From 9479d8f12efc845faca4bb1aef9b6e63799a7e5c Mon Sep 17 00:00:00 2001
From: "Arun P. Mohanan" <arun.p.m@linux.intel.com>
Date: Wed, 18 Mar 2020 08:34:43 +0530
Subject: [PATCH] Add poll fops in eSPI driver

Modify eSPI driver to support poll fops.

Signed-off-by: Arun P. Mohanan <arun.p.m@linux.intel.com>
---
 drivers/misc/aspeed-espi-slave.c | 85 +++++++++++++++++++++++---------
 1 file changed, 61 insertions(+), 24 deletions(-)

diff --git a/drivers/misc/aspeed-espi-slave.c b/drivers/misc/aspeed-espi-slave.c
index 87bc81948694..cb8ed585c69f 100644
--- a/drivers/misc/aspeed-espi-slave.c
+++ b/drivers/misc/aspeed-espi-slave.c
@@ -9,6 +9,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/poll.h>
 #include <linux/regmap.h>
 #include <linux/reset.h>
 #include <linux/sched/signal.h>
@@ -95,6 +96,7 @@ struct aspeed_espi {
 	spinlock_t		pltrstn_lock; /* for PLTRST_N signal sampling */
 	wait_queue_head_t	pltrstn_waitq;
 	char			pltrstn;
+	bool			pltrstn_in_avail;
 };
 
 static void aspeed_espi_sys_event(struct aspeed_espi *priv)
@@ -127,7 +129,10 @@ static void aspeed_espi_sys_event(struct aspeed_espi *priv)
 		dev_dbg(priv->dev, "SYSEVT_OOB_RST_WARN: acked\n");
 	}
 	if (sts & ASPEED_ESPI_SYSEVT_PLTRSTN || priv->pltrstn == 'U') {
+		spin_lock(&priv->pltrstn_lock);
 		priv->pltrstn = (evt & ASPEED_ESPI_SYSEVT_PLTRSTN) ? '1' : '0';
+		priv->pltrstn_in_avail = true;
+		spin_unlock(&priv->pltrstn_lock);
 		wake_up_interruptible(&priv->pltrstn_waitq);
 		dev_dbg(priv->dev, "SYSEVT_PLTRSTN: %c\n", priv->pltrstn);
 	}
@@ -269,6 +274,8 @@ static int aspeed_espi_pltrstn_open(struct inode *inode, struct file *filp)
 {
 	if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 		return -EACCES;
+	struct aspeed_espi *priv = to_aspeed_espi(filp);
+	priv->pltrstn_in_avail = true ; /*Setting true returns first data after file open*/
 
 	return 0;
 }
@@ -284,41 +291,71 @@ static ssize_t aspeed_espi_pltrstn_read(struct file *filp, char __user *buf,
 
 	spin_lock_irqsave(&priv->pltrstn_lock, flags);
 
-	add_wait_queue(&priv->pltrstn_waitq, &wait);
-	set_current_state(TASK_INTERRUPTIBLE);
-
-	old_sample = priv->pltrstn;
-
-	do {
-		char new_sample = priv->pltrstn;
-
-		if (filp->f_flags & O_NONBLOCK || old_sample != new_sample) {
-			ret = put_user(new_sample, (unsigned long __user *)buf);
-			if (!ret)
-				ret = sizeof(new_sample);
-		} else if (signal_pending(current)) {
-			ret = -ERESTARTSYS;
+	if (filp->f_flags & O_NONBLOCK) {
+		if (!priv->pltrstn_in_avail) {
+			ret = -EAGAIN;
+			goto out_unlock;
 		}
-
-		if (!ret) {
-			spin_unlock_irqrestore(&priv->pltrstn_lock, flags);
-			schedule();
-			spin_lock_irqsave(&priv->pltrstn_lock, flags);
+		char data = priv->pltrstn;
+		ret = put_user(data, (unsigned long __user *)buf);
+		if (!ret){
+			ret = sizeof(data);
+		} else{
+			ret = -EAGAIN;
 		}
-	} while (!ret);
-
-	remove_wait_queue(&priv->pltrstn_waitq, &wait);
-	set_current_state(TASK_RUNNING);
-
+		priv->pltrstn_in_avail = false;
+	} else {
+		add_wait_queue(&priv->pltrstn_waitq, &wait);
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		old_sample = priv->pltrstn;
+
+		do {
+			char new_sample = priv->pltrstn;
+
+			if (old_sample != new_sample) {
+				ret = put_user(new_sample,
+						 (unsigned long __user *)buf);
+				if (!ret)
+					ret = sizeof(new_sample);
+			} else if (signal_pending(current)) {
+				ret = -ERESTARTSYS;
+			}
+
+			if (!ret) {
+				spin_unlock_irqrestore(&priv->pltrstn_lock,
+							 flags);
+				schedule();
+				spin_lock_irqsave(&priv->pltrstn_lock, flags);
+			}
+		} while (!ret);
+
+		remove_wait_queue(&priv->pltrstn_waitq, &wait);
+		set_current_state(TASK_RUNNING);
+	}
+out_unlock:
 	spin_unlock_irqrestore(&priv->pltrstn_lock, flags);
 
 	return ret;
 }
 
+static unsigned int aspeed_espi_pltrstn_poll(struct file *file,
+						 poll_table *wait)
+{
+	struct aspeed_espi *priv = to_aspeed_espi(file);
+	unsigned int mask = 0;
+	poll_wait(file, &priv->pltrstn_waitq, wait);
+
+	if (priv->pltrstn_in_avail)
+		mask |= POLLIN;
+	return mask;
+}
+
 static const struct file_operations aspeed_espi_pltrstn_fops = {
 	.owner	= THIS_MODULE,
 	.open	= aspeed_espi_pltrstn_open,
 	.read	= aspeed_espi_pltrstn_read,
+	.poll	= aspeed_espi_pltrstn_poll,
 };
 
 static const struct regmap_config aspeed_espi_regmap_cfg = {
-- 
2.17.1