USB: HWA: fix device probe failure

This patch fixes a race condition that caused the HWA_HC interface probe
function to occasionally fail.  The HWA_HC would attempt to register
itself with the HWA_RC by searching for a uwb_rc class device with the
same parent device ptr.  If the probe function for the HWA_RC interface
had yet to run, the uwb_rc class device would not have been created
causing the look up to fail and the HWA_HC probe function to return an
error causing the device to be unusable.

The fix is for the HWA to delay registering with the HWA_RC until
receiving the command from userspace to start the wireless channel.  It
is the responsibility of userspace to ensure that the uwb_rc class
device has been created before starting the HWA channel.

Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 27 insertions, 0 deletions

diff --git a/drivers/usb/wusbcore/mmc.c b/drivers/usb/wusbcore/mmc.c
index 021467f86d9e..b71760c8d3ad 100644
--- a/drivers/usb/wusbcore/mmc.c
+++ b/drivers/usb/wusbcore/mmc.c
@@ -195,6 +195,7 @@ int wusbhc_start(struct wusbhc *wusbhc)
 	struct device *dev = wusbhc->dev;
 
 	WARN_ON(wusbhc->wuie_host_info != NULL);
+	BUG_ON(wusbhc->uwb_rc == NULL);
 
 	result = wusbhc_rsv_establish(wusbhc);
 	if (result < 0) {
@@ -276,12 +277,38 @@ int wusbhc_chid_set(struct wusbhc *wusbhc, const struct wusb_ckhdid *chid)
 		}
 		wusbhc->chid = *chid;
 	}
+
+	/* register with UWB if we haven't already since we are about to start
+	    the radio. */
+	if ((chid) && (wusbhc->uwb_rc == NULL)) {
+		wusbhc->uwb_rc = uwb_rc_get_by_grandpa(wusbhc->dev->parent);
+		if (wusbhc->uwb_rc == NULL) {
+			result = -ENODEV;
+			dev_err(wusbhc->dev, "Cannot get associated UWB Host Controller\n");
+			goto error_rc_get;
+		}
+
+		result = wusbhc_pal_register(wusbhc);
+		if (result < 0) {
+			dev_err(wusbhc->dev, "Cannot register as a UWB PAL\n");
+			goto error_pal_register;
+		}
+	}
 	mutex_unlock(&wusbhc->mutex);
 
 	if (chid)
 		result = uwb_radio_start(&wusbhc->pal);
 	else
 		uwb_radio_stop(&wusbhc->pal);
+
+	return result;
+
+error_pal_register:
+	uwb_rc_put(wusbhc->uwb_rc);
+	wusbhc->uwb_rc = NULL;
+error_rc_get:
+	mutex_unlock(&wusbhc->mutex);
+
 	return result;
 }
 EXPORT_SYMBOL_GPL(wusbhc_chid_set);