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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Guenter Roeck <linux@roeck-us.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.4 19/25] hwmon: (lm90) Reduce maximum conversion rate for G781
Date:   Tue,  1 Feb 2022 19:16:43 +0100
Message-Id: <20220201180822.768065388@linuxfoundation.org>
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From: Guenter Roeck <linux@roeck-us.net>

[ Upstream commit a66c5ed539277b9f2363bbace0dba88b85b36c26 ]

According to its datasheet, G781 supports a maximum conversion rate value
of 8 (62.5 ms). However, chips labeled G781 and G780 were found to only
support a maximum conversion rate value of 7 (125 ms). On the other side,
chips labeled G781-1 and G784 were found to support a conversion rate value
of 8. There is no known means to distinguish G780 from G781 or G784; all
chips report the same manufacturer ID and chip revision.
Setting the conversion rate register value to 8 on chips not supporting
it causes unexpected behavior since the real conversion rate is set to 0
(16 seconds) if a value of 8 is written into the conversion rate register.
Limit the conversion rate register value to 7 for all G78x chips to avoid
the problem.

Fixes: ae544f64cc7b ("hwmon: (lm90) Add support for GMT G781")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/hwmon/lm90.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
index 420f341272621..6f6f173aca6f2 100644
--- a/drivers/hwmon/lm90.c
+++ b/drivers/hwmon/lm90.c
@@ -265,7 +265,7 @@ static const struct lm90_params lm90_params[] = {
 		.flags = LM90_HAVE_OFFSET | LM90_HAVE_REM_LIMIT_EXT
 		  | LM90_HAVE_BROKEN_ALERT,
 		.alert_alarms = 0x7c,
-		.max_convrate = 8,
+		.max_convrate = 7,
 	},
 	[lm86] = {
 		.flags = LM90_HAVE_OFFSET | LM90_HAVE_REM_LIMIT_EXT,
-- 
2.34.1