hwmon: (lm90) Reduce maximum conversion rate for G781

BugLink: https://bugs.launchpad.net/bugs/1959879
[ 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>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
index d435954782ed8a027e81fe2b29264756278ec33e..12a8af36c201b9228ca345690c8bff2ac2ef9b23 100644 (file)
--- a/drivers/hwmon/lm90.c
+++ b/drivers/hwmon/lm90.c
@@ -373,7 +373,7 @@ static const struct lm90_params lm90_params[] = {
                .flags = LM90_HAVE_OFFSET | LM90_HAVE_REM_LIMIT_EXT
                  | LM90_HAVE_BROKEN_ALERT | LM90_HAVE_CRIT,
                .alert_alarms = 0x7c,
-               .max_convrate = 8,
+               .max_convrate = 7,
        },
        [lm86] = {
                .flags = LM90_HAVE_OFFSET | LM90_HAVE_REM_LIMIT_EXT