3 files changed, 67 insertions, 12 deletions

diff --git a/Documentation/hwmon/it87 b/Documentation/hwmon/it87
index 74a80992d237..c0528d6f9ace 100644
--- a/Documentation/hwmon/it87
+++ b/Documentation/hwmon/it87
@@ -135,6 +135,16 @@ Give 0 for unused sensor. Any other value is invalid. To configure this at
 startup, consult lm_sensors's /etc/sensors.conf. (2 = thermistor;
 3 = thermal diode)
 
+
+Fan speed control
+-----------------
+
 The fan speed control features are limited to manual PWM mode. Automatic
 "Smart Guardian" mode control handling is not implemented. However
 if you want to go for "manual mode" just write 1 to pwmN_enable.
+
+If you are only able to control the fan speed with very small PWM values,
+try lowering the PWM base frequency (pwm1_freq). Depending on the fan,
+it may give you a somewhat greater control range. The same frequency is
+used to drive all fan outputs, which is why pwm2_freq and pwm3_freq are
+read-only.
diff --git a/Documentation/hwmon/sysfs-interface b/Documentation/hwmon/sysfs-interface
index efef3b962cd3..d73d2e8c7534 100644
--- a/Documentation/hwmon/sysfs-interface
+++ b/Documentation/hwmon/sysfs-interface
@@ -166,16 +166,21 @@ pwm[1-*]	Pulse width modulation fan control.
 
 pwm[1-*]_enable
                 Switch PWM on and off.
-                Not always present even if fan*_pwm is.
+                Not always present even if pwmN is.
                 0: turn off
                 1: turn on in manual mode
                 2+: turn on in automatic mode
-                Check individual chip documentation files for automatic mode details.
+                Check individual chip documentation files for automatic mode
+                details.
                 RW
 
-pwm[1-*]_mode
-                0: DC mode
-                1: PWM mode
+pwm[1-*]_mode   0: DC mode (direct current)
+                1: PWM mode (pulse-width modulation)
+                RW
+
+pwm[1-*]_freq   Base PWM frequency in Hz.
+                Only possibly available when pwmN_mode is PWM, but not always
+                present even then.
                 RW
 
 pwm[1-*]_auto_channels_temp
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.