[PATCH] serial: make sure UART is powered up when dumping MCTRL status (3689a0ec) · Commits · 戴 / test

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>

drivers/serial/serial_core.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -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

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