USB: twl4030-usb: fix minor reporting goofage

Fix a reporting glitch in the twl4030 USB transceiver code.
It wasn't properly distinguishing the two types of active
USB link:  ID grounded, vs not.  In the current code that
distinction doesn't much matter; in the future this bugfix
should help support better USB controller communications.

Provide a comment sorting out some of the cryptic bits of
the manual:  different sections use different names for
key signals, and the register definitions don't help much
without the explanations and diagrams.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 19 insertions, 7 deletions

diff --git a/drivers/usb/otg/twl4030-usb.c b/drivers/usb/otg/twl4030-usb.c
index c34e63910acb..9e3e7a5c258b 100644
--- a/drivers/usb/otg/twl4030-usb.c
+++ b/drivers/usb/otg/twl4030-usb.c
@@ -217,6 +217,7 @@
 
 /* In module TWL4030_MODULE_PM_MASTER */
 #define PROTECT_KEY                     0x0E
+#define STS_HW_CONDITIONS               0x0F
 
 /* In module TWL4030_MODULE_PM_RECEIVER */
 #define VUSB_DEDICATED1                 0x7D
@@ -351,15 +352,26 @@ static enum linkstat twl4030_usb_linkstat(struct twl4030_usb *twl)
         int     status;
         int     linkstat = USB_LINK_UNKNOWN;
 
-        /* STS_HW_CONDITIONS */
-        status = twl4030_readb(twl, TWL4030_MODULE_PM_MASTER, 0x0f);
+        /*
+         * For ID/VBUS sensing, see manual section 15.4.8 ...
+         * except when using only battery backup power, two
+         * comparators produce VBUS_PRES and ID_PRES signals,
+         * which don't match docs elsewhere.  But ... BIT(7)
+         * and BIT(2) of STS_HW_CONDITIONS, respectively, do
+         * seem to match up.  If either is true the USB_PRES
+         * signal is active, the OTG module is activated, and
+         * its interrupt may be raised (may wake the system).
+         */
+        status = twl4030_readb(twl, TWL4030_MODULE_PM_MASTER,
+                        STS_HW_CONDITIONS);
         if (status < 0)
                 dev_err(twl->dev, "USB link status err %d\n", status);
-        else if (status & BIT(7))
-                linkstat = USB_LINK_VBUS;
-        else if (status & BIT(2))
-                linkstat = USB_LINK_ID;
-        else
+        else if (status & (BIT(7) | BIT(2))) {
+                if (status & BIT(2))
+                        linkstat = USB_LINK_ID;
+                else
+                        linkstat = USB_LINK_VBUS;
+        } else
                 linkstat = USB_LINK_NONE;
 
         dev_dbg(twl->dev, "HW_CONDITIONS 0x%02x/%d; link %d\n",