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From: Mariusz Bialonczyk <manio@skyboo.net>
To: linux-kernel@vger.kernel.org, Greg Kroah-Hartman <greg@kroah.com>
Cc: Mariusz Bialonczyk <manio@skyboo.net>
Subject: [PATCH 3/4] w1: ds2413: when the slave is not responding during read, select it again
Date: Mon, 20 May 2019 09:05:57 +0200	[thread overview]
Message-ID: <20190520070558.20142-3-manio@skyboo.net> (raw)
In-Reply-To: <20190520070558.20142-1-manio@skyboo.net>

The protocol is not allowing to obtain a byte of 0xff for PIO_ACCESS_READ
call. It is very likely that the slave was not addressed properly and
it is just not respoding (leaving the bus in logic high state) during
the read of sampled PIO value.
We cannot just call w1_reset_resume_command() because the problem will
persist, instead try selecting (addressing) the slave again.

Signed-off-by: Mariusz Bialonczyk <manio@skyboo.net>
---
 drivers/w1/slaves/w1_ds2413.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/w1/slaves/w1_ds2413.c b/drivers/w1/slaves/w1_ds2413.c
index d63778c70568..1854461d4d56 100644
--- a/drivers/w1/slaves/w1_ds2413.c
+++ b/drivers/w1/slaves/w1_ds2413.c
@@ -24,6 +24,7 @@
 #define W1_F3A_FUNC_PIO_ACCESS_READ        0xF5
 #define W1_F3A_FUNC_PIO_ACCESS_WRITE       0x5A
 #define W1_F3A_SUCCESS_CONFIRM_BYTE        0xAA
+#define W1_F3A_INVALID_PIO_STATE           0xFF
 
 static ssize_t state_read(struct file *filp, struct kobject *kobj,
 			  struct bin_attribute *bin_attr, char *buf, loff_t off,
@@ -45,6 +46,7 @@ static ssize_t state_read(struct file *filp, struct kobject *kobj,
 	mutex_lock(&sl->master->bus_mutex);
 	dev_dbg(&sl->dev, "mutex locked");
 
+next:
 	if (w1_reset_select_slave(sl))
 		goto out;
 
@@ -52,8 +54,13 @@ static ssize_t state_read(struct file *filp, struct kobject *kobj,
 		w1_write_8(sl->master, W1_F3A_FUNC_PIO_ACCESS_READ);
 
 		*buf = w1_read_8(sl->master);
-		/* check for correct complement */
-		if ((*buf & 0x0F) == ((~*buf >> 4) & 0x0F)) {
+		if (*buf == W1_F3A_INVALID_PIO_STATE) {
+			/* slave didn't respond, try to select it again */
+			dev_warn(&sl->dev, "slave device did not respond to PIO_ACCESS_READ, " \
+					    "reselecting, retries left: %d\n", retries);
+			goto next;
+		} else if ((*buf & 0x0F) == ((~*buf >> 4) & 0x0F)) {
+			/* complement is correct */
 			bytes_read = 1;
 			goto out;
 		}
-- 
2.19.0.rc1


  parent reply	other threads:[~2019-05-20  7:06 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20  7:05 [PATCH 1/4] w1: ds2413: output_write() cosmetic fixes / simplify Mariusz Bialonczyk
2019-05-20  7:05 ` [PATCH 2/4] w1: ds2413: add retry support to state_read() Mariusz Bialonczyk
2019-05-20  7:05 ` Mariusz Bialonczyk [this message]
2019-05-22 10:40   ` [PATCH 3/4 v2] w1: ds2413: when the slave is not responding during read, select it again Mariusz Bialonczyk
2019-05-20  7:05 ` [PATCH 4/4] w1: ds2805: rename w1_family struct, fixing c-p typo Mariusz Bialonczyk
2019-05-24 18:21   ` Greg KH
2019-05-25  8:45     ` [PATCH 4/4 v2] " Mariusz Bialonczyk
2019-05-25  8:51     ` [PATCH 4/4] " Mariusz Bialonczyk

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