serial: samsung: wait for transfer completion before clock disable

commit 1ff383a4c3eda8893ec61b02831826e1b1f46b41 upstream.

This patch adds waiting until transmit buffer and shifter will be empty
before clock disabling.

Without this fix it's possible to have clock disabled while data was
not transmited yet, which causes unproper state of TX line and problems
in following data transfers.

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index b31f1c3..626e75b 100644 (file)
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -519,11 +519,15 @@ static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
                              unsigned int old)
 {
        struct s3c24xx_uart_port *ourport = to_ourport(port);
+       int timeout = 10000;
 
        ourport->pm_level = level;
 
        switch (level) {
        case 3:
+               while (--timeout && !s3c24xx_serial_txempty_nofifo(port))
+                       udelay(100);
+
                if (!IS_ERR(ourport->baudclk) && ourport->baudclk != NULL)
                        clk_disable(ourport->baudclk);