linux-kernel - Re: [PATCH v3 0/4] Dedicated CLINT timer driver

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Date:   Wed, 15 Jul 2020 16:47:34 +0200
From:   Emil Renner Berthing <emil.renner.berthing@...il.com>
To:     Anup Patel <anup.patel@....com>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Rob Herring <robh+dt@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        devicetree@...r.kernel.org, Damien Le Moal <damien.lemoal@....com>,
        Anup Patel <anup@...infault.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Atish Patra <atish.patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v3 0/4] Dedicated CLINT timer driver

On Wed, 15 Jul 2020 at 09:15, Anup Patel <anup.patel@....com> wrote:
> 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-rc5 and can be found at riscv_clint_v3
> 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 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          |  58 +++++
>  arch/riscv/Kconfig                            |   2 +-
>  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             | 229 ++++++++++++++++++
>  drivers/clocksource/timer-riscv.c             |  17 +-
>  include/linux/cpuhotplug.h                    |   1 +
>  16 files changed, 369 insertions(+), 147 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

If it makes any difference I tested this both in Qemu and on the
HiFive Unleashed,
but I don't have a working no-mmu setup.

Tested-by: Emil Renner Berhing <kernel@...il.dk>

/Emil