Re: [patch, v2] add suspend/resume for HPET

Ingo Molnar
2007-03-29T17:49:32Z

update: i've tested Maxim's v2 patch on both a hpet-capable and a
hpet-less system, and it works fine here.

on a dual-core hpet-capable system, running a NO_HZ+!HIGH_RES_TIMERS
kernel:

europe:~> grep Clock /proc/timer_list
Clock Event Device: hpet
Clock Event Device: lapic
Clock Event Device: lapic

s2ram works fine now - it hung on resume before.

on a dual-core non-hpet system, with a NO_HZ+!HIGH_RES_TIMERS kernel:

neptune:~> grep Clock /proc/timer_list
Clock Event Device: pit
Clock Event Device: lapic
Clock Event Device: lapic

s2ram worked fine before - and it still works now.

(The combination of NO_HZ+!HIGH_RES_TIMERS was the most fragile wrt.
suspend because in the !HIGH_RES_TIMERS there's just a single instance
after resume that we touch the timer hardware, and we very much rely on
the periodic interrupt being set to the precise value.)

So this is a go on my systems - good work Maxim! (I've reproduced
Maxim's patch below with minor patch-metadata updates.)

Ingo

---------------------------->
Subject: [patch] add suspend/resume for HPET
From: Maxim Levitsky <maximlevitsky@gmail.com>

This adds support for suspend/resume on i386 for HPET.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>

---
arch/i386/kernel/hpet.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 68 insertions(+)

Index: linux/arch/i386/kernel/hpet.c
===================================================================
--- linux.orig/arch/i386/kernel/hpet.c
+++ linux/arch/i386/kernel/hpet.c
@@ -3,6 +3,8 @@
#include <linux/errno.h>
#include <linux/hpet.h>
#include <linux/init.h>
+#include <linux/sysdev.h>
+#include <linux/pm.h>

#include <asm/hpet.h>
#include <asm/io.h>
@@ -307,6 +309,7 @@ int __init hpet_enable(void)
out_nohpet:
iounmap(hpet_virt_address);
hpet_virt_address = NULL;
+ boot_hpet_disable = 1;
return 0;
}

@@ -523,3 +526,68 @@ irqreturn_t hpet_rtc_interrupt(int irq,
return IRQ_HANDLED;
}
#endif
+
+
+/*
+ * Suspend/resume part
+ */
+
+#ifdef CONFIG_PM
+
+static int hpet_suspend(struct sys_device *sys_device, pm_message_t state)
+{
+ unsigned long cfg = hpet_readl(HPET_CFG);
+
+ cfg &= ~(HPET_CFG_ENABLE|HPET_CFG_LEGACY);
+ hpet_writel(cfg, HPET_CFG);
+
+ return 0;
+}
+
+static int hpet_resume(struct sys_device *sys_device)
+{
+ unsigned int id;
+
+ hpet_start_counter();
+
+ id = hpet_readl(HPET_ID);
+
+ if (id & HPET_ID_LEGSUP)
+ hpet_enable_int();
+
+ return 0;
+}
+
+static struct sysdev_class hpet_class = {
+ set_kset_name("hpet"),
+ .suspend = hpet_suspend,
+ .resume = hpet_resume,
+};
+
+static struct sys_device hpet_device = {
+ .id = 0,
+ .cls = &hpet_class,
+};
+
+
+static __init int hpet_register_sysfs(void)
+{
+ int err;
+
+ if (!is_hpet_capable())
+ return 0;
+
+ err = sysdev_class_register(&hpet_class);
+
+ if (!err) {
+ err = sysdev_register(&hpet_device);
+ if (err)
+ sysdev_class_unregister(&hpet_class);
+ }
+
+ return err;
+}
+
+device_initcall(hpet_register_sysfs);
+
+#endif