openwrt/target/linux/bcm27xx/patches-4.19/950-0589-w1-ds2413-add-retry-support-to-state_read.patch

From 91e443597cdd8f89d2b68ea5bf0f0823d1853ab7 Mon Sep 17 00:00:00 2001
From: Mariusz Bialonczyk <manio@skyboo.net>
Date: Mon, 20 May 2019 09:05:56 +0200
Subject: [PATCH] w1: ds2413: add retry support to state_read()

commit c50d09a86172073f55ebac0b92ad5a75907d64e7 upstream.

The state_read() was calling PIO_ACCESS_READ once and bail out if it
failed for this first time.
This commit is improving this to trying more times before it give up,
similarly as the write call is currently doing.

Signed-off-by: Mariusz Bialonczyk <manio@skyboo.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/w1/slaves/w1_ds2413.c | 37 +++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 13 deletions(-)

--- a/drivers/w1/slaves/w1_ds2413.c
+++ b/drivers/w1/slaves/w1_ds2413.c
@@ -30,6 +30,9 @@ static ssize_t state_read(struct file *f
 			  size_t count)
 {
 	struct w1_slave *sl = kobj_to_w1_slave(kobj);
+	unsigned int retries = W1_F3A_RETRIES;
+	ssize_t bytes_read = -EIO;
+
 	dev_dbg(&sl->dev,
 		"Reading %s kobj: %p, off: %0#10x, count: %zu, buff addr: %p",
 		bin_attr->attr.name, kobj, (unsigned int)off, count, buf);
@@ -42,22 +45,30 @@ static ssize_t state_read(struct file *f
 	mutex_lock(&sl->master->bus_mutex);
 	dev_dbg(&sl->dev, "mutex locked");
 
-	if (w1_reset_select_slave(sl)) {
-		mutex_unlock(&sl->master->bus_mutex);
-		return -EIO;
-	}
+	if (w1_reset_select_slave(sl))
+		goto out;
 
-	w1_write_8(sl->master, W1_F3A_FUNC_PIO_ACCESS_READ);
-	*buf = w1_read_8(sl->master);
+	while (retries--) {
+		w1_write_8(sl->master, W1_F3A_FUNC_PIO_ACCESS_READ);
 
-	mutex_unlock(&sl->master->bus_mutex);
-	dev_dbg(&sl->dev, "mutex unlocked");
+		*buf = w1_read_8(sl->master);
+		/* check for correct complement */
+		if ((*buf & 0x0F) == ((~*buf >> 4) & 0x0F)) {
+			bytes_read = 1;
+			goto out;
+		}
+
+		if (w1_reset_resume_command(sl->master))
+			goto out; /* unrecoverable error */
 
-	/* check for correct complement */
-	if ((*buf & 0x0F) != ((~*buf >> 4) & 0x0F))
-		return -EIO;
-	else
-		return 1;
+		dev_warn(&sl->dev, "PIO_ACCESS_READ error, retries left: %d\n", retries);
+	}
+
+out:
+	mutex_unlock(&sl->master->bus_mutex);
+	dev_dbg(&sl->dev, "%s, mutex unlocked, retries: %d\n",
+		(bytes_read > 0) ? "succeeded" : "error", retries);
+	return bytes_read;
 }
 
 static BIN_ATTR_RO(state, 1);