-and-le-11-06-or-12-does-not-boot/?postID=195667#post195667
[2] https://forum.libreelec.tv/thread/28586-odroid-c2-gxbb-s905-and-le-11-06-or-12-does-not-boot/?postID=195674#post195674


Martin Blumenstingl (7):
  ARM: dts: amlogic: meson8: enable UART RX and TX pull up by default
  ARM: dts: amlogic: meson8b: enable UART RX and TX pull up by default
  arm64: dts: amlogic: gxbb: enable UART RX and TX pull up by default
  arm64: dts: amlogic: gxl: enable UART RX and TX pull up by default
  arm64: dts: amlogic: g12: enable UART RX and TX pull up by default
  arm64: dts: amlogic: axg: enable UART RX and TX pull up by default
  arm64: dts: amlogic: a1: enable UART RX and TX pull up by default

 arch/arm/boot/dts/amlogic/meson8.dtsi             |  4 ++--
 arch/arm/boot/dts/amlogic/meson8b.dtsi            |  4 ++--
 arch/arm64/boot/dts/amlogic/meson-a1.dtsi         |  1 +
 arch/arm64/boot/dts/amlogic/meson-axg.dtsi        | 12 ++++++------
 arch/arm64/boot/dts/amlogic/meson-g12-common.dtsi | 10 +++++-----
 arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi       | 10 +++++-----
 arch/arm64/boot/dts/amlogic/meson-gxl.dtsi        | 12 ++++++------
 7 files changed, 27 insertions(+), 26 deletions(-)

-- 
2.49.0