Greetings, 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 <gdavis@xxxxxxxxxx> --- drivers/serial/serial_core.c | 12 ++++++++++++ 1 files changed, 12 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); @@ -2068,6 +2076,10 @@ uart_configure_port(struct uart_driver * uart_report_port(drv, port); + /* Power up port for set_mctrl() */ + if (!uart_console(port)) + uart_change_pm(state, 0); + /* * Ensure that the modem control lines are de-activated. * We probably don't need a spinlock around this, but Comments appreciated. TIA! -- Regards, George - To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html