[PATCH v6 0/4] Dedicated CLINT timer driver

Anup Patel anup.patel at wdc.com
Fri Jul 24 03:18:18 EDT 2020

The current RISC-V timer driver is convoluted and implements two
distinct timers:
 1. S-mode timer: This is for Linux RISC-V S-mode with MMU. The
    clocksource is implemented using TIME CSR and clockevent device
    is implemented using SBI Timer calls.
 2. M-mode timer: This is for Linux RISC-V M-mode without MMU. The
    clocksource is implemented using CLINT MMIO time register and
    clockevent device is implemented using CLINT MMIO timecmp registers.

This patchset removes clint related code from RISC-V timer driver and
arch/riscv directory. Instead, the series adds a dedicated MMIO based
CLINT driver under drivers/clocksource directory which can be used by
Linux RISC-V M-mode (i.e NoMMU Linux RISC-V).

The patchset is based up Linux-5.8-rc6 and can be found at riscv_clint_v6
branch of: https://github.com/avpatel/linux.git

This series is tested on:
 1. QEMU RV64 virt machine using Linux RISC-V S-mode
 2. QEMU RV32 virt machine using Linux RISC-V S-mode
 3. QEMU RV64 virt machine using Linux RISC-V M-mode (i.e. NoMMU)

Changes since v5:
 - Fixed order of compatible strings in PATCH4
 - Added "additionalProperties: false" in PATCH4
 - Fixed register space size for example DT node in PATCH4

Changes since v4:
 - Rebased series on Linux-5.8-rc6
 - Updated Kconfig option as suggested by Daniel in PATCH2
 - Removed per-CPU registered flag in PATCH2
 - Addressed nit comments from Atish in PATCH2

Changes since v3:
 - Updated commit description of PATCH2
 - Use clint_get_cycles64() in clint_rdtime() of PATCH2
 - Call clockevents_config_and_register() only once for each CPU in
   clint_timer_starting_cpu of PATCH2
 - Select CLINT timer driver from platform Kconfig in PATCH3
 - Fixed 'make dt_binding_check' for PATCH4

Changes since v2:
 - Rebased series on Linux-5.8-rc5
 - Squashed PATCH3 onto PATCH2 to preserve GIT bisectability
 - Moved PATCH4 before PATCH2 to preserve GIT bisectability
 - Replaced CLINT dt-bindings text document with YAML schema
 - Use SiFive CLINT compatible string as per SiFive IP block versioning

Changes since v1:
 - Rebased series on Linux-5.8-rc2
 - Added pr_warn() for case where ipi_ops not available in PATCH1
 - Updated ipi_inject() prototype to use "struct cpumask *" in PATCH1
 - Updated CLINT_TIMER kconfig option to depend on RISCV_M_MODE in PATCH4
 - Added riscv,clint0 compatible string in DT bindings document

Anup Patel (4):
  RISC-V: Add mechanism to provide custom IPI operations
  clocksource/drivers: Add CLINT timer driver
  RISC-V: Remove CLINT related code from timer and arch
  dt-bindings: timer: Add CLINT bindings

 .../bindings/timer/sifive,clint.yaml          |  60 +++++
 arch/riscv/Kconfig                            |   2 +-
 arch/riscv/Kconfig.socs                       |   2 +
 arch/riscv/configs/nommu_virt_defconfig       |   7 +-
 arch/riscv/include/asm/clint.h                |  39 ---
 arch/riscv/include/asm/smp.h                  |  19 ++
 arch/riscv/include/asm/timex.h                |  28 +--
 arch/riscv/kernel/Makefile                    |   2 +-
 arch/riscv/kernel/clint.c                     |  44 ----
 arch/riscv/kernel/sbi.c                       |  14 ++
 arch/riscv/kernel/setup.c                     |   2 -
 arch/riscv/kernel/smp.c                       |  44 ++--
 arch/riscv/kernel/smpboot.c                   |   4 +-
 drivers/clocksource/Kconfig                   |  12 +-
 drivers/clocksource/Makefile                  |   1 +
 drivers/clocksource/timer-clint.c             | 226 ++++++++++++++++++
 drivers/clocksource/timer-riscv.c             |  17 +-
 include/linux/cpuhotplug.h                    |   1 +
 18 files changed, 371 insertions(+), 153 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.yaml
 delete mode 100644 arch/riscv/include/asm/clint.h
 delete mode 100644 arch/riscv/kernel/clint.c
 create mode 100644 drivers/clocksource/timer-clint.c


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