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From:   Anup Patel <anup@brainfault.org>
Date:   Sun, 7 Mar 2021 09:15:49 +0530
Message-ID: <CAAhSdy16JtDj81iXgXTY=n2i-svvR4u8y=1WxmxwZgAPNiH7cQ@mail.gmail.com>
Subject: Re: [PATCH 2/2] riscv: Enable generic clockevent broadcast
To:     Guo Ren <guoren@kernel.org>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>,
        linux-arch@vger.kernel.org, linux-csky@vger.kernel.org,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Guo Ren <guoren@linux.alibaba.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Anup Patel <anup.patel@wdc.com>,
        Atish Patra <atish.patra@wdc.com>,
        Palmer Dabbelt <palmerdabbelt@google.com>,
        Greentime Hu <greentime.hu@sifive.com>
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On Sun, Mar 7, 2021 at 7:55 AM <guoren@kernel.org> wrote:
>
> From: Guo Ren <guoren@linux.alibaba.com>
>
> When percpu-timers are stopped by deep power saving mode, we
> need system timer help to broadcast IPI_TIMER.
>
> This is first introduced by broken x86 hardware, where the local apic
> timer stops in C3 state. But many other architectures(powerpc, mips,
> arm, hexagon, openrisc, sh) have supported the infrastructure to
> deal with Power Management issues.
>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: Anup Patel <anup.patel@wdc.com>
> Cc: Atish Patra <atish.patra@wdc.com>
> Cc: Palmer Dabbelt <palmerdabbelt@google.com>
> Cc: Greentime Hu <greentime.hu@sifive.com>

Looks good to me.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

> ---
>  arch/riscv/Kconfig      |  2 ++
>  arch/riscv/kernel/smp.c | 16 ++++++++++++++++
>  2 files changed, 18 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 85d626b8ce5e..8637e7344abe 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -28,6 +28,7 @@ config RISCV
>         select ARCH_HAS_SET_DIRECT_MAP
>         select ARCH_HAS_SET_MEMORY
>         select ARCH_HAS_STRICT_KERNEL_RWX if MMU
> +       select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>         select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
>         select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
>         select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
> @@ -39,6 +40,7 @@ config RISCV
>         select EDAC_SUPPORT
>         select GENERIC_ARCH_TOPOLOGY if SMP
>         select GENERIC_ATOMIC64 if !64BIT
> +       select GENERIC_CLOCKEVENTS_BROADCAST if SMP
>         select GENERIC_EARLY_IOREMAP
>         select GENERIC_GETTIMEOFDAY if HAVE_GENERIC_VDSO
>         select GENERIC_IOREMAP
> diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
> index ea028d9e0d24..8325d33411d8 100644
> --- a/arch/riscv/kernel/smp.c
> +++ b/arch/riscv/kernel/smp.c
> @@ -9,6 +9,7 @@
>   */
>
>  #include <linux/cpu.h>
> +#include <linux/clockchips.h>
>  #include <linux/interrupt.h>
>  #include <linux/module.h>
>  #include <linux/profile.h>
> @@ -27,6 +28,7 @@ enum ipi_message_type {
>         IPI_CALL_FUNC,
>         IPI_CPU_STOP,
>         IPI_IRQ_WORK,
> +       IPI_TIMER,
>         IPI_MAX
>  };
>
> @@ -176,6 +178,12 @@ void handle_IPI(struct pt_regs *regs)
>                         irq_work_run();
>                 }
>
> +#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
> +               if (ops & (1 << IPI_TIMER)) {
> +                       stats[IPI_TIMER]++;
> +                       tick_receive_broadcast();
> +               }
> +#endif
>                 BUG_ON((ops >> IPI_MAX) != 0);
>
>                 /* Order data access and bit testing. */
> @@ -192,6 +200,7 @@ static const char * const ipi_names[] = {
>         [IPI_CALL_FUNC]         = "Function call interrupts",
>         [IPI_CPU_STOP]          = "CPU stop interrupts",
>         [IPI_IRQ_WORK]          = "IRQ work interrupts",
> +       [IPI_TIMER]             = "Timer broadcast interrupts",
>  };
>
>  void show_ipi_stats(struct seq_file *p, int prec)
> @@ -217,6 +226,13 @@ void arch_send_call_function_single_ipi(int cpu)
>         send_ipi_single(cpu, IPI_CALL_FUNC);
>  }
>
> +#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
> +void tick_broadcast(const struct cpumask *mask)
> +{
> +       send_ipi_mask(mask, IPI_TIMER);
> +}
> +#endif
> +
>  void smp_send_stop(void)
>  {
>         unsigned long timeout;
> --
> 2.25.1
>
>
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