serial: sirf: fix endless loop bug in uart receive tasklet

In special condition, when cpu schedule into rx_tmo_process_tl or
rx_dma_complete_tl and all the receive dma tasks have done, it will
go into endless loop because no dma task cookie status be changed.
Signed-off-by: NQipan Li <Qipan.Li@csr.com>
Signed-off-by: NBarry Song <Baohua.Song@csr.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sirfsoc_uart.c

@@ -488,6 +488,7 @@ static void sirfsoc_rx_tmo_process_tl(unsigned long param)
 	unsigned int count;
 	struct dma_tx_state tx_state;
 	unsigned long flags;
+	int i = 0;
 
 	spin_lock_irqsave(&port->lock, flags);
 	while (DMA_COMPLETE == dmaengine_tx_status(sirfport->rx_dma_chan,
@@ -497,6 +498,9 @@ static void sirfsoc_rx_tmo_process_tl(unsigned long param)
 					SIRFSOC_RX_DMA_BUF_SIZE);
 		sirfport->rx_completed++;
 		sirfport->rx_completed %= SIRFSOC_RX_LOOP_BUF_CNT;
+		i++;
+		if (i > SIRFSOC_RX_LOOP_BUF_CNT)
+			break;
 	}
 	count = CIRC_CNT(sirfport->rx_dma_items[sirfport->rx_issued].xmit.head,
 		sirfport->rx_dma_items[sirfport->rx_issued].xmit.tail,
@@ -713,6 +717,8 @@ static void sirfsoc_uart_rx_dma_complete_tl(unsigned long param)
 	struct sirfsoc_int_en *uint_en = &sirfport->uart_reg->uart_int_en;
 	struct dma_tx_state tx_state;
 	unsigned long flags;
+	int i = 0;
+
 	spin_lock_irqsave(&port->lock, flags);
 	while (DMA_COMPLETE == dmaengine_tx_status(sirfport->rx_dma_chan,
 		sirfport->rx_dma_items[sirfport->rx_completed].cookie,
@@ -726,6 +732,9 @@ static void sirfsoc_uart_rx_dma_complete_tl(unsigned long param)
 		else
 			sirfport->rx_completed++;
 		sirfport->rx_completed %= SIRFSOC_RX_LOOP_BUF_CNT;
+		i++;
+		if (i > SIRFSOC_RX_LOOP_BUF_CNT)
+			break;
 	}
 	spin_unlock_irqrestore(&port->lock, flags);
 	tty_flip_buffer_push(&port->state->port);