ipack/devices/ipoctal: protect the channel data processing with a spinlock

We protect important data such as TX buffer pointer, nb_bytes counter and status
registers of the device, from accessing several times at the same time.
Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/ipack/devices/ipoctal.c

@@ -191,6 +191,8 @@ static void ipoctal_irq_channel(struct ipoctal_channel *channel)
 	tty = tty_port_tty_get(&channel->tty_port);
 	if (!tty)
 		return;
+
+	spin_lock(&channel->lock);
 	/* The HW is organized in pair of channels.  See which register we need
 	 * to read from */
 	isr = ioread8(&channel->block_regs->r.isr);
@@ -216,6 +218,7 @@ static void ipoctal_irq_channel(struct ipoctal_channel *channel)
 
 	tty_flip_buffer_push(tty);
 	tty_kref_put(tty);
+	spin_unlock(&channel->lock);
 }
 
 static irqreturn_t ipoctal_irq_handler(void *arg)