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Message-ID: <mhng-e743b908-36de-4226-832d-bc5acbbfd81b@palmerdabbelt-glaptop1>
Date: Mon, 14 Sep 2020 15:08:35 -0700 (PDT)
From: Palmer Dabbelt <palmer@...belt.com>
To: liush@...winnertech.com
CC: Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
rjw@...ysocki.net, daniel.lezcano@...aro.org,
Anup Patel <Anup.Patel@....com>,
Atish Patra <Atish.Patra@....com>,
Damien Le Moal <Damien.LeMoal@....com>,
wangkefeng.wang@...wei.com, kernel@...il.dk, zong.li@...ive.com,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org, liush@...winnertech.com
Subject: Re: [PATCH] cpuidle: add riscv cpuidle driver
On Sun, 13 Sep 2020 18:52:03 PDT (-0700), liush@...winnertech.com wrote:
> This patch adds a cpuidle driver for systems based RISCV architecture.
> This patch supports state WFI. Other states will be supported in the
> future.
>
> Signed-off-by: liush <liush@...winnertech.com>
> ---
> arch/riscv/Kconfig | 7 +++++
> arch/riscv/include/asm/cpuidle.h | 7 +++++
> arch/riscv/kernel/Makefile | 1 +
> arch/riscv/kernel/cpuidle.c | 8 ++++++
> drivers/cpuidle/Kconfig | 5 ++++
> drivers/cpuidle/Kconfig.riscv | 11 ++++++++
> drivers/cpuidle/Makefile | 4 +++
> drivers/cpuidle/cpuidle-riscv.c | 55 ++++++++++++++++++++++++++++++++++++++++
> 8 files changed, 98 insertions(+)
> create mode 100644 arch/riscv/include/asm/cpuidle.h
> create mode 100644 arch/riscv/kernel/cpuidle.c
> create mode 100644 drivers/cpuidle/Kconfig.riscv
> create mode 100644 drivers/cpuidle/cpuidle-riscv.c
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index df18372..c7ddb9d 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -86,6 +86,7 @@ config RISCV
> select SPARSE_IRQ
> select SYSCTL_EXCEPTION_TRACE
> select THREAD_INFO_IN_TASK
> + select CPU_IDLE
>
> config ARCH_MMAP_RND_BITS_MIN
> default 18 if 64BIT
> @@ -407,6 +408,12 @@ config BUILTIN_DTB
> depends on RISCV_M_MODE
> depends on OF
>
> +menu "CPU Power Management"
> +
> +source "drivers/cpuidle/Kconfig"
> +
> +endmenu
> +
> menu "Power management options"
>
> source "kernel/power/Kconfig"
> diff --git a/arch/riscv/include/asm/cpuidle.h b/arch/riscv/include/asm/cpuidle.h
> new file mode 100644
> index 00000000..2599d2f
> --- /dev/null
> +++ b/arch/riscv/include/asm/cpuidle.h
> @@ -0,0 +1,7 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __RISCV_CPUIDLE_H
> +#define __RISCV_CPUIDLE_H
> +
> +extern void cpu_do_idle(void);
> +
> +#endif
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index dc93710..396ba9c 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -29,6 +29,7 @@ obj-y += riscv_ksyms.o
> obj-y += stacktrace.o
> obj-y += cacheinfo.o
> obj-y += patch.o
> +obj-y += cpuidle.o
Presumably we want this to be a Kconfig option, if only to avoid excess size on
the smaller systems?
> obj-$(CONFIG_MMU) += vdso.o vdso/
>
> obj-$(CONFIG_RISCV_M_MODE) += traps_misaligned.o
> diff --git a/arch/riscv/kernel/cpuidle.c b/arch/riscv/kernel/cpuidle.c
> new file mode 100644
> index 00000000..a3289e7
> --- /dev/null
> +++ b/arch/riscv/kernel/cpuidle.c
> @@ -0,0 +1,8 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <asm/cpuidle.h>
> +
> +void cpu_do_idle(void)
> +{
> + __asm__ __volatile__ ("wfi");
> +
We have wait_for_interrupt() that does this already, but it's one line so it
doesn't really matter. Either way, there's an extra newline here.
Additionally, we have arch_cpu_idle() which is calling cpu_do_idle() on other
platforms. Presumably we should be doing something similar, under the
assumption that we will eventually have cpu_do_idle() hook into CPU idle
drivers here?
> +}
> diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
> index c0aeedd..f6be0fd 100644
> --- a/drivers/cpuidle/Kconfig
> +++ b/drivers/cpuidle/Kconfig
> @@ -62,6 +62,11 @@ depends on PPC
> source "drivers/cpuidle/Kconfig.powerpc"
> endmenu
>
> +menu "RISCV CPU Idle Drivers"
> +depends on RISCV
> +source "drivers/cpuidle/Kconfig.riscv"
> +endmenu
> +
> config HALTPOLL_CPUIDLE
> tristate "Halt poll cpuidle driver"
> depends on X86 && KVM_GUEST
> diff --git a/drivers/cpuidle/Kconfig.riscv b/drivers/cpuidle/Kconfig.riscv
> new file mode 100644
> index 00000000..e86d36b
> --- /dev/null
> +++ b/drivers/cpuidle/Kconfig.riscv
> @@ -0,0 +1,11 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +#
> +# RISCV CPU Idle drivers
> +#
> +config RISCV_CPUIDLE
> + bool "Generic RISCV CPU idle Driver"
> + select DT_IDLE_STATES
> + select CPU_IDLE_MULTIPLE_DRIVERS
Looks like there's some space/tab issues here. IIRC checkpatch will catch this
sort of thing.
> + help
> + Select this option to enable generic cpuidle driver for RISCV.
> + Now only support C0 State.
> diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile
> index 26bbc5e..4c83c4e 100644
> --- a/drivers/cpuidle/Makefile
> +++ b/drivers/cpuidle/Makefile
> @@ -34,3 +34,7 @@ obj-$(CONFIG_MIPS_CPS_CPUIDLE) += cpuidle-cps.o
> # POWERPC drivers
> obj-$(CONFIG_PSERIES_CPUIDLE) += cpuidle-pseries.o
> obj-$(CONFIG_POWERNV_CPUIDLE) += cpuidle-powernv.o
> +
> +###############################################################################
> +# RISCV drivers
> +obj-$(CONFIG_RISCV_CPUIDLE) += cpuidle-riscv.o
> diff --git a/drivers/cpuidle/cpuidle-riscv.c b/drivers/cpuidle/cpuidle-riscv.c
> new file mode 100644
> index 00000000..5dddcfa
> --- /dev/null
> +++ b/drivers/cpuidle/cpuidle-riscv.c
> @@ -0,0 +1,55 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * RISC-V CPU idle driver.
> + *
> + * Copyright (C) 2020-2022 Allwinner Ltd
> + *
> + * Based on code - driver/cpuidle/cpuidle-at91.c
> + *
> + */
> +#include <linux/cpuidle.h>
> +#include <linux/cpumask.h>
> +#include <linux/cpu_pm.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/slab.h>
> +#include <linux/platform_device.h>
> +#include <asm/cpuidle.h>
> +
> +#define MAX_IDLE_STATES 1
> +
> +/* TODO: Implement deeper idle states */
> +static int riscv_low_level_suspend_enter(int state)
> +{
> + return 0;
As far as I can tell, this driver just doesn't do anything? Assuming that's
the case, it's probably best to just drop everything but cpu_do_idle() until we
have something to exercise this.
> +}
> +
> +/* Actual code that puts the SoC in different idle states */
> +static int riscv_enter_idle(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv,
> + int index)
> +{
> + return CPU_PM_CPU_IDLE_ENTER_PARAM(riscv_low_level_suspend_enter,
> + index, 0);
> +}
> +
> +static struct cpuidle_driver riscv_idle_driver = {
> + .name = "riscv_idle",
> + .owner = THIS_MODULE,
> + .states[0] = {
> + .enter = riscv_enter_idle,
> + .exit_latency = 1,
> + .target_residency = 1,
> + .name = "WFI",
> + .desc = "RISCV WFI",
> + },
> + .state_count = MAX_IDLE_STATES,
> +};
> +
> +static int __init riscv_cpuidle_init(void)
> +{
> + return cpuidle_register(&riscv_idle_driver, NULL);
> +}
> +
> +device_initcall(riscv_cpuidle_init);
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