linux-kernel - [PATCH v2 0/2] serial: 8250: omap: Add wakeup support

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Message-ID: <20250910-uart-daisy-chain-8250-omap-v2-0-e90d44c1a9ac@ti.com>
Date: Wed, 10 Sep 2025 16:23:30 -0500
From: Kendall Willis <k-willis@...com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby
	<jirislaby@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski
	<krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Vignesh Raghavendra
	<vigneshr@...com>
CC: <linux-kernel@...r.kernel.org>, <linux-serial@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <d-gole@...com>, <vishalm@...com>,
        <sebin.francis@...com>, <msp@...libre.com>, <khilman@...libre.com>,
        <a-kaur@...com>, <andriy.shevchenko@...ux.intel.com>,
        <yujiaoliang@...o.com>, <b-liu@...com>, <u.kleine-koenig@...libre.com>,
        Kendall Willis
	<k-willis@...com>
Subject: [PATCH v2 0/2] serial: 8250: omap: Add wakeup support

This series adds wakeup support for the serial 8250_omap driver. On the
TI K3 AM62 family of devices, the UARTs are able to wakeup the system
from various low power modes by using I/O daisy-chaining.

The wakeup functionality is implemented by adding the pinctrl state
'wakeup' in which specific flags are set on the pins to enable wakeup
via I/O daisy-chain. If the 'wakeup' pinctrl state exists for the serial
device, the 'wakeup' pinctrl state is selected on suspend. Upon resume,
the pinctrl 'default' state is selected.

The commits "dt-bindings: serial: 8250_omap: Add wakeup pinctrl state"
and "serial: 8250: omap: Support wakeup pinctrl state on suspend" were
picked from this series [1]. The commit "dt-bindings: serial: 8250_omap:
Add wakeup pinctrl state" was updated to follow the structure of a
similar patch [2] by Markus for the m_can driver. The commit "serial:
8250: omap: Support wakeup pinctrl state on suspend" was updated to only
include s2ram functionality instead of a poweroff state.

Implementation
--------------
This series is intended to be implemented along with the following
series. This patch has no dependencies on any of the other series:

1. "pmdomain: ti_sci: Handle wakeup constraint if device has pinctrl
   wakeup state" [3]: Patch which skips setting constraints for wakeup
   sources that use pinctrl state 'wakeup'.

2. "serial: 8250: omap: Add wakeup support" (this series): Implements
   wakeup from the UARTs for TI K3 SoCs

3. "arm64: dts: ti: k3-am62: Support Main UART wakeup" [4]: Implements
   the functionality to wakeup the system from the Main UART

Testing
-------
Tested on a AM62P SK EVM board with all series and dependencies
implemented. Suspend/resume verified with the Main UART wakeup source
by entering a keypress on the console.

This github branch [5] has all the necessary patches to test the series
using linux-next.

Links
-----
[1] https://lore.kernel.org/all/20240523075819.1285554-1-msp@baylibre.com/
[2] https://lore.kernel.org/all/20250820-topic-mcan-wakeup-source-v6-12-v9-1-0ac13f2ddd67@baylibre.com/
[3] https://github.com/kwillis01/linux/tree/b4/uart-daisy-chain-pmdomain
[4] https://github.com/kwillis01/linux/tree/b4/uart-daisy-chain-dts
[5] https://github.com/kwillis01/linux/tree/uart-daisy-chain

Previous Versions
-----------------
v1: https://lore.kernel.org/all/20250904212455.3729029-1-k-willis@ti.com/

Changes from v1 to v2:
 - Drop patch for updated wakeup-source binding
 - Update dt binding for pinctrl to only use either default or sleep
   states and change commit message to reflect the change

base-commit: 4ac65880ebca1b68495bd8704263b26c050ac010
---
Markus Schneider-Pargmann (2):
      dt-bindings: serial: 8250_omap: Add wakeup pinctrl state
      serial: 8250: omap: Support wakeup pinctrl state on suspend

 .../devicetree/bindings/serial/8250_omap.yaml      | 16 ++++++++++
 drivers/tty/serial/8250/8250_omap.c                | 36 ++++++++++++++++++++++
 2 files changed, 52 insertions(+)
---
base-commit: 5f540c4aade9f1d58fb7b9490b4b7d5214ec9746
change-id: 20250910-uart-daisy-chain-8250-omap-3649ec6a7155

Best regards,
-- 
Kendall Willis <k-willis@...com>