serial: omap: stick to put_autosuspend

Everytime we're done using our TTY, we want
the pm timer to be reinitilized. By sticking
to pm_runtime_pm_autosuspend() we make sure
that this will always be the case.

The idea behind this patch is to make sure we
will always reinitialize the pm timer so that
we don't fall into a situation where pm_runtime_put()
expires right away (if timer was already about to
expire when we made the call to pm_runtime_put()).

While suspending right away wouldn't cause any
issues, reinitializing the pm timer can help us
avoiding unnecessary context save & restore
operations (which are somewhat expensive) if there's
another read/write/set_termios request coming right
after. IOW, we are trying to make sure UART is still
powered up while it's still under heavy usage.
Tested-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/omap-serial.c

@@ -165,7 +165,8 @@ static void serial_omap_enable_ms(struct uart_port *port)
 	pm_runtime_get_sync(up->dev);
 	up->ier |= UART_IER_MSI;
 	serial_out(up, UART_IER, up->ier);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 }
 
 static void serial_omap_stop_tx(struct uart_port *port)
@@ -415,7 +416,8 @@ static unsigned int serial_omap_tx_empty(struct uart_port *port)
 	spin_lock_irqsave(&up->port.lock, flags);
 	ret = serial_in(up, UART_LSR) & UART_LSR_TEMT ? TIOCSER_TEMT : 0;
 	spin_unlock_irqrestore(&up->port.lock, flags);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 	return ret;
 }
 
@@ -427,7 +429,8 @@ static unsigned int serial_omap_get_mctrl(struct uart_port *port)
 
 	pm_runtime_get_sync(up->dev);
 	status = check_modem_status(up);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 
 	dev_dbg(up->port.dev, "serial_omap_get_mctrl+%d\n", up->port.line);
 
@@ -463,7 +466,8 @@ static void serial_omap_set_mctrl(struct uart_port *port, unsigned int mctrl)
 	up->mcr = serial_in(up, UART_MCR);
 	up->mcr |= mcr;
 	serial_out(up, UART_MCR, up->mcr);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 
 	if (gpio_is_valid(up->DTR_gpio) &&
 	    !!(mctrl & TIOCM_DTR) != up->DTR_active) {
@@ -490,7 +494,8 @@ static void serial_omap_break_ctl(struct uart_port *port, int break_state)
 		up->lcr &= ~UART_LCR_SBC;
 	serial_out(up, UART_LCR, up->lcr);
 	spin_unlock_irqrestore(&up->port.lock, flags);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 }
 
 static int serial_omap_startup(struct uart_port *port)
@@ -588,7 +593,8 @@ static void serial_omap_shutdown(struct uart_port *port)
 	if (serial_in(up, UART_LSR) & UART_LSR_DR)
 		(void) serial_in(up, UART_RX);
 
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 	free_irq(up->port.irq, up);
 }
 
@@ -862,7 +868,8 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
 	serial_omap_configure_xonxoff(up, termios);
 
 	spin_unlock_irqrestore(&up->port.lock, flags);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 	dev_dbg(up->port.dev, "serial_omap_set_termios+%d\n", up->port.line);
 }
 
@@ -893,7 +900,8 @@ serial_omap_pm(struct uart_port *port, unsigned int state,
 			pm_runtime_allow(up->dev);
 	}
 
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 }
 
 static void serial_omap_release_port(struct uart_port *port)
@@ -975,7 +983,8 @@ static void serial_omap_poll_put_char(struct uart_port *port, unsigned char ch)
 	pm_runtime_get_sync(up->dev);
 	wait_for_xmitr(up);
 	serial_out(up, UART_TX, ch);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 }
 
 static int serial_omap_poll_get_char(struct uart_port *port)
@@ -989,7 +998,8 @@ static int serial_omap_poll_get_char(struct uart_port *port)
 		return NO_POLL_CHAR;
 
 	status = serial_in(up, UART_RX);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 	return status;
 }
 
@@ -1340,7 +1350,8 @@ static int serial_omap_probe(struct platform_device *pdev)
 	if (ret != 0)
 		goto err_add_port;
 
-	pm_runtime_put(&pdev->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 	platform_set_drvdata(pdev, up);
 	return 0;