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authorJean Delvare <khali@linux-fr.org>2013-05-04 16:49:36 +0400
committerJean Delvare <khali@endymion.delvare>2013-05-04 16:49:36 +0400
commit0cd2c72d765191f24d7be14366c0413bf139f3e3 (patch)
tree77d19cabe37cd11b6c5c5f14e8e5dc05da81802f /Documentation
parent87d0621ae2bdf2e2c60aadbbcb8b6c680777c1bf (diff)
downloadlinux-0cd2c72d765191f24d7be14366c0413bf139f3e3.tar.xz
hwmon: (lm75) Tune resolution and sample time per chip
Most LM75-compatible chips can either sample much faster or with a much better resolution than the original LM75 chip. So far the lm75 driver did not let the user take benefit of these improvements. Do it now. I decided to almost always configure the chip to use the best resolution possible, which also means the longest sample time. The only chips for which I didn't are the DS75, DS1775 and STDS75, because they are really too slow in 12-bit mode (1.2 to 1.5 second worst case) so I went for 11-bit mode as a more reasonable tradeoff. This choice is dictated by the fact that the hwmon subsystem is meant for system monitoring, it has never been supposed to be ultra-fast, and as a matter of fact we do cache the sampled values in almost all drivers. If anyone isn't pleased with these default settings, they can always introduce a platform data structure or DT support for the lm75. That being said, it seems nobody ever complained that the driver wouldn't refresh the value faster than every 1.5 second, and the change made it faster for all chips even in 12-bit mode, so I don't expect any complaint. Signed-off-by: Jean Delvare <khali@linux-fr.org> Acked-by: Guenter Roeck <linux@roeck-us.net>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/hwmon/lm757
1 files changed, 4 insertions, 3 deletions
diff --git a/Documentation/hwmon/lm75 b/Documentation/hwmon/lm75
index 69af1c7db6b7..5e45d0795986 100644
--- a/Documentation/hwmon/lm75
+++ b/Documentation/hwmon/lm75
@@ -67,7 +67,8 @@ the temperature falls below the Hysteresis value.
All temperatures are in degrees Celsius, and are guaranteed within a
range of -55 to +125 degrees.
-The LM75 only updates its values each 1.5 seconds; reading it more often
+The driver caches the values for a period varying between 1 second for the
+slowest chips and 125 ms for the fastest chips; reading it more often
will do no harm, but will return 'old' values.
The original LM75 was typically used in combination with LM78-like chips
@@ -78,8 +79,8 @@ The LM75 is essentially an industry standard; there may be other
LM75 clones not listed here, with or without various enhancements,
that are supported. The clones are not detected by the driver, unless
they reproduce the exact register tricks of the original LM75, and must
-therefore be instantiated explicitly. The specific enhancements (such as
-higher resolution) are not currently supported by the driver.
+therefore be instantiated explicitly. Higher resolution up to 12-bit
+is supported by this driver, other specific enhancements are not.
The LM77 is not supported, contrary to what we pretended for a long time.
Both chips are simply not compatible, value encoding differs.