serial: lantiq: Add SMP support

The existing driver can only support single core SoC. But new multicore
platforms which reuse the same driver/IP need SMP support. This patch adds
multicore support in the driver.
Signed-off-by: Rahul Tanwar <rahul.tanwar@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Link: https://lore.kernel.org/r/7912786cccad60c72b20ea724af1def505ab22aa.1565160764.git.rahul.tanwar@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/lantiq.c

@@ -99,7 +99,6 @@
 static void lqasc_tx_chars(struct uart_port *port);
 static struct ltq_uart_port *lqasc_port[MAXPORTS];
 static struct uart_driver lqasc_reg;
-static DEFINE_SPINLOCK(ltq_asc_lock);
 
 struct ltq_uart_port {
 	struct uart_port	port;
@@ -110,6 +109,7 @@ struct ltq_uart_port {
 	unsigned int		tx_irq;
 	unsigned int		rx_irq;
 	unsigned int		err_irq;
+	spinlock_t		lock; /* exclusive access for multi core */
 };
 
 static inline void asc_update_bits(u32 clear, u32 set, void __iomem *reg)
@@ -135,9 +135,11 @@ static void
 lqasc_start_tx(struct uart_port *port)
 {
 	unsigned long flags;
-	spin_lock_irqsave(&ltq_asc_lock, flags);
+	struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
+
+	spin_lock_irqsave(&ltq_port->lock, flags);
 	lqasc_tx_chars(port);
-	spin_unlock_irqrestore(&ltq_asc_lock, flags);
+	spin_unlock_irqrestore(&ltq_port->lock, flags);
 	return;
 }
 
@@ -245,9 +247,11 @@ lqasc_tx_int(int irq, void *_port)
 {
 	unsigned long flags;
 	struct uart_port *port = (struct uart_port *)_port;
-	spin_lock_irqsave(&ltq_asc_lock, flags);
+	struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
+
+	spin_lock_irqsave(&ltq_port->lock, flags);
 	__raw_writel(ASC_IRNCR_TIR, port->membase + LTQ_ASC_IRNCR);
-	spin_unlock_irqrestore(&ltq_asc_lock, flags);
+	spin_unlock_irqrestore(&ltq_port->lock, flags);
 	lqasc_start_tx(port);
 	return IRQ_HANDLED;
 }
@@ -257,11 +261,13 @@ lqasc_err_int(int irq, void *_port)
 {
 	unsigned long flags;
 	struct uart_port *port = (struct uart_port *)_port;
-	spin_lock_irqsave(&ltq_asc_lock, flags);
+	struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
+
+	spin_lock_irqsave(&ltq_port->lock, flags);
 	/* clear any pending interrupts */
 	asc_update_bits(0, ASCWHBSTATE_CLRPE | ASCWHBSTATE_CLRFE |
 		ASCWHBSTATE_CLRROE, port->membase + LTQ_ASC_WHBSTATE);
-	spin_unlock_irqrestore(&ltq_asc_lock, flags);
+	spin_unlock_irqrestore(&ltq_port->lock, flags);
 	return IRQ_HANDLED;
 }
 
@@ -270,10 +276,12 @@ lqasc_rx_int(int irq, void *_port)
 {
 	unsigned long flags;
 	struct uart_port *port = (struct uart_port *)_port;
-	spin_lock_irqsave(&ltq_asc_lock, flags);
+	struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
+
+	spin_lock_irqsave(&ltq_port->lock, flags);
 	__raw_writel(ASC_IRNCR_RIR, port->membase + LTQ_ASC_IRNCR);
 	lqasc_rx_chars(port);
-	spin_unlock_irqrestore(&ltq_asc_lock, flags);
+	spin_unlock_irqrestore(&ltq_port->lock, flags);
 	return IRQ_HANDLED;
 }
 
@@ -307,11 +315,13 @@ lqasc_startup(struct uart_port *port)
 {
 	struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
 	int retval;
+	unsigned long flags;
 
 	if (!IS_ERR(ltq_port->clk))
 		clk_prepare_enable(ltq_port->clk);
 	port->uartclk = clk_get_rate(ltq_port->freqclk);
 
+	spin_lock_irqsave(&ltq_port->lock, flags);
 	asc_update_bits(ASCCLC_DISS | ASCCLC_RMCMASK, (1 << ASCCLC_RMCOFFSET),
 		port->membase + LTQ_ASC_CLC);
 
@@ -331,6 +341,8 @@ lqasc_startup(struct uart_port *port)
 	asc_update_bits(0, ASCCON_M_8ASYNC | ASCCON_FEN | ASCCON_TOEN |
 		ASCCON_ROEN, port->membase + LTQ_ASC_CON);
 
+	spin_unlock_irqrestore(&ltq_port->lock, flags);
+
 	retval = request_irq(ltq_port->tx_irq, lqasc_tx_int,
 		0, "asc_tx", port);
 	if (retval) {
@@ -367,15 +379,19 @@ static void
 lqasc_shutdown(struct uart_port *port)
 {
 	struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
+	unsigned long flags;
+
 	free_irq(ltq_port->tx_irq, port);
 	free_irq(ltq_port->rx_irq, port);
 	free_irq(ltq_port->err_irq, port);
 
+	spin_lock_irqsave(&ltq_port->lock, flags);
 	__raw_writel(0, port->membase + LTQ_ASC_CON);
 	asc_update_bits(ASCRXFCON_RXFEN, ASCRXFCON_RXFFLU,
 		port->membase + LTQ_ASC_RXFCON);
 	asc_update_bits(ASCTXFCON_TXFEN, ASCTXFCON_TXFFLU,
 		port->membase + LTQ_ASC_TXFCON);
+	spin_unlock_irqrestore(&ltq_port->lock, flags);
 	if (!IS_ERR(ltq_port->clk))
 		clk_disable_unprepare(ltq_port->clk);
 }
@@ -390,6 +406,7 @@ lqasc_set_termios(struct uart_port *port,
 	unsigned int baud;
 	unsigned int con = 0;
 	unsigned long flags;
+	struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
 
 	cflag = new->c_cflag;
 	iflag = new->c_iflag;
@@ -443,7 +460,7 @@ lqasc_set_termios(struct uart_port *port,
 	/* set error signals  - framing, parity  and overrun, enable receiver */
 	con |= ASCCON_FEN | ASCCON_TOEN | ASCCON_ROEN;
 
-	spin_lock_irqsave(&ltq_asc_lock, flags);
+	spin_lock_irqsave(&ltq_port->lock, flags);
 
 	/* set up CON */
 	asc_update_bits(0, con, port->membase + LTQ_ASC_CON);
@@ -471,7 +488,7 @@ lqasc_set_termios(struct uart_port *port,
 	/* enable rx */
 	__raw_writel(ASCWHBSTATE_SETREN, port->membase + LTQ_ASC_WHBSTATE);
 
-	spin_unlock_irqrestore(&ltq_asc_lock, flags);
+	spin_unlock_irqrestore(&ltq_port->lock, flags);
 
 	/* Don't rewrite B0 */
 	if (tty_termios_baud_rate(new))
@@ -589,17 +606,14 @@ lqasc_console_putchar(struct uart_port *port, int ch)
 static void lqasc_serial_port_write(struct uart_port *port, const char *s,
 				    u_int count)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ltq_asc_lock, flags);
 	uart_console_write(port, s, count, lqasc_console_putchar);
-	spin_unlock_irqrestore(&ltq_asc_lock, flags);
 }
 
 static void
 lqasc_console_write(struct console *co, const char *s, u_int count)
 {
 	struct ltq_uart_port *ltq_port;
+	unsigned long flags;
 
 	if (co->index >= MAXPORTS)
 		return;
@@ -608,7 +622,9 @@ lqasc_console_write(struct console *co, const char *s, u_int count)
 	if (!ltq_port)
 		return;
 
+	spin_lock_irqsave(&ltq_port->lock, flags);
 	lqasc_serial_port_write(&ltq_port->port, s, count);
+	spin_unlock_irqrestore(&ltq_port->lock, flags);
 }
 
 static int __init
@@ -766,6 +782,7 @@ lqasc_probe(struct platform_device *pdev)
 	ltq_port->rx_irq = irqres[1].start;
 	ltq_port->err_irq = irqres[2].start;
 
+	spin_lock_init(&ltq_port->lock);
 	lqasc_port[line] = ltq_port;
 	platform_set_drvdata(pdev, ltq_port);