linux-kernel - Re: [ PATCH] Add suspend/resume for HPET was: Re: [3/6] 2.6.21-rc4: known regressions

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Message-Id: <200703290747.28929.maximlevitsky@gmail.com>
Date:	Thu, 29 Mar 2007 07:47:28 +0200
From:	Maxim <maximlevitsky@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Jeff Chua <jeff.chua.linux@...il.com>,
	Adrian Bunk <bunk@...sta.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, pavel@...e.cz,
	linux-pm@...ts.osdl.org, gregkh@...e.de,
	linux-pci@...ey.karlin.mff.cuni.cz,
	Jens Axboe <jens.axboe@...cle.com>,
	Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
	jgarzik@...ox.com, linux-ide@...r.kernel.org,
	"Michael S. Tsirkin" <mst@...lanox.co.il>
Subject: Re: [ PATCH] Add suspend/resume for HPET was: Re: [3/6] 2.6.21-rc4: known regressions

On Thursday 29 March 2007 07:08:58 Linus Torvalds wrote:
> 
> On Thu, 29 Mar 2007, Maxim wrote:
> >
> > 	I am sending here a patch that as was discussed here adds hpet to list of system devices
> > 	and adds suspend/resume hooks this way.
> > 	I tested it and it works fine.
> 
> Ok, it certainly looks better, but it *also* looks like it just assumes 
> the HPET is there. Which would work in testing _with_ a HPET, but would 
> likely break on hardware without one, no?
> 
> Shouldn't there be at least something like a
> 
> 	if (!is_hpet_capable())
> 		return 0;
> 
> at the top of that init routine? I'd also expect that you'd need to check 
> that "hpet_virt_address" is valid or something?
> 
> (Or, better yet, shouldn't we set "boot_hpet_disable" when we decide not 
> to use the HPET, and set hpet_virt_address to NULL?)

This is done here

out_nohpet:
	iounmap(hpet_virt_address);
	hpet_virt_address = NULL;
> 
> 		Linus
> 

Hi, 
	Of course, I forgot.

	I was planning to put sysdev code in hpet_enable()
	but it is not possible because this function is called too early.

	Thus I put sysdev initialization  in separate function but forgot to test for HPET

	Thanks a lot.

	Best regards
		Maxim Levitsky

---
This adds support of suspend/resume on i386 for HPET
Signed-off-by: Maxim Levitsky <maximlevitsky@...il.com>

---
 arch/i386/kernel/hpet.c |   68 +++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 68 insertions(+), 0 deletions(-)

diff --git a/arch/i386/kernel/hpet.c b/arch/i386/kernel/hpet.c
index 0fd9fba..7c67780 100644
--- a/arch/i386/kernel/hpet.c
+++ b/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>
@@ -310,6 +312,7 @@ int __init hpet_enable(void)
 out_nohpet:
 	iounmap(hpet_virt_address);
 	hpet_virt_address = NULL;
+	boot_hpet_disable = 1;
 	return 0;
 }
 
@@ -524,3 +527,68 @@ irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id)
 	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) {
+		sysdev_register(&hpet_device);
+		if (err)
+			sysdev_class_unregister(&hpet_class);
+	}
+
+	return err;
+}
+
+device_initcall(hpet_register_sysfs);
+
+#endif
-- 
1.4.4.2

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