i2c-piix4: Support AMD auxiliary SMBus controller

Some AMD chipsets, such as the SP5100, have an auxiliary SMBus
controller with a second set of registers. This patch adds
support for this auxiliary controller.

Tested on ASUS KCMA-D8 motherboard.

Signed-off-by: Andrew Armenia <andrew@asquaredlabs.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/i2c/busses/i2c-piix4 b/Documentation/i2c/busses/i2c-piix4
index 475bb4ae0720..1e6634f54c50 100644
--- a/Documentation/i2c/busses/i2c-piix4
+++ b/Documentation/i2c/busses/i2c-piix4
@@ -8,6 +8,11 @@ Supported adapters:
     Datasheet: Only available via NDA from ServerWorks
   * ATI IXP200, IXP300, IXP400, SB600, SB700 and SB800 southbridges
     Datasheet: Not publicly available
+    SB700 register reference available at:
+    http://support.amd.com/us/Embedded_TechDocs/43009_sb7xx_rrg_pub_1.00.pdf
+  * AMD SP5100 (SB700 derivative found on some server mainboards)
+    Datasheet: Publicly available at the AMD website
+    http://support.amd.com/us/Embedded_TechDocs/44413.pdf
   * AMD Hudson-2
     Datasheet: Not publicly available
   * Standard Microsystems (SMSC) SLC90E66 (Victory66) southbridge
@@ -68,6 +73,10 @@ this driver on those mainboards.
 The ServerWorks Southbridges, the Intel 440MX, and the Victory66 are
 identical to the PIIX4 in I2C/SMBus support.
 
+The AMD SB700 and SP5100 chipsets implement two PIIX4-compatible SMBus
+controllers. If your BIOS initializes the secondary controller, it will
+be detected by this driver as an "Auxiliary SMBus Host Controller".
+
 If you own Force CPCI735 motherboard or other OSB4 based systems you may need
 to change the SMBus Interrupt Select register so the SMBus controller uses
 the SMI mode.