1 files changed, 47 insertions, 7 deletions

diff --git a/Documentation/hwmon/w83627ehf b/Documentation/hwmon/w83627ehf
index 8a15a7408753..030fac6cec7a 100644
--- a/Documentation/hwmon/w83627ehf
+++ b/Documentation/hwmon/w83627ehf
@@ -2,26 +2,29 @@ Kernel driver w83627ehf
 =======================
 
 Supported chips:
-  * Winbond W83627EHF/EHG (ISA access ONLY)
+  * Winbond W83627EHF/EHG/DHG (ISA access ONLY)
     Prefix: 'w83627ehf'
     Addresses scanned: ISA address retrieved from Super I/O registers
-    Datasheet: http://www.winbond-usa.com/products/winbond_products/pdfs/PCIC/W83627EHF_%20W83627EHGb.pdf
+    Datasheet:
+        http://www.winbond-usa.com/products/winbond_products/pdfs/PCIC/W83627EHF_%20W83627EHGb.pdf
+        DHG datasheet confidential.
 
 Authors:
         Jean Delvare <khali@linux-fr.org>
         Yuan Mu (Winbond)
         Rudolf Marek <r.marek@assembler.cz>
+        David Hubbard <david.c.hubbard@gmail.com>
 
 Description
 -----------
 
-This driver implements support for the Winbond W83627EHF and W83627EHG
-super I/O chips. We will refer to them collectively as Winbond chips.
+This driver implements support for the Winbond W83627EHF, W83627EHG, and
+W83627DHG super I/O chips. We will refer to them collectively as Winbond chips.
 
 The chips implement three temperature sensors, five fan rotation
-speed sensors, ten analog voltage sensors, alarms with beep warnings (control
-unimplemented), and some automatic fan regulation strategies (plus manual
-fan control mode).
+speed sensors, ten analog voltage sensors (only nine for the 627DHG), alarms
+with beep warnings (control unimplemented), and some automatic fan regulation
+strategies (plus manual fan control mode).
 
 Temperatures are measured in degrees Celsius and measurement resolution is 1
 degC for temp1 and 0.5 degC for temp2 and temp3. An alarm is triggered when
@@ -55,6 +58,9 @@ prog  -> pwm4 (the programmable setting is not supported by the driver)
 /sys files
 ----------
 
+name - this is a standard hwmon device entry. For the W83627EHF and W83627EHG,
+       it is set to "w83627ehf" and for the W83627DHG it is set to "w83627dhg"
+
 pwm[1-4] - this file stores PWM duty cycle or DC value (fan speed) in range:
            0 (stop) to 255 (full)
 
@@ -83,3 +89,37 @@ pwm[1-4]_stop_time  - how many milliseconds [ms] must elapse to switch
 
 Note: last two functions are influenced by other control bits, not yet exported
       by the driver, so a change might not have any effect.
+
+Implementation Details
+----------------------
+
+Future driver development should bear in mind that the following registers have
+different functions on the 627EHF and the 627DHG. Some registers also have
+different power-on default values, but BIOS should already be loading
+appropriate defaults. Note that bank selection must be performed as is currently
+done in the driver for all register addresses.
+
+0x49:  only on DHG, selects temperature source for AUX fan, CPU fan0
+0x4a:  not completely documented for the EHF and the DHG documentation assigns
+       different behavior to bits 7 and 6, including extending the temperature
+       input selection to SmartFan I, not just SmartFan III. Testing on the EHF
+       will reveal whether they are compatible or not.
+
+0x58:  Chip ID: 0xa1=EHF 0xc1=DHG
+0x5e:  only on DHG, has bits to enable "current mode" temperature detection and
+       critical temperature protection
+0x45b: only on EHF, bit 3, vin4 alarm (EHF supports 10 inputs, only 9 on DHG)
+0x552: only on EHF, vin4
+0x558: only on EHF, vin4 high limit
+0x559: only on EHF, vin4 low limit
+0x6b:  only on DHG, SYS fan critical temperature
+0x6c:  only on DHG, CPU fan0 critical temperature
+0x6d:  only on DHG, AUX fan critical temperature
+0x6e:  only on DHG, CPU fan1 critical temperature
+
+0x50-0x55 and 0x650-0x657 are marked "Test Register" for the EHF, but "Reserved
+       Register" for the DHG
+
+The DHG also supports PECI, where the DHG queries Intel CPU temperatures, and
+the ICH8 southbridge gets that data via PECI from the DHG, so that the
+southbridge drives the fans. And the DHG supports SST, a one-wire serial bus.