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[PATCH] serial: make sure UART is powered up when dumping MCTRL status

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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@mvista.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
George G. Davis 2007-02-14 00:33:06 -08:00 committed by Linus Torvalds
parent 9b22271d4b
commit 3689a0ec60
1 changed files with 11 additions and 0 deletions
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11
drivers/serial/serial_core.c
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@ -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) static int uart_line_info(char *buf, struct uart_driver *drv, int i)
{ {
struct uart_state *state = drv->state + i; struct uart_state *state = drv->state + i;
int pm_state;
struct uart_port *port = state->port; struct uart_port *port = state->port;
char stat_buf[32]; char stat_buf[32];
unsigned int status; 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)) 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); spin_lock_irq(&port->lock);
status = port->ops->get_mctrl(port); status = port->ops->get_mctrl(port);
spin_unlock_irq(&port->lock); 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", ret += sprintf(buf + ret, " tx:%d rx:%d",
port->icount.tx, port->icount.rx); 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); 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. * Ensure that the modem control lines are de-activated.
* We probably don't need a spinlock around this, but * We probably don't need a spinlock around this, but