linux-kernel - Re: [PATCH v2 0/5] Dedicated CLINT timer driver

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Message-ID: <CAAhSdy3mHhaKTrhRnNd_gGv7GbmjqxkB28sOw4q7ZTxw4oRd1Q@mail.gmail.com>
Date:   Tue, 14 Jul 2020 09:19:57 +0530
From:   Anup Patel <anup@...infault.org>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     Anup Patel <Anup.Patel@....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>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Atish Patra <Atish.Patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 0/5] Dedicated CLINT timer driver

On Tue, Jul 14, 2020 at 4:32 AM Palmer Dabbelt <palmer@...belt.com> wrote:
>
> On Sat, 27 Jun 2020 09:19:52 PDT (-0700), Anup Patel 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-rc2 and can be found at riscv_clint_v2
> > 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 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 (5):
> >   RISC-V: Add mechanism to provide custom IPI operations
> >   RISC-V: Remove CLINT related code
> >   clocksource/drivers/timer-riscv: Remove MMIO related stuff
> >   clocksource/drivers: Add CLINT timer driver
> >   dt-bindings: timer: Add CLINT bindings
>
> This all generally LGTM, though I haven't been through the code line-by-line
> yet.  It touches a bunch of trees, so I'd prefer to have some Acks before
> merging -- I'll dig through the RISC-V specific stuff, but the new CLINT driver
> probhably deserves a look from one of the clocksource folks.
>
> I think the only issue is that the port will be broken between patch 2 and 4,
> as at that point we won't have an M-mode timer driver.  I think it shouldn't be
> too much to just reorder these, LMK if you want to do it or you want me to.

Okay, I will try your suggestion to reorder patches. There is another minor
build issue reported by test bots which I will fix as well.

I will send v3 in a couple of days before end-of-week.

Regards,
Anup

>
> Thanks!
>
> >
> >  .../bindings/timer/sifive,clint.txt           |  34 +++
> >  arch/riscv/Kconfig                            |   2 +-
> >  arch/riscv/include/asm/clint.h                |  39 ---
> >  arch/riscv/include/asm/smp.h                  |  11 +
> >  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, 337 insertions(+), 147 deletions(-)
> >  create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.txt
> >  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