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Date: Tue, 26 May 2015 10:19:57 +0800
From: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
xinhuix.pan@...el.com,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Alan Cox <alan@...ux.intel.com>
Subject: [PATCH 1/3] usb: add function usb_autopm_get_interface_upgrade
Some usb driver has a specific requirement. Their critical functions
might be called under both atomic environment and non-atomic environment.
If it's under atomic environment, the driver can wake up the device
by calling pm_runtime_get_sync directly.
If it's under non-atomic environment, the function's caller need wake
up the device before the function accesses the device.
The patch adds usb_autopm_get_interface_upgrade, a new function to
support above capability.
Signed-off-by: Zhang Yanmin <yanmin.zhang@...el.com>
---
drivers/usb/core/driver.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/usb.h | 3 +++
2 files changed, 56 insertions(+)
diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 818369a..d07fd8d 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1684,6 +1684,59 @@ int usb_autopm_get_interface(struct usb_interface *intf)
EXPORT_SYMBOL_GPL(usb_autopm_get_interface);
/**
+ * usb_autopm_get_interface_retry - increment a USB interface's PM-usage counter
+ * @intf: the usb_interface whose counter should be incremented
+ *
+ * This routine should be called by an interface driver when it wants to
+ * use @intf and needs to guarantee that it is not suspended. In addition,
+ * the routine prevents @intf from being autosuspended subsequently. (Note
+ * that this will not prevent suspend events originating in the PM core.)
+ * This prevention will persist until usb_autopm_put_interface() is called
+ * or @intf is unbound. A typical example would be a character-device
+ * driver when its device file is opened.
+ *
+ * Comparing with usb_autopm_get_interface, usb_autopm_get_interface_upgrade
+ * is more careful when resuming the device.
+ * 1) The caller's caller already resumes resume the device and hold spinlocks.
+ * usb_autopm_get_interface_upgrade couldn't call pm_runtime_get_sync;
+ * 2) The caller's caller doesn't resume the device.
+ * usb_autopm_get_interface_upgrade has to resume the device before going ahead.
+ *
+ * @intf's usage counter is incremented to prevent subsequent autosuspends.
+ * However if the autoresume fails then the counter is re-decremented.
+ *
+ * This routine can run only in process context.
+ *
+ * Return: 0 on success.
+ */
+int usb_autopm_get_interface_upgrade(struct usb_interface *intf)
+{
+ int status = 0;
+
+ pm_runtime_get(&intf->dev);
+ if (!pm_runtime_active(&intf->dev)) {
+ /* If not active, next _get_sync wakes device up*/
+ status = pm_runtime_get_sync(&intf->dev);
+ /*
+ * If it's active, next _put_sync wouldn't
+ * really put it to sleep as the 1st _get
+ * keeps the device active.
+ */
+ pm_runtime_put_sync(&intf->dev);
+ if (status < 0)
+ pm_runtime_put(&intf->dev);
+ } else
+ atomic_inc(&intf->pm_usage_cnt);
+ dev_vdbg(&intf->dev, "%s: cnt %d -> %d\n",
+ __func__, atomic_read(&intf->dev.power.usage_count),
+ status);
+ if (status > 0)
+ status = 0;
+ return status;
+}
+EXPORT_SYMBOL_GPL(usb_autopm_get_interface_upgrade);
+
+/**
* usb_autopm_get_interface_async - increment a USB interface's PM-usage counter
* @intf: the usb_interface whose counter should be incremented
*
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 447fe29..0a8a44a 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -663,6 +663,7 @@ extern void usb_enable_autosuspend(struct usb_device *udev);
extern void usb_disable_autosuspend(struct usb_device *udev);
extern int usb_autopm_get_interface(struct usb_interface *intf);
+extern int usb_autopm_get_interface_upgrade(struct usb_interface *intf);
extern void usb_autopm_put_interface(struct usb_interface *intf);
extern int usb_autopm_get_interface_async(struct usb_interface *intf);
extern void usb_autopm_put_interface_async(struct usb_interface *intf);
@@ -683,6 +684,8 @@ static inline int usb_disable_autosuspend(struct usb_device *udev)
static inline int usb_autopm_get_interface(struct usb_interface *intf)
{ return 0; }
+static inline int usb_autopm_get_interface_upgrade(struct usb_interface *intf)
+{ return 0; }
static inline int usb_autopm_get_interface_async(struct usb_interface *intf)
{ return 0; }
--
1.9.1
--
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