[PATCH] USB ATM: fix line resync logic

We map states 0x00 and 0x10 to the ATM_PHY_SIG_LOST flag.  The current logic fails to
resync the line if we get state 0x10 followed by 0x00, since we only resync the line
when the state is 0x00 and the flag changed.  Doubly fixed by (1) always resyncing the
line when the state is 0x00 even if the state didn't change, and (2) keeping track of
the last state, not just the flag.  We do (2) as well as (1) in order to get better log
messages.

This is a tweaked version of the original patch by Aurelio Arroyo.
Signed-off-by: Duncan Sands <baldrick@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/atm/speedtch.c

@@ -100,6 +100,8 @@ struct speedtch_instance_data {
 
 	struct work_struct status_checker;
 
+	unsigned char last_status;
+
 	int poll_delay; /* milliseconds */
 
 	struct timer_list resubmit_timer;
@@ -423,7 +425,8 @@ static void speedtch_check_status(struct speedtch_instance_data *instance)
 	struct usbatm_data *usbatm = instance->usbatm;
 	struct atm_dev *atm_dev = usbatm->atm_dev;
 	unsigned char *buf = instance->scratch_buffer;
-	int ret;
+	int down_speed, up_speed, ret;
+	unsigned char status;
 
 	atm_dbg(usbatm, "%s entered\n", __func__);
 
@@ -436,37 +439,34 @@ static void speedtch_check_status(struct speedtch_instance_data *instance)
 
 	instance->poll_delay = max(instance->poll_delay / 2, MIN_POLL_DELAY);
 
-	atm_dbg(usbatm, "%s: line state %02x\n", __func__, buf[OFFSET_7]);
+	status = buf[OFFSET_7];
+
+	atm_dbg(usbatm, "%s: line state %02x\n", __func__, status);
 
-	switch (buf[OFFSET_7]) {
+	if ((status != instance->last_status) || !status) {
+		switch (status) {
 		case 0:
-		if (atm_dev->signal != ATM_PHY_SIG_LOST) {
 			atm_dev->signal = ATM_PHY_SIG_LOST;
+			if (instance->last_status)
 				atm_info(usbatm, "ADSL line is down\n");
-			/* It'll never resync again unless we ask it to... */
+			/* It may never resync again unless we ask it to... */
 			ret = speedtch_start_synchro(instance);
-		}
 			break;
 
 		case 0x08:
-		if (atm_dev->signal != ATM_PHY_SIG_UNKNOWN) {
 			atm_dev->signal = ATM_PHY_SIG_UNKNOWN;
 			atm_info(usbatm, "ADSL line is blocked?\n");
-		}
 			break;
 
 		case 0x10:
-		if (atm_dev->signal != ATM_PHY_SIG_LOST) {
 			atm_dev->signal = ATM_PHY_SIG_LOST;
 			atm_info(usbatm, "ADSL line is synchronising\n");
-		}
 			break;
 
 		case 0x20:
-		if (atm_dev->signal != ATM_PHY_SIG_FOUND) {
-			int down_speed = buf[OFFSET_b] | (buf[OFFSET_b + 1] << 8)
+			down_speed = buf[OFFSET_b] | (buf[OFFSET_b + 1] << 8)
 				| (buf[OFFSET_b + 2] << 16) | (buf[OFFSET_b + 3] << 24);
-			int up_speed = buf[OFFSET_b + 4] | (buf[OFFSET_b + 5] << 8)
+			up_speed = buf[OFFSET_b + 4] | (buf[OFFSET_b + 5] << 8)
 				| (buf[OFFSET_b + 6] << 16) | (buf[OFFSET_b + 7] << 24);
 
 			if (!(down_speed & 0x0000ffff) && !(up_speed & 0x0000ffff)) {
@@ -480,16 +480,16 @@ static void speedtch_check_status(struct speedtch_instance_data *instance)
 			atm_info(usbatm,
 				 "ADSL line is up (%d kb/s down | %d kb/s up)\n",
 				 down_speed, up_speed);
-		}
 			break;
 
 		default:
-		if (atm_dev->signal != ATM_PHY_SIG_UNKNOWN) {
 			atm_dev->signal = ATM_PHY_SIG_UNKNOWN;
-			atm_info(usbatm, "Unknown line state %02x\n", buf[OFFSET_7]);
-		}
+			atm_info(usbatm, "Unknown line state %02x\n", status);
 			break;
 		}
+
+		instance->last_status = status;
+	}
 }
 
 static void speedtch_status_poll(unsigned long data)
@@ -728,6 +728,7 @@ static int speedtch_bind(struct usbatm_data *usbatm,
 
 	instance->status_checker.timer.function = speedtch_status_poll;
 	instance->status_checker.timer.data = (unsigned long)instance;
+	instance->last_status = 0xff;
 	instance->poll_delay = MIN_POLL_DELAY;
 
 	init_timer(&instance->resubmit_timer);