[RFC PATCH 03/12] xenbus: add freeze/thaw/restore callbacks support

[Anchal Agarwal <anchalag@amazon.com>]

From: Munehisa Kamata <kamatam@amazon.com>

Since commit b3e96c0c7562 ("xen: use freeze/restore/thaw PM events for
suspend/resume/chkpt"), xenbus uses PMSG_FREEZE, PMSG_THAW and
PMSG_RESTORE events for Xen suspend. However, they're actually assigned
to xenbus_dev_suspend(), xenbus_dev_cancel() and xenbus_dev_resume()
respectively, and only suspend and resume callbacks are supported at
driver level. To support PM suspend and PM hibernation, modify the bus
level PM callbacks to invoke not only device driver's suspend/resume but
also freeze/thaw/restore.

Note that we'll use freeze/restore callbacks even for PM suspend whereas
suspend/resume callbacks are normally used in the case, becausae the
existing xenbus device drivers already have suspend/resume callbacks
specifically designed for Xen suspend. So we can allow the device
drivers to keep the existing callbacks wihtout modification.

Signed-off-by: Munehisa Kamata <kamatam@amazon.com>
Signed-off-by: Anchal Agarwal <anchalag@amazon.com>
Reviewed-by: Munehisa Kamata <kamatam@amazon.com>
Reviewed-by: Eduardo Valentin <eduval@amazon.com>
---
 drivers/xen/xenbus/xenbus_probe.c | 102 ++++++++++++++++++++++++++++++++------
 include/xen/xenbus.h              |   3 ++
 2 files changed, 89 insertions(+), 16 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index ec9eb4f..95b0a6d 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -49,6 +49,7 @@
 #include <linux/io.h>
 #include <linux/slab.h>
 #include <linux/module.h>
+#include <linux/suspend.h>
 
 #include <asm/page.h>
 #include <asm/pgtable.h>
@@ -588,26 +589,47 @@ int xenbus_dev_suspend(struct device *dev)
 	struct xenbus_driver *drv;
 	struct xenbus_device *xdev
 		= container_of(dev, struct xenbus_device, dev);
+	int (*cb)(struct xenbus_device *) = NULL;
+	bool xen_suspend = xen_suspend_mode_is_xen_suspend();
 
 	DPRINTK("%s", xdev->nodename);
 
 	if (dev->driver == NULL)
 		return 0;
 	drv = to_xenbus_driver(dev->driver);
-	if (drv->suspend)
-		err = drv->suspend(xdev);
-	if (err)
-		pr_warn("suspend %s failed: %i\n", dev_name(dev), err);
+
+	if (xen_suspend)
+		cb = drv->suspend;
+	else
+		cb = drv->freeze;
+
+	if (cb)
+		err = cb(xdev);
+
+	if (err) {
+		pr_warn("%s %s failed: %i\n", xen_suspend ?
+			"suspend" : "freeze", dev_name(dev), err);
+		return err;
+	}
+
+	if (!xen_suspend) {
+		/* Forget otherend since this can become stale after restore */
+		free_otherend_watch(xdev);
+		free_otherend_details(xdev);
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(xenbus_dev_suspend);
 
 int xenbus_dev_resume(struct device *dev)
 {
-	int err;
+	int err = 0;
 	struct xenbus_driver *drv;
 	struct xenbus_device *xdev
 		= container_of(dev, struct xenbus_device, dev);
+	int (*cb)(struct xenbus_device *) = NULL;
+	bool xen_suspend = xen_suspend_mode_is_xen_suspend();
 
 	DPRINTK("%s", xdev->nodename);
 
@@ -616,24 +638,34 @@ int xenbus_dev_resume(struct device *dev)
 	drv = to_xenbus_driver(dev->driver);
 	err = talk_to_otherend(xdev);
 	if (err) {
-		pr_warn("resume (talk_to_otherend) %s failed: %i\n",
+		pr_warn("%s (talk_to_otherend) %s failed: %i\n",
+			xen_suspend ? "resume" : "restore",
 			dev_name(dev), err);
 		return err;
 	}
 
-	xdev->state = XenbusStateInitialising;
+	if (xen_suspend)
+		xdev->state = XenbusStateInitialising;
 
-	if (drv->resume) {
-		err = drv->resume(xdev);
-		if (err) {
-			pr_warn("resume %s failed: %i\n", dev_name(dev), err);
-			return err;
-		}
+	if (xen_suspend)
+		cb = drv->resume;
+	else
+		cb = drv->restore;
+
+	if (cb)
+		err = cb(xdev);
+
+	if (err) {
+		pr_warn("%s %s failed: %i\n",
+			xen_suspend ? "resume" : "restore",
+			dev_name(dev), err);
+		return err;
 	}
 
 	err = watch_otherend(xdev);
 	if (err) {
-		pr_warn("resume (watch_otherend) %s failed: %d.\n",
+		pr_warn("%s (watch_otherend) %s failed: %d.\n",
+			xen_suspend ? "resume" : "restore",
 			dev_name(dev), err);
 		return err;
 	}
@@ -644,8 +676,46 @@ EXPORT_SYMBOL_GPL(xenbus_dev_resume);
 
 int xenbus_dev_cancel(struct device *dev)
 {
-	/* Do nothing */
-	DPRINTK("cancel");
+	int err = 0;
+	struct xenbus_driver *drv;
+	struct xenbus_device *xdev
+		= container_of(dev, struct xenbus_device, dev);
+	bool xen_suspend = xen_suspend_mode_is_xen_suspend();
+
+	if (xen_suspend) {
+		/* Do nothing */
+		DPRINTK("cancel");
+		return 0;
+	}
+
+	DPRINTK("%s", xdev->nodename);
+
+	if (dev->driver == NULL)
+		return 0;
+	drv = to_xenbus_driver(dev->driver);
+
+	err = talk_to_otherend(xdev);
+	if (err) {
+		pr_warn("thaw (talk_to_otherend) %s failed: %d.\n",
+			dev_name(dev), err);
+		return err;
+	}
+
+	if (drv->thaw) {
+		err = drv->thaw(xdev);
+		if (err) {
+			pr_warn("thaw %s failed: %i\n", dev_name(dev), err);
+			return err;
+		}
+	}
+
+	err = watch_otherend(xdev);
+	if (err) {
+		pr_warn("thaw (watch_otherend) %s failed: %d.\n",
+			dev_name(dev), err);
+		return err;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(xenbus_dev_cancel);
diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index 869c816..20261d5 100644
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -100,6 +100,9 @@ struct xenbus_driver {
 	int (*remove)(struct xenbus_device *dev);
 	int (*suspend)(struct xenbus_device *dev);
 	int (*resume)(struct xenbus_device *dev);
+	int (*freeze)(struct xenbus_device *dev);
+	int (*thaw)(struct xenbus_device *dev);
+	int (*restore)(struct xenbus_device *dev);
 	int (*uevent)(struct xenbus_device *, struct kobj_uevent_env *);
 	struct device_driver driver;
 	int (*read_otherend_details)(struct xenbus_device *dev);
-- 
2.7.4