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Patch "phy: twl4030-usb: make runtime pm more reliable." has been added to the 4.1-stable tree

PATCH [email protected] 1 participant 1 message Aug 10, 2015

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This is a note to let you know that I've just added the patch titled

phy: twl4030-usb: make runtime pm more reliable.

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
phy-twl4030-usb-make-runtime-pm-more-reliable.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 56301df6bcaaed31e77b8c500ca1b437f46a3158 Mon Sep 17 00:00:00 2001

From: NeilBrown <[email protected]>
Date: Thu, 16 Apr 2015 18:03:04 +1000
Subject: phy: twl4030-usb: make runtime pm more reliable.

From: NeilBrown <[email protected]>

commit 56301df6bcaaed31e77b8c500ca1b437f46a3158 upstream.

A construct like:

        if (pm_runtime_suspended(twl->dev))
               pm_runtime_get_sync(twl->dev);

is against the spirit of the runtime_pm interface as it makes the internal refcounting useless.

In this case it is also racy, particularly as 'put_autosuspend' is used to drop a reference.
When that happens a timer is started and the device is runtime-suspended after the timeout.
If the above code runs in this window, the device will not be found to be suspended so no pm_runtime reference is taken. When the timer expires the device will be suspended, which is against the intention of the code.

So be more direct is taking and dropping references. If twl->linkstat is VBUS_VALID or ID_GROUND, then hold a pm_runtime reference, otherwise don't.
Define "cable_present()" to test for this condition.

Tested-by Tony Lindgren <[email protected]>
Signed-off-by NeilBrown <[email protected]>
Signed-off-by Kishon Vijay Abraham I <[email protected]>
Cc Alexander Holler <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/phy/phy-twl4030-usb.c |   29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)
drivers/phy/phy-twl4030-usb.c +20 -9
@@ -144,6 +144,16 @@
 #define PMBR1				0x0D
 #define GPIO_USB_4PIN_ULPI_2430C	(3 << 0)
 
+/*
+ * If VBUS is valid or ID is ground, then we know a
+ * cable is present and we need to be runtime-enabled
+ */
+static inline bool cable_present(enum omap_musb_vbus_id_status stat)
+{
+	return stat == OMAP_MUSB_VBUS_VALID ||
+		stat == OMAP_MUSB_ID_GROUND;
+}
+
 struct twl4030_usb {
 	struct usb_phy		phy;
 	struct device		*dev;

@@ -536,8 +546,10 @@ static irqreturn_t twl4030_usb_irq(int i
 
 	mutex_lock(&twl->lock);
 	if (status >= 0 && status != twl->linkstat) {
+		status_changed =
+			cable_present(twl->linkstat) !=
+			cable_present(status);
 		twl->linkstat = status;
-		status_changed = true;
 	}
 	mutex_unlock(&twl->lock);
 

@@ -553,15 +565,11 @@ static irqreturn_t twl4030_usb_irq(int i
 		 * USB_LINK_VBUS state.  musb_hdrc won't care until it
 		 * starts to handle softconnect right.
 		 */
-		if ((status == OMAP_MUSB_VBUS_VALID) ||
-		    (status == OMAP_MUSB_ID_GROUND)) {
-			if (pm_runtime_suspended(twl->dev))
-				pm_runtime_get_sync(twl->dev);
+		if (cable_present(status)) {
+			pm_runtime_get_sync(twl->dev);
 		} else {
-			if (pm_runtime_active(twl->dev)) {
-				pm_runtime_mark_last_busy(twl->dev);
-				pm_runtime_put_autosuspend(twl->dev);
-			}
+			pm_runtime_mark_last_busy(twl->dev);
+			pm_runtime_put_autosuspend(twl->dev);
 		}
 		omap_musb_mailbox(status);
 	}

@@ -766,6 +774,9 @@ static int twl4030_usb_remove(struct pla
 
 	/* disable complete OTG block */
 	twl4030_usb_clear_bits(twl, POWER_CTRL, POWER_CTRL_OTG_ENAB);
+
+	if (cable_present(twl->linkstat))
+		pm_runtime_put_noidle(twl->dev);
 	pm_runtime_mark_last_busy(twl->dev);
 	pm_runtime_put(twl->dev);

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/phy-twl4030-usb-make-runtime-pm-more-reliable.patch