[PATCH] atmel_serial oops when peripheral clock misconfigured

[Douglas Gilbert <dgilbert@interlog.com>]

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In lk 3.7.0-rc4 when a peripheral clock is not found for
a serial port the atmel_serial driver brings down the
kernel with an oops during boot-up. This impacts the
Atmel AT91 family of MCUs.

For example, arch/arm/mach-at91/at91sam9x5.c does not
specify properly the peripheral clocks for the UTXD0/URXD0
and UTXD1/URXD1 serial ports. Selecting either of those
ports in a dts file will crash the kernel. at91sam9x5.c needs
to be fixed but stopping atmel_serial crashing the kernel is
more urgent.

Patch attached for your consideration.

Signed-of-by: Douglas Gilbert <dgilbert@interlog.com>

[-- Attachment #2: atmel_serial_clk_oops.patch --]
[-- Type: text/x-patch, Size: 2246 bytes --]

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 3d7e1ee..cc385e0 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -1457,8 +1457,9 @@ static void __devinit atmel_of_init_port(struct atmel_uart_port *atmel_port,
 
 /*
  * Configure the port from the platform device resource info.
+ * Returns 0 for success or 1 in case of error.
  */
-static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
+static int __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
 				      struct platform_device *pdev)
 {
 	struct uart_port *port = &atmel_port->uart;
@@ -1496,6 +1497,8 @@ static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
 	/* for console, the clock could already be configured */
 	if (!atmel_port->clk) {
 		atmel_port->clk = clk_get(&pdev->dev, "usart");
+		if (IS_ERR(atmel_port->clk))
+			return 1;	/* peripheral clock not found */
 		clk_enable(atmel_port->clk);
 		port->uartclk = clk_get_rate(atmel_port->clk);
 		clk_disable(atmel_port->clk);
@@ -1511,6 +1514,7 @@ static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
 	} else {
 		atmel_port->tx_done_mask = ATMEL_US_TXRDY;
 	}
+	return 0;
 }
 
 /*
@@ -1666,13 +1670,18 @@ static int __init atmel_console_init(void)
 		struct atmel_uart_data *pdata =
 			atmel_default_console_device->dev.platform_data;
 		int id = pdata->num;
+		int ret;
 		struct atmel_uart_port *port = &atmel_ports[id];
 
 		port->backup_imr = 0;
 		port->uart.line = id;
 
 		add_preferred_console(ATMEL_DEVICENAME, id, NULL);
-		atmel_init_port(port, atmel_default_console_device);
+		ret = atmel_init_port(port, atmel_default_console_device);
+		if (ret) {
+			pr_err("No peripheral clock for Atmel console ??\n");
+			return -EINVAL;
+		}
 		register_console(&atmel_console);
 	}
 
@@ -1803,7 +1812,12 @@ static int __devinit atmel_serial_probe(struct platform_device *pdev)
 	port->backup_imr = 0;
 	port->uart.line = ret;
 
-	atmel_init_port(port, pdev);
+	ret = atmel_init_port(port, pdev);
+	if (ret) {
+		ret = -EINVAL;
+		pr_err("peripheral clock not found for serial port\n");
+		goto err;
+	}
 
 	if (!atmel_use_dma_rx(&port->uart)) {
 		ret = -ENOMEM;