Messages in this thread | | | Subject | Re: [PATCH] cpuidle: JZ4780: Add Ingenic JZ4780 cpuidle driver. | From | Zhou Yanjie <> | Date | Sat, 24 Jul 2021 21:36:11 +0800 |
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Hi Paul,
On 2021/7/24 下午7:16, Paul Cercueil wrote: > Hi Zhou, > > Le sam., juil. 24 2021 at 17:19:59 +0800, 周琰杰 (Zhou Yanjie) > <zhouyanjie@wanyeetech.com> a écrit : >> The JZ4780 has a high overhead to executing a MIPS wait on SMP, as a >> core must flush out dirty cache lines from its data cache before doing >> so. This is because the core clock is gated during a wait and if the >> other core tries to access a dirty line from the waiting core's cache, >> it will lock up. >> >> To mitigate some of this impact, this driver provides a simple polling >> top level idle state, to try to avoid the cache flushing overhead when >> the wait will only be short. The second level state is implemented with >> the MIPS wait instruction. >> >> This patch first found in the github repository of CI20, the original >> author is Alex Smith. Because there is a chance to cause kernel hang >> scenarios which can occur within hours or even within days, so this >> patch was abandoned, but now it is determined that this is not the >> problem caused by this patch, but caused by the cache driver. With >> the new Ingenic specific cache driver, it has been working properly >> on CI20 v1 for more than one week. >> >> Tested-by: H. Nikolaus Schaller <hns@goldelico.com> >> Signed-off-by: Alex Smith <alex.smith@imgtec.com> >> Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com> >> --- >> drivers/cpuidle/Kconfig.mips | 8 +++++ >> drivers/cpuidle/Makefile | 1 + >> drivers/cpuidle/cpuidle-jz4780.c | 74 >> ++++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 83 insertions(+) >> create mode 100644 drivers/cpuidle/cpuidle-jz4780.c >> >> diff --git a/drivers/cpuidle/Kconfig.mips b/drivers/cpuidle/Kconfig.mips >> index c3c011a..4a55d24 100644 >> --- a/drivers/cpuidle/Kconfig.mips >> +++ b/drivers/cpuidle/Kconfig.mips >> @@ -16,3 +16,11 @@ config MIPS_CPS_CPUIDLE >> Processing System (CPS) architecture. In order to make use of >> the deepest idle states you will need to ensure that you are >> also using the CONFIG_MIPS_CPS SMP implementation. >> + >> +config MIPS_JZ4780_CPUIDLE >> + bool "CPU Idle driver for Ingenic JZ4780" >> + depends on MACH_JZ4780 && SMP >> + default y >> + help >> + Select this option to enable CPU idle state management through >> + cpuidle for Ingenic JZ4780 platforms. >> diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile >> index 26bbc5e..1dd372f 100644 >> --- a/drivers/cpuidle/Makefile >> +++ b/drivers/cpuidle/Makefile >> @@ -29,6 +29,7 @@ obj-$(CONFIG_ARM_QCOM_SPM_CPUIDLE) += >> cpuidle-qcom-spm.o >> >> ############################################################################### >> >> # MIPS drivers >> obj-$(CONFIG_MIPS_CPS_CPUIDLE) += cpuidle-cps.o >> +obj-$(CONFIG_MIPS_JZ4780_CPUIDLE) += cpuidle-jz4780.o >> >> >> ############################################################################### >> >> # POWERPC drivers >> diff --git a/drivers/cpuidle/cpuidle-jz4780.c >> b/drivers/cpuidle/cpuidle-jz4780.c >> new file mode 100644 >> index 00000000..2025de4 >> --- /dev/null >> +++ b/drivers/cpuidle/cpuidle-jz4780.c >> @@ -0,0 +1,74 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* >> + * JZ4780 CPU idle driver >> + * Copyright (C) 2015 Imagination Technologies >> + * Author: Alex Smith <alex.smith@imgtec.com> >> + * Copyright (c) 2020 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com> >> + */ >> + >> +#include <linux/cpuidle.h> >> +#include <linux/init.h> >> +#include <linux/sched.h> >> +#include <linux/sched/idle.h> >> + >> +#include <asm/idle.h> >> +#include <asm/mipsregs.h> >> + >> +/* >> + * The JZ4780 has a high overhead to entering just the basic MIPS >> wait on SMP, >> + * due to the requirement to flush out dirty lines from the dcache >> before >> + * waiting. Therefore, we try to mitigate this overhead by using a >> simple >> + * polling loop for short waits. >> + */ >> +static int jz4780_cpuidle_poll_enter(struct cpuidle_device *dev, >> + struct cpuidle_driver *drv, int index) >> +{ >> + if (!current_set_polling_and_test()) >> + while (!need_resched() && !(read_c0_cause() & >> read_c0_status() & CAUSEF_IP)) >> + cpu_relax(); >> + >> + current_clr_polling(); >> + local_irq_enable(); >> + >> + return index; >> +} >> + >> +static struct cpuidle_driver jz4780_cpuidle_driver = { >> + .name = "jz4780_cpuidle", >> + .owner = THIS_MODULE, >> + .states = { >> + { >> + .enter = jz4780_cpuidle_poll_enter, >> + .exit_latency = 1, >> + .target_residency = 1, >> + .power_usage = UINT_MAX, >> + .name = "poll", >> + .desc = "polling loop", >> + }, >> + { >> + .enter = mips_cpuidle_wait_enter, >> + .exit_latency = 50, >> + .target_residency = 300, >> + .power_usage = UINT_MAX, >> + .name = "wait", >> + .desc = "MIPS wait", >> + }, >> + }, >> + .state_count = 2, >> +}; >> + >> +static int __init jz4780_cpuidle_init(void) >> +{ >> + int ret; >> + >> + ret = cpuidle_register(&jz4780_cpuidle_driver, NULL); > > You're missing something here - you never check that the kernel is > actually running on a JZ4780.
Sure, I will try to fix it.
Thanks and best regards!
> > Cheers, > -Paul > >> + if (ret) { >> + pr_err("Failed to register JZ4780 idle driver: %d\n", ret); >> + return ret; >> + } >> + >> + pr_info("JZ4780 idle driver registered\n"); >> + >> + return 0; >> +} >> +device_initcall(jz4780_cpuidle_init); >> -- >> 2.7.4 >> >
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