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Subject回复:[PATCH] cpuidle: add riscv cpuidle driver
Hi Palmer,

> > 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@allwinnertech.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?

Thank you for your suggestions.
I am considering following Anup's suggestion - delete cpuidle.c and implement
cpu_do_idle in cpuidle.h.

> > 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.

Thanks, i'll modify it

> 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?

Based on your comments, I run a test and found that arch_cpu_idle could be executed
normally without enabling the idle driver.Part of the code of the experiment:

+static inline void cpu_do_idle(void)
+{
+ mb();
+ wait_for_interrupt();
+}

void arch_cpu_idle(void)
{
- wait_for_interrupt();
+ cpu_do_idle();
local_irq_enable();
}

> > +}
> > 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.

yes, i'll modify it

> > + 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.

Although, the driver in this case is not necessary, it is essential when work
in the macro CPU_PM_CPU_IDLE_ENTER_PARAM.And it could also be used for supporting
other deeper states in the future. So I think it would be better to keep
riscv_low_level_suspend_enter but change it to __weak function.

> > +}
> > +
> > +/* 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);

Regards,
liush
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