linux-kernel - [PATCH v2 0/2] Add Realtek System Timer driver

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Message-ID: <20251114090448.285685-1-haowen.ting@realtek.com>
Date: Fri, 14 Nov 2025 17:04:46 +0800
From: Hao-Wen Ting <haowen.ting@...ltek.com>
To: <daniel.lezcano@...aro.org>, <tglx@...utronix.de>
CC: <jinn.cheng@...ltek.com>, <edwardwu@...ltek.com>, <phelic@...ltek.com>,
        <shawn.huang724@...ltek.com>, <haowen.ting@...ltek.com>,
        <cy.huang@...ltek.com>, <james.tai@...ltek.com>, <cylee12@...ltek.com>,
        <phinex@...ltek.com>, <conor+dt@...nel.org>, <krzk+dt@...nel.org>,
        <robh@...nel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <stanley_chang@...ltek.com>
Subject: [PATCH v2 0/2] Add Realtek System Timer driver

Changes v2:
PATCH 1/2
- Add full name 'system timer' to description
- Remove redundant commit messages
- Clarify compatible strings for specific verified SoCs
- Remove redundant reg and interrupts description sentences
- Use generic node name in example
PATCH 2/2
- Correct MAINTAINERS to alphabetical order
- Update Kconfig: switch dependency to ARM/ARM64
- Remove redundant pr_info output

This patch series adds support for the Realtek SYSTIMER, a 64-bit timer
that serves as a tick broadcast timer on Realtek SoCs.

On Realtek platforms, CPUs can enter deep idle states (C-states) where
local timers are stopped and powered off. Without a global tick broadcast
timer, one CPU must remain awake to wake up the others, preventing all CPUs
from entering deep idle simultaneously and limiting power savings.

The Realtek SYSTIMER remains active during deep idle states, allowing all
CPUs to enter power-cut idle states simultaneously. This significantly
reduces overall power consumption while maintaining proper tick broadcast
functionality.

The systimer hardware for both RTD1625 and RTD1635 SoCs has identical register
layout and IRQ configuration. The driver therefore matches both compatibles
without special handling and has been tested on both platforms.

Technical details:
- 64-bit timer operating at 1MHz fixed frequency
- Supports oneshot mode for tick broadcast
- Uses standard TIMER_OF framework and Device Tree integration
- Remains active during CPU power-down states

Testing:
- Verify the functionality of tick broadcast timer on both RTD1625 and RTD1635
SoCs.
- Verify the power consumption reduction on RTD1625 Soc in deep idle scenarios

Patch organization:
Patch 1/2: Device Tree binding documentation
Patch 2/2: Clocksource driver implementation

Best regards,
Hao-Wen Ting

Hao-Wen Ting (2):
  dt-bindings: timer: Add Realtek SYSTIMER binding
  clocksource: Add Realtek systimer as tick broadcast driver

 .../bindings/timer/realtek,systimer.yaml      |  48 +++++
 MAINTAINERS                                   |   5 +
 drivers/clocksource/Kconfig                   |  10 +
 drivers/clocksource/Makefile                  |   1 +
 drivers/clocksource/timer-realtek.c           | 172 ++++++++++++++++++
 5 files changed, 236 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/timer/realtek,systimer.yaml
 create mode 100644 drivers/clocksource/timer-realtek.c


base-commit: 948b99877bf5a1cd58bee930e455b7574daba5c3
-- 
2.34.1