Since serial devices are powered down when not in use and some of those
devices cannot be accessed when powered down, we need to enable power
around calls to get_mcrtl() when dumping port state via uart_line_info().
This resolves hangs observed on some machines while reading serial device
registers when a port is powered off.
Signed-off-by: George G. Davis <[email protected]>
drivers/serial/serial_core.c | 11 +++++++++++
1 files changed, 11 insertions(+)
Index: linux-2.6/drivers/serial/serial_core.c
===================================================================
--- linux-2.6.orig/drivers/serial/serial_core.c
+++ linux-2.6/drivers/serial/serial_core.c
@@ -1652,6 +1652,7 @@ static const char *uart_type(struct uart
static int uart_line_info(char *buf, struct uart_driver *drv, int i)
{
struct uart_state *state = drv->state + i;
+ int pm_state;
struct uart_port *port = state->port;
char stat_buf[32];
unsigned int status;
@@ -1674,9 +1675,16 @@ static int uart_line_info(char *buf, str
if(capable(CAP_SYS_ADMIN))
{
+ mutex_lock(&state->mutex);
+ pm_state = state->pm_state;
+ if (pm_state)
+ uart_change_pm(state, 0);
spin_lock_irq(&port->lock);
status = port->ops->get_mctrl(port);
spin_unlock_irq(&port->lock);
+ if (pm_state)
+ uart_change_pm(state, pm_state);
+ mutex_unlock(&state->mutex);
ret += sprintf(buf + ret, " tx:%d rx:%d",
port->icount.tx, port->icount.rx);
@@ -2071,6 +2079,9 @@ uart_configure_port(struct uart_driver *
uart_report_port(drv, port);
+ /* Power up port for set_mctrl() */
+ uart_change_pm(state, 0);
+
/*
* Ensure that the modem control lines are de-activated.
* We probably don't need a spinlock around this, but
FYI: I've posted the above to the linux-serial mailing list but have not
received any additional feedback after reworking to incorporate changes
recommended via that mailing list. That thread ends here:
http://www.spinics.net/lists/linux-serial/msg00196.html
I'm now posting this reworked version to linux-kernel to move this along.
TIA for comments/feedback!
--
Regards,
George
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