linux-kernel - [PATCH v2 0/6] arm64: dts: qcom: msm8916/39: Cleanup/fix UART console pinctrl

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Message-Id: <20250422-msm8916-console-pinctrl-v2-0-f345b7a53c91@linaro.org>
Date: Tue, 22 Apr 2025 13:03:47 +0200
From: Stephan Gerhold <stephan.gerhold@...aro.org>
To: Bjorn Andersson <andersson@...nel.org>, 
 Konrad Dybcio <konradybcio@...nel.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Sam Day <me@...cday.com>, Casey Connolly <casey.connolly@...aro.org>, 
 Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: [PATCH v2 0/6] arm64: dts: qcom: msm8916/39: Cleanup/fix UART
 console pinctrl

At the moment, msm8916/39.dtsi have two inconsistent UART pinctrl templates
that are used by all the boards:

 - &blsp_uart1_default configures all 4 pins (TX, RX, CTS, RTS), some
   boards then limit this to just TX and RX
 - &blsp_uart2_default only configures 2 pins (TX, RX), even though UART2
   also supports CTS/RTS

It's difficult to define a generic pinctrl template for all UART use cases,
since they are quite different in practice. The main use case for most of
the boards is the UART debug console. Unfortunately, the current generic
pinctrl template doesn't work well for that either:

 - We need bias-pull-up for the RX pin to avoid potential garbage at
   runtime when the console UART is not connected, but this may be
   unneeded, unexpected or even unwanted for other UART use cases.

 - U-Boot needs to know which pinctrl to apply during early boot stages, so
   we should specify "bootph-all" for the console UART pinctrl. It doesn't
   make sense to apply this for other UART use cases.

The solution proposed in this series is to abandon the idea that one
generic pinctrl template can fit for all the UART use cases. Instead, add a
new pinctrl specific to the very common console use case, and move the few
other UART use cases directly to the board-specific DT files. This ensures
that people are forced to consider what exactly their UART use case needs
when porting new boards.

Signed-off-by: Stephan Gerhold <stephan.gerhold@...aro.org>
---
Changes in v2:
- Add new line between tx-pins/rx-pins in PATCH 2 (Konrad)
- Squash patches 5,6,8.0 and 7,8.1 (one patch for 8916/8939 dropping the
  generic UART pinctrl templates) (Konrad)
- Link to v1: https://lore.kernel.org/r/20250415-msm8916-console-pinctrl-v1-0-a1d33ea994b9@linaro.org

---
Stephan Gerhold (6):
      arm64: dts: qcom: msm8916/39: Move UART pinctrl to board files
      arm64: dts: qcom: msm8916/39: Introduce new UART console pinctrl
      arm64: dts: qcom: msm8919/39: Use UART2 console pinctrl where appropriate
      arm64: dts: qcom: msm8916-motorola: Use UART1 console pinctrl
      arm64: dts: qcom: msm8916: Drop generic UART pinctrl templates
      arm64: dts: qcom: msm8939: Drop generic UART pinctrl templates

 arch/arm64/boot/dts/qcom/apq8016-sbc.dts           | 21 +++++++++
 .../boot/dts/qcom/apq8016-schneider-hmibsc.dts     | 41 ++++++++++++++--
 arch/arm64/boot/dts/qcom/apq8039-t2.dts            | 28 +++++++----
 arch/arm64/boot/dts/qcom/msm8916-acer-a1-724.dts   |  3 ++
 .../boot/dts/qcom/msm8916-alcatel-idol347.dts      |  3 ++
 arch/arm64/boot/dts/qcom/msm8916-asus-z00l.dts     |  3 ++
 arch/arm64/boot/dts/qcom/msm8916-gplus-fl8005a.dts |  3 ++
 arch/arm64/boot/dts/qcom/msm8916-huawei-g7.dts     |  3 ++
 arch/arm64/boot/dts/qcom/msm8916-lg-c50.dts        |  3 ++
 arch/arm64/boot/dts/qcom/msm8916-lg-m216.dts       |  3 ++
 .../boot/dts/qcom/msm8916-longcheer-l8150.dts      |  3 ++
 .../boot/dts/qcom/msm8916-longcheer-l8910.dts      |  3 ++
 .../boot/dts/qcom/msm8916-motorola-common.dtsi     | 11 ++---
 arch/arm64/boot/dts/qcom/msm8916-mtp.dts           |  3 ++
 .../dts/qcom/msm8916-samsung-a2015-common.dtsi     |  3 ++
 .../dts/qcom/msm8916-samsung-fortuna-common.dtsi   |  3 ++
 .../boot/dts/qcom/msm8916-samsung-gt5-common.dtsi  |  3 ++
 .../boot/dts/qcom/msm8916-samsung-j5-common.dtsi   |  3 ++
 .../boot/dts/qcom/msm8916-samsung-serranove.dts    |  3 ++
 arch/arm64/boot/dts/qcom/msm8916-ufi.dtsi          |  3 ++
 .../boot/dts/qcom/msm8916-wingtech-wt865x8.dtsi    |  3 ++
 .../boot/dts/qcom/msm8916-wingtech-wt88047.dts     |  3 ++
 arch/arm64/boot/dts/qcom/msm8916.dtsi              | 55 ++++++++++++++--------
 arch/arm64/boot/dts/qcom/msm8939-huawei-kiwi.dts   |  3 ++
 .../boot/dts/qcom/msm8939-longcheer-l9100.dts      |  3 ++
 arch/arm64/boot/dts/qcom/msm8939-samsung-a7.dts    |  3 ++
 .../boot/dts/qcom/msm8939-wingtech-wt82918.dtsi    |  3 ++
 arch/arm64/boot/dts/qcom/msm8939.dtsi              | 54 +++++++++++++--------
 28 files changed, 217 insertions(+), 59 deletions(-)
---
base-commit: 39155a896925c3af2156ad61e821aa9fa5a1dbdb
change-id: 20250411-msm8916-console-pinctrl-069fd22abedd

Best regards,
-- 
Stephan Gerhold <stephan.gerhold@...aro.org>