hwmon: (adm1021) Clarify documentation regarding Xeon processors

Recent Xeon processor thermal sensors are supported by the coretemp
driver and not the adm1021 driver. Only one old generation of Xeon
processors (the first Netburst ones) are supported by the adm1021
driver.

Reported-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>

1 files changed, 19 insertions, 17 deletions

diff --git a/Documentation/hwmon/adm1021 b/Documentation/hwmon/adm1021
index 03d02bfb3df1..02ad96cf9b2b 100644
--- a/Documentation/hwmon/adm1021
+++ b/Documentation/hwmon/adm1021
@@ -14,10 +14,6 @@ Supported chips:
     Prefix: 'gl523sm'
     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
     Datasheet:
-  * Intel Xeon Processor
-    Prefix: - any other - may require 'force_adm1021' parameter
-    Addresses scanned: none
-    Datasheet: Publicly available at Intel website
   * Maxim MAX1617
     Prefix: 'max1617'
     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
@@ -91,21 +87,27 @@ will do no harm, but will return 'old' values. It is possible to make
 ADM1021-clones do faster measurements, but there is really no good reason
 for that.
 
-Xeon support
-------------
 
-Some Xeon processors have real max1617, adm1021, or compatible chips
-within them, with two temperature sensors.
+Netburst-based Xeon support
+---------------------------
 
-Other Xeons have chips with only one sensor.
+Some Xeon processors based on the Netburst (early Pentium 4, from 2001 to
+2003) microarchitecture had real MAX1617, ADM1021, or compatible chips
+within them, with two temperature sensors. Other Xeon processors of this
+era (with 400 MHz FSB) had chips with only one temperature sensor.
 
-If you have a Xeon, and the adm1021 module loads, and both temperatures
-appear valid, then things are good.
+If you have such an old Xeon, and you get two valid temperatures when
+loading the adm1021 module, then things are good.
 
-If the adm1021 module doesn't load, you should try this:
-        modprobe adm1021 force_adm1021=BUS,ADDRESS
-        ADDRESS can only be 0x18, 0x1a, 0x29, 0x2b, 0x4c, or 0x4e.
+If nothing happens when loading the adm1021 module, and you are certain
+that your specific Xeon processor model includes compatible sensors, you
+will have to explicitly instantiate the sensor chips from user-space. See
+method 4 in Documentation/i2c/instantiating-devices. Possible slave
+addresses are 0x18, 0x1a, 0x29, 0x2b, 0x4c, or 0x4e. It is likely that
+only temp2 will be correct and temp1 will have to be ignored.
 
-If you have dual Xeons you may have appear to have two separate
-adm1021-compatible chips, or two single-temperature sensors, at distinct
-addresses.
+Previous generations of the Xeon processor (based on Pentium II/III)
+didn't have these sensors. Next generations of Xeon processors (533 MHz
+FSB and faster) lost them, until the Core-based generation which
+introduced integrated digital thermal sensors. These are supported by
+the coretemp driver.