linux-kernel - [PATCH v6 0/2] riscv: Use GCR.U timer device as clocksource

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Message-Id: <20250806-riscv-time-mmio-v6-0-2df0e8219998@htecgroup.com>
Date: Wed, 06 Aug 2025 14:26:38 +0200
From: Aleksa Paunovic via B4 Relay <devnull+aleksa.paunovic.htecgroup.com@...nel.org>
To: Daniel Lezcano <daniel.lezcano@...aro.org>, 
 Thomas Gleixner <tglx@...utronix.de>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Alexandre Ghiti <alex@...ti.fr>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-riscv@...ts.infradead.org, 
 Djordje Todorovic <djordje.todorovic@...cgroup.com>, 
 Aleksa Paunovic <aleksa.paunovic@...cgroup.com>, 
 Conor Dooley <conor.dooley@...rochip.com>
Subject: [PATCH v6 0/2] riscv: Use GCR.U timer device as clocksource

This series adds bindings for the GCR.U timer device and corresponding
driver support. Accessing the memory mapped mtime register in the GCR.U
region should be faster than trapping to M mode each time the timer
needs to be read.

Signed-off-by: Aleksa Paunovic <aleksa.paunovic@...cgroup.com>
---
Changes in v6:
- Rename mti,gcru to mips,p8700-gcru
- Link to v5: https://lore.kernel.org/r/20250711-riscv-time-mmio-v5-0-9ed1f825ad5e@htecgroup.com

Changes in v5:
- Fixed build issues on 32-bit RISC-V and sparse warnings
- Remove clint_time_val and clint.h, replace with riscv_time_val
- Depend on RISCV_TIMER in Kconfig
Changes in v4:
- Remove "select" from mti,gcru.yaml.
- Refactor the driver to use function pointers instead of static keys.

Previous versions:
v1: https://lore.kernel.org/lkml/20241227150056.191794-1-arikalo@gmail.com/#t
v2: https://lore.kernel.org/linux-riscv/20250409143816.15802-1-aleksa.paunovic@htecgroup.com/
v3: https://lore.kernel.org/linux-riscv/DU0PR09MB61968695A2A3146EE83B7708F6BA2@DU0PR09MB6196.eurprd09.prod.outlook.com/
v4: https://lore.kernel.org/r/20250514-riscv-time-mmio-v4-0-cb0cf2922d66@htecgroup.com
v5: https://lore.kernel.org/r/20250711-riscv-time-mmio-v5-0-9ed1f825ad5e@htecgroup.com

---
Aleksa Paunovic (2):
      dt-bindings: timer: mips,p8700-gcru
      riscv: Allow for riscv-clock to pick up mmio address.

 .../devicetree/bindings/timer/mips,p8700-gcru.yaml | 38 +++++++++++++
 arch/riscv/include/asm/clint.h                     | 26 ---------
 arch/riscv/include/asm/timex.h                     | 63 ++++++++++++----------
 drivers/clocksource/Kconfig                        | 12 +++++
 drivers/clocksource/timer-clint.c                  | 20 ++++---
 drivers/clocksource/timer-riscv.c                  | 34 ++++++++++++
 6 files changed, 128 insertions(+), 65 deletions(-)
---
base-commit: 038d61fd642278bab63ee8ef722c50d10ab01e8f
change-id: 20250424-riscv-time-mmio-5628e0fca8af

Best regards,
-- 
Aleksa Paunovic <aleksa.paunovic@...cgroup.com>