Blackfin Serial Driver: Use timer to poll CTS PIN instead of workqueue.

This allows other threads to run when the serial driver polls the CTS
PIN in a loop.

Signed-off-by: Sonic Zhang <[e-mail]>
Signed-off-by: Bryan Wu <[e-mail]>

drivers/serial/bfin_5xx.c

···
 #define DMA_RX_YCOUNT		(PAGE_SIZE / DMA_RX_XCOUNT)
 
 #define DMA_RX_FLUSH_JIFFIES	(HZ / 50)
+#define CTS_CHECK_JIFFIES	(HZ / 50)
 
 #ifdef CONFIG_SERIAL_BFIN_DMA
 static void bfin_serial_dma_tx_chars(struct bfin_serial_port *uart);
···
 {
 	struct circ_buf *xmit = &uart->port.info->xmit;
 
-	if (uart->port.x_char) {
-		UART_PUT_CHAR(uart, uart->port.x_char);
-		uart->port.icount.tx++;
-		uart->port.x_char = 0;
-	}
 	/*
 	 * Check the modem control lines before
 	 * transmitting anything.
···
 	if (uart_circ_empty(xmit) || uart_tx_stopped(&uart->port)) {
 		bfin_serial_stop_tx(&uart->port);
 		return;
+	}
+
+	if (uart->port.x_char) {
+		UART_PUT_CHAR(uart, uart->port.x_char);
+		uart->port.icount.tx++;
+		uart->port.x_char = 0;
 	}
 
 	while ((UART_GET_LSR(uart) & THRE) && xmit->tail != xmit->head) {
···
 }
 #endif
 
-#ifdef CONFIG_SERIAL_BFIN_CTSRTS
-static void bfin_serial_do_work(struct work_struct *work)
-{
-	struct bfin_serial_port *uart = container_of(work, struct bfin_serial_port, cts_workqueue);
-
-	bfin_serial_mctrl_check(uart);
-}
-#endif
-
 #ifdef CONFIG_SERIAL_BFIN_DMA
 static void bfin_serial_dma_tx_chars(struct bfin_serial_port *uart)
 {
 	struct circ_buf *xmit = &uart->port.info->xmit;
 
 	uart->tx_done = 0;
+
+	/*
+	 * Check the modem control lines before
+	 * transmitting anything.
+	 */
+	bfin_serial_mctrl_check(uart);
 
 	if (uart_circ_empty(xmit) || uart_tx_stopped(&uart->port)) {
 		uart->tx_count = 0;
···
 		uart->port.icount.tx++;
 		uart->port.x_char = 0;
 	}
-
-	/*
-	 * Check the modem control lines before
-	 * transmitting anything.
-	 */
-	bfin_serial_mctrl_check(uart);
 
 	uart->tx_count = CIRC_CNT(xmit->head, xmit->tail, UART_XMIT_SIZE);
 	if (uart->tx_count > (UART_XMIT_SIZE - xmit->tail))
···
 	uart_handle_cts_change(&uart->port, status & TIOCM_CTS);
 	if (!(status & TIOCM_CTS)) {
 		tty->hw_stopped = 1;
-		schedule_work(&uart->cts_workqueue);
+		uart->cts_timer.data = (unsigned long)(uart);
+		uart->cts_timer.function = (void *)bfin_serial_mctrl_check;
+		uart->cts_timer.expires = jiffies + CTS_CHECK_JIFFIES;
+		add_timer(&(uart->cts_timer));
 	} else {
 		tty->hw_stopped = 0;
 	}
···
 		init_timer(&(bfin_serial_ports[i].rx_dma_timer));
 #endif
 #ifdef CONFIG_SERIAL_BFIN_CTSRTS
-		INIT_WORK(&bfin_serial_ports[i].cts_workqueue, bfin_serial_do_work);
+		init_timer(&(bfin_serial_ports[i].cts_timer));
 		bfin_serial_ports[i].cts_pin	    =
 			bfin_serial_resource[i].uart_cts_pin;
 		bfin_serial_ports[i].rts_pin	    =

include/asm-blackfin/mach-bf527/bfin_serial_5xx.h

···
 	struct work_struct tx_dma_workqueue;
 #endif
 #ifdef CONFIG_SERIAL_BFIN_CTSRTS
-	struct work_struct cts_workqueue;
+	struct timer_list cts_timer;
 	int cts_pin;
 	int rts_pin;
 #endif

include/asm-blackfin/mach-bf533/bfin_serial_5xx.h

···
 # endif
 #endif
 #ifdef CONFIG_SERIAL_BFIN_CTSRTS
-	struct work_struct 	cts_workqueue;
+	struct timer_list       cts_timer;
 	int			cts_pin;
 	int			rts_pin;
 #endif

include/asm-blackfin/mach-bf537/bfin_serial_5xx.h

···
 	struct work_struct	tx_dma_workqueue;
 #endif
 #ifdef CONFIG_SERIAL_BFIN_CTSRTS
-	struct work_struct 	cts_workqueue;
+	struct timer_list 	cts_timer;
 	int		cts_pin;
 	int 		rts_pin;
 #endif

include/asm-blackfin/mach-bf548/bfin_serial_5xx.h

···
 	struct work_struct	tx_dma_workqueue;
 #endif
 #ifdef CONFIG_SERIAL_BFIN_CTSRTS
-	struct work_struct 	cts_workqueue;
+	struct timer_list 	cts_timer;
 	int		cts_pin;
 	int 		rts_pin;
 #endif

include/asm-blackfin/mach-bf561/bfin_serial_5xx.h

···
 # endif
 #endif
 #ifdef CONFIG_SERIAL_BFIN_CTSRTS
-	struct work_struct 	cts_workqueue;
+	struct timer_list       cts_timer;
 	int			cts_pin;
 	int			rts_pin;
 #endif