linux-kernel - [PATCH] w1: w1_therm: fixes w1

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Date:   Wed, 23 Feb 2022 11:35:55 +0000
From:   Lucas Denefle <lucas.denefle@...verge.io>
To:     zbr@...emap.net, lucas.denefle@...verge.io
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Yang Yingliang <yangyingliang@...wei.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Bhaskar Chowdhury <unixbhaskar@...il.com>,
        Yang Guang <yang.guang5@....com.cn>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] w1: w1_therm: fixes w1_seq for ds28ea00 sensors

w1_seq was failing due to several devices responding to the
CHAIN_DONE at the same time. Now properly selects the current
device in the chain with MATCH_ROM. Also acknowledgment was
read twice.

Signed-off-by: Lucas Denefle <lucas.denefle@...verge.io>
---
 drivers/w1/slaves/w1_therm.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index 565578002d79..c7b8a8e787e2 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -2089,16 +2089,20 @@ static ssize_t w1_seq_show(struct device *device,
 		if (sl->reg_num.id == reg_num->id)
 			seq = i;
 
+		if (w1_reset_bus(sl->master))
+			goto error;
+
+		/* Put the device into chain DONE state */
+		w1_write_8(sl->master, W1_MATCH_ROM);
+		w1_write_block(sl->master, (u8 *)&rn, 8);
 		w1_write_8(sl->master, W1_42_CHAIN);
 		w1_write_8(sl->master, W1_42_CHAIN_DONE);
 		w1_write_8(sl->master, W1_42_CHAIN_DONE_INV);
-		w1_read_block(sl->master, &ack, sizeof(ack));
 
 		/* check for acknowledgment */
 		ack = w1_read_8(sl->master);
 		if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
 			goto error;
-
 	}
 
 	/* Exit from CHAIN state */
-- 
2.35.1