hwmon: (lm90) Reduce maximum conversion rate for G781

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: ae544f6 ("hwmon: (lm90) Add support for GMT G781")
Signed-off-by: Guenter Roeck <[email protected]>

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