serial: samsung: wait for transfer completion before clock disable

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.

Cc: stable@vger.kernel.org
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 1ff383a4c3eda8893ec61b02831826e1b1f46b41)
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/drivers/serial/samsung.c b/drivers/serial/samsung.c
index 1523e8d9ae7789b2a50dc04498cb3fa586a163d0..fe6ef16b59569aa4455efa602ad35598c04d6e4e 100644 (file)
--- a/drivers/serial/samsung.c
+++ b/drivers/serial/samsung.c
@@ -443,11 +443,15 @@ 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);