linux-kernel - [PATCH] serial: 8250: omap: Provide ability to enable/disable UART as wakeup source

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Date:   Tue, 27 Mar 2018 17:32:17 +0530
From:   Vignesh R <vigneshr@...com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Jiri Slaby <jslaby@...e.com>, Tony Lindgren <tony@...mide.com>,
        Vignesh R <vigneshr@...com>, <linux-serial@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>
Subject: [PATCH] serial: 8250: omap: Provide ability to enable/disable UART as wakeup source

Enable/Clear module level UART wakeup in UART_OMAP_WER register based on
return value of device_may_wakeup() in .suspend(). This allows
userspace to use sysfs to control the ability of UART to wakeup the
system from deep sleep state. Register is restored back in .startup()
call that happens as part of resume sequence.

With this patch, userspace can control UART wakeup capability via sysfs:
To enable wakeup capability:
echo enabled >  /sys/class/tty/ttyXX/device/power/wakeup
For disabling wakeup capability:
echo disabled > /sys/class/tty/ttyXX/device/power/wakeup

Signed-off-by: Vignesh R <vigneshr@...com>
---
 drivers/tty/serial/8250/8250_omap.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 624b501fd253..6aaa84355fd1 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -1310,8 +1310,17 @@ static void omap8250_complete(struct device *dev)
 static int omap8250_suspend(struct device *dev)
 {
 	struct omap8250_priv *priv = dev_get_drvdata(dev);
+	struct uart_8250_port *up = serial8250_get_port(priv->line);
 
 	serial8250_suspend_port(priv->line);
+
+	pm_runtime_get_sync(dev);
+	if (!device_may_wakeup(dev))
+		priv->wer = 0;
+	serial_out(up, UART_OMAP_WER, priv->wer);
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_autosuspend(dev);
+
 	flush_work(&priv->qos_work);
 	return 0;
 }
@@ -1403,6 +1412,8 @@ static int omap8250_runtime_suspend(struct device *dev)
 
 		/* Restore to UART mode after reset (for wakeup) */
 		omap8250_update_mdr1(up, priv);
+		/* Restore wakeup enable register */
+		serial_out(up, UART_OMAP_WER, priv->wer);
 	}
 
 	if (up->dma && up->dma->rxchan)
-- 
2.16.2