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

[Ingo Molnar]

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@xxxxxxxxx>

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

Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Maxim Levitsky <maximlevitsky@xxxxxxxxx>

---
 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
-
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