[PATCH 3.18 087/185] usb: musb: call pm_runtime_{get,put}_sync before reading vbus registers

[Greg Kroah-Hartman]

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Merlijn Wajer <merlijn@xxxxxxxxxx>

[ Upstream commit df6b074dbe248d8c43a82131e8fd429e401841a5 ]

Without pm_runtime_{get,put}_sync calls in place, reading
vbus status via /sys causes the following error:

Unhandled fault: external abort on non-linefetch (0x1028) at 0xfa0ab060
pgd = b333e822
[fa0ab060] *pgd=48011452(bad)

[<c05261b0>] (musb_default_readb) from [<c0525bd0>] (musb_vbus_show+0x58/0xe4)
[<c0525bd0>] (musb_vbus_show) from [<c04c0148>] (dev_attr_show+0x20/0x44)
[<c04c0148>] (dev_attr_show) from [<c0259f74>] (sysfs_kf_seq_show+0x80/0xdc)
[<c0259f74>] (sysfs_kf_seq_show) from [<c0210bac>] (seq_read+0x250/0x448)
[<c0210bac>] (seq_read) from [<c01edb40>] (__vfs_read+0x1c/0x118)
[<c01edb40>] (__vfs_read) from [<c01edccc>] (vfs_read+0x90/0x144)
[<c01edccc>] (vfs_read) from [<c01ee1d0>] (SyS_read+0x3c/0x74)
[<c01ee1d0>] (SyS_read) from [<c0106fe0>] (ret_fast_syscall+0x0/0x54)

Solution was suggested by Tony Lindgren <tony@xxxxxxxxxxx>.

Signed-off-by: Merlijn Wajer <merlijn@xxxxxxxxxx>
Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
Signed-off-by: Bin Liu <b-liu@xxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/usb/musb/musb_core.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/usb/musb/musb_core.c
+++ b/drivers/usb/musb/musb_core.c
@@ -1700,6 +1700,7 @@ musb_vbus_show(struct device *dev, struc
 	unsigned long	val;
 	int		vbus;
 
+	pm_runtime_get_sync(dev);
 	spin_lock_irqsave(&musb->lock, flags);
 	val = musb->a_wait_bcon;
 	/* FIXME get_vbus_status() is normally #defined as false...
@@ -1707,6 +1708,7 @@ musb_vbus_show(struct device *dev, struc
 	 */
 	vbus = musb_platform_get_vbus_status(musb);
 	spin_unlock_irqrestore(&musb->lock, flags);
+	pm_runtime_put_sync(dev);
 
 	return sprintf(buf, "Vbus %s, timeout %lu msec\n",
 			vbus ? "on" : "off", val);