serial: sh-sci: fix deadlock when resuming from S3 sleep

S3 sleep invokes the shutdown callback of the sh-sci driver, which
suspends the clocks until they are reactivated by a call to startup.
However, before the latter is invoked, sci_set_termios may be called on
the port by uart_resume_port. In such cases it will endlessly wait for
the TEND bit to raise, which will never happen since the clocks are
disabled.

This patch ensures that clocks are enabled when ports registers are
manipulated within sci_set_termios.

Signed-off-by: Alexandre Courbot <gnurou@gmail.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 0257fd5ede52bf0e6d6ea5d329d9d17ae11768a1..eb7958c675a80c7989ffeaced1fe65ef37ce0f6e 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1504,6 +1504,9 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
        if (likely(baud && port->uartclk))
                t = sci_scbrr_calc(s->cfg->scbrr_algo_id, baud, port->uartclk);
 
+       if (s->enable)
+               s->enable(port);
+
        do {
                status = sci_in(port, SCxSR);
        } while (!(status & SCxSR_TEND(port)));
@@ -1571,6 +1574,9 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
 
        if ((termios->c_cflag & CREAD) != 0)
                sci_start_rx(port);
+
+       if (s->disable)
+               s->disable(port);
 }
 
 static const char *sci_type(struct uart_port *port)