Re: [PATCH v2] serial: samsung: Fixed wrong comparison for baudclk_rate

[Russell King - ARM Linux <linux@arm.linux.org.uk>]

On Tue, May 15, 2012 at 09:37:16PM +0900, Kyoungil Kim wrote:
> port->baudclk_rate should be compared to the rate of port->baudclk,
> because port->baudclk_rate was assigned as the rate of port->baudclk previously.
> So to check that the current baudclk rate is same as previous rate,
> the target of comparison sholud be the rate of port->baudclk.
> 
> Signed-off-by: Jun-Ho, Yoon <junho78.yoon@samsung.com>
> Signed-off-by: Kyoungil Kim <ki0351.kim@samsung.com>
> ---
>  drivers/tty/serial/samsung.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> index d8b0aee..6a6a86a 100644
> --- a/drivers/tty/serial/samsung.c
> +++ b/drivers/tty/serial/samsung.c
> @@ -1014,10 +1014,10 @@ static int s3c24xx_serial_cpufreq_transition(struct notifier_block *nb,
>  	 * a disturbance in the clock-rate over the change.
>  	 */
>  
> -	if (IS_ERR(port->clk))
> +	if (IS_ERR(port->baudclk) || port->baudclk == NULL)

Still no.  Why are you wanting to detect a NULL baud clock?

As I said, drivers have no business interpreting anything but IS_ERR(clk)
as being an error.  They should not make any other assumptions.

Now that I look at this driver, it makes this mistake all over the place.
This needs to be fixed.  Something like the below should do it.  Please
check.

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index d8b0aee..6a952b1 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -529,7 +529,7 @@ static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
 
 	switch (level) {
 	case 3:
-		if (!IS_ERR(ourport->baudclk) && ourport->baudclk != NULL)
+		if (!IS_ERR(ourport->baudclk))
 			clk_disable(ourport->baudclk);
 
 		clk_disable(ourport->clk);
@@ -538,7 +538,7 @@ static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
 	case 0:
 		clk_enable(ourport->clk);
 
-		if (!IS_ERR(ourport->baudclk) && ourport->baudclk != NULL)
+		if (!IS_ERR(ourport->baudclk))
 			clk_enable(ourport->baudclk);
 
 		break;
@@ -713,9 +713,9 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
 	if (ourport->baudclk != clk) {
 		s3c24xx_serial_setsource(port, clk_sel);
 
-		if (ourport->baudclk != NULL && !IS_ERR(ourport->baudclk)) {
+		if (!IS_ERR(ourport->baudclk)) {
 			clk_disable(ourport->baudclk);
-			ourport->baudclk  = NULL;
+			ourport->baudclk = ERR_PTR(-EINVAL);
 		}
 
 		clk_enable(clk);
@@ -1160,6 +1160,9 @@ static ssize_t s3c24xx_serial_show_clksrc(struct device *dev,
 	struct uart_port *port = s3c24xx_dev_to_port(dev);
 	struct s3c24xx_uart_port *ourport = to_ourport(port);
 
+	if (IS_ERR(ourport->baudclk))
+		return -EINVAL;
+
 	return snprintf(buf, PAGE_SIZE, "* %s\n", ourport->baudclk->name);
 }
 
@@ -1200,6 +1203,7 @@ static int s3c24xx_serial_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
+	ourport->baudclk = ERR_PTR(-EINVAL);
 	ourport->info = ourport->drv_data->info;
 	ourport->cfg = (pdev->dev.platform_data) ?
 			(struct s3c2410_uartcfg *)pdev->dev.platform_data :