linux-kernel - Re: [PATCH 2/2] riscv: Enable generic clockevent broadcast

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Message-ID: <mhng-25b45eaf-1d0b-4292-9228-1ac3ac68832b@palmerdabbelt-glaptop>
Date:   Tue, 16 Mar 2021 20:40:38 -0700 (PDT)
From:   Palmer Dabbelt <palmerdabbelt@...gle.com>
To:     guoren@...nel.org
CC:     Arnd Bergmann <arnd@...db.de>, guoren@...nel.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-csky@...r.kernel.org, linux-riscv@...ts.infradead.org,
        guoren@...ux.alibaba.com, tglx@...utronix.de,
        daniel.lezcano@...aro.org, Anup Patel <Anup.Patel@....com>,
        Atish Patra <Atish.Patra@....com>, greentime.hu@...ive.com
Subject:     Re: [PATCH 2/2] riscv: Enable generic clockevent broadcast

On Sat, 06 Mar 2021 18:24:46 PST (-0800), guoren@...nel.org wrote:
> From: Guo Ren <guoren@...ux.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@...ux.alibaba.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Cc: Anup Patel <anup.patel@....com>
> Cc: Atish Patra <atish.patra@....com>
> Cc: Palmer Dabbelt <palmerdabbelt@...gle.com>
> Cc: Greentime Hu <greentime.hu@...ive.com>
> ---
>  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;

Thanks, this is on for-next.