wimax/i2400m: fix the bootmode RX deadlock in SDIO driver

i2400ms_bus_bm_wait_for_ack() causes a race condition. It happens
because this function clears i2400ms->bm_ack_size before waiting for
an interrupt, which is set by the interrupt service routine i2400ms_rx()
to indicate reception and size of received data; thus, if the interrupt
came right before the clearing/waiting, it is lost.

The fix is clear the bm_ack_size to -EINPROGRESS before we are enabling
the RX interrupt configuration in i2400ms_rx_setup(). Then everytime
when the interrupt service routine i2400ms_rx() is invoked during bootmode,
bm_ack_size is updated with the actual rx_size and it is cleared to
-EINPROGRESS again after the RX data is handled.
Signed-off-by: Cindy H Kao <cindy.h.kao@intel.com>
Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>

drivers/net/wimax/i2400m/sdio-fw.c

@@ -177,10 +177,6 @@ ssize_t i2400ms_bus_bm_wait_for_ack(struct i2400m *i2400m,
 	d_fnstart(5, dev, "(i2400m %p ack %p size %zu)\n",
 		  i2400m, ack, ack_size);
 
-	spin_lock(&i2400m->rx_lock);
-	i2400ms->bm_ack_size = -EINPROGRESS;
-	spin_unlock(&i2400m->rx_lock);
-
 	result = wait_event_timeout(i2400ms->bm_wfa_wq,
 				    i2400ms->bm_ack_size != -EINPROGRESS,
 				    2 * HZ);
@@ -199,6 +195,10 @@ ssize_t i2400ms_bus_bm_wait_for_ack(struct i2400m *i2400m,
 		size = min(ack_size, i2400ms->bm_ack_size);
 		memcpy(ack, i2400m->bm_ack_buf, size);
 	}
+	/*
+	 * Remember always to clear the bm_ack_size to -EINPROGRESS
+	 * after the RX data is processed
+	 */
 	i2400ms->bm_ack_size = -EINPROGRESS;
 	spin_unlock(&i2400m->rx_lock);
 

drivers/net/wimax/i2400m/sdio-rx.c

@@ -234,6 +234,13 @@ int i2400ms_rx_setup(struct i2400ms *i2400ms)
 	init_waitqueue_head(&i2400ms->bm_wfa_wq);
 	spin_lock(&i2400m->rx_lock);
 	i2400ms->bm_wait_result = -EINPROGRESS;
+	/*
+	 * Before we are about to enable the RX interrupt, make sure
+	 * bm_ack_size is cleared to -EINPROGRESS which indicates
+	 * no RX interrupt happened yet or the previous interrupt
+	 * has been handled, we are ready to take the new interrupt
+	 */
+	i2400ms->bm_ack_size = -EINPROGRESS;
 	spin_unlock(&i2400m->rx_lock);
 
 	sdio_claim_host(func);