From: George G. Davis Date: Wed, 14 Feb 2007 08:33:06 +0000 (-0800) Subject: [PATCH] serial: make sure UART is powered up when dumping MCTRL status X-Git-Tag: firefly_0821_release~31290 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=3689a0ec60bc8f56cc372c1dfa0d89dab48f7c9c;p=firefly-linux-kernel-4.4.55.git [PATCH] serial: make sure UART is powered up when dumping MCTRL status 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 Cc: Russell King Cc: Alan Cox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c index f84982e508c7..66fdd3b2b958 100644 --- a/drivers/serial/serial_core.c +++ b/drivers/serial/serial_core.c @@ -1660,6 +1660,7 @@ static const char *uart_type(struct uart_port *port) 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; @@ -1682,9 +1683,16 @@ static int uart_line_info(char *buf, struct uart_driver *drv, int i) 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); @@ -2100,6 +2108,9 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state, 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