Merge tag 'docs-5.4' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "It's a somewhat calmer cycle for docs this time, as the churn of the
  mass RST conversion is happily mostly behind us.

   - A new document on reproducible builds.

   - We finally got around to zapping the documentation for hardware
     support that was removed in 2004; one doesn't want to rush these
     things.

   - The usual assortment of fixes, typo corrections, etc"

* tag 'docs-5.4' of git://git.lwn.net/linux: (67 commits)
  Documentation: kbuild: Add document about reproducible builds
  docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi]
  Documentation: Add "earlycon=sbi" to the admin guide
  doc:lock: remove reference to clever use of read-write lock
  devices.txt: improve entry for comedi (char major 98)
  docs: mtd: Update spi nor reference driver
  doc: arm64: fix grammar dtb placed in no attributes region
  Documentation: sysrq: don't recommend 'S' 'U' before 'B'
  mailmap: Update email address for Quentin Perret
  docs: ftrace: clarify when tracing is disabled by the trace file
  docs: process: fix broken link
  Documentation/arm/samsung-s3c24xx: Remove stray U+FEFF character to fix title
  Documentation/arm/sa1100/assabet: Fix 'make assabet_defconfig' command
  Documentation/arm/sa1100: Remove some obsolete documentation
  docs/zh_CN: update Chinese howto.rst for latexdocs making
  Documentation: virt: Fix broken reference to virt tree's index
  docs: Fix typo on pull requests guide
  kernel-doc: Allow anonymous enum
  Documentation: sphinx: Don't parse socket() as identifier reference
  Documentation: sphinx: Add missing comma to list of strings
  ...

1 files changed, 114 insertions, 0 deletions

diff --git a/Documentation/i2c/busses/i2c-piix4.rst b/Documentation/i2c/busses/i2c-piix4.rst
new file mode 100644
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+=======================
+Kernel driver i2c-piix4
+=======================
+
+Supported adapters:
+  * Intel 82371AB PIIX4 and PIIX4E
+  * Intel 82443MX (440MX)
+    Datasheet: Publicly available at the Intel website
+  * ServerWorks OSB4, CSB5, CSB6, HT-1000 and HT-1100 southbridges
+    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, ML, CZ
+    Datasheet: Not publicly available
+  * Hygon CZ
+    Datasheet: Not publicly available
+  * Standard Microsystems (SMSC) SLC90E66 (Victory66) southbridge
+    Datasheet: Publicly available at the SMSC website http://www.smsc.com
+
+Authors:
+	- Frodo Looijaard <frodol@dds.nl>
+	- Philip Edelbrock <phil@netroedge.com>
+
+
+Module Parameters
+-----------------
+
+* force: int
+  Forcibly enable the PIIX4. DANGEROUS!
+* force_addr: int
+  Forcibly enable the PIIX4 at the given address. EXTREMELY DANGEROUS!
+
+
+Description
+-----------
+
+The PIIX4 (properly known as the 82371AB) is an Intel chip with a lot of
+functionality. Among other things, it implements the PCI bus. One of its
+minor functions is implementing a System Management Bus. This is a true
+SMBus - you can not access it on I2C levels. The good news is that it
+natively understands SMBus commands and you do not have to worry about
+timing problems. The bad news is that non-SMBus devices connected to it can
+confuse it mightily. Yes, this is known to happen...
+
+Do ``lspci -v`` and see whether it contains an entry like this::
+
+  0000:00:02.3 Bridge: Intel Corp. 82371AB/EB/MB PIIX4 ACPI (rev 02)
+	       Flags: medium devsel, IRQ 9
+
+Bus and device numbers may differ, but the function number must be
+identical (like many PCI devices, the PIIX4 incorporates a number of
+different 'functions', which can be considered as separate devices). If you
+find such an entry, you have a PIIX4 SMBus controller.
+
+On some computers (most notably, some Dells), the SMBus is disabled by
+default. If you use the insmod parameter 'force=1', the kernel module will
+try to enable it. THIS IS VERY DANGEROUS! If the BIOS did not set up a
+correct address for this module, you could get in big trouble (read:
+crashes, data corruption, etc.). Try this only as a last resort (try BIOS
+updates first, for example), and backup first! An even more dangerous
+option is 'force_addr=<IOPORT>'. This will not only enable the PIIX4 like
+'force' foes, but it will also set a new base I/O port address. The SMBus
+parts of the PIIX4 needs a range of 8 of these addresses to function
+correctly. If these addresses are already reserved by some other device,
+you will get into big trouble! DON'T USE THIS IF YOU ARE NOT VERY SURE
+ABOUT WHAT YOU ARE DOING!
+
+The PIIX4E is just an new version of the PIIX4; it is supported as well.
+The PIIX/PIIX3 does not implement an SMBus or I2C bus, so you can't use
+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, SB800, SP5100 and Hudson-2 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.
+
+1) Use lspci command and locate the PCI device with the SMBus controller:
+   00:0f.0 ISA bridge: ServerWorks OSB4 South Bridge (rev 4f)
+   The line may vary for different chipsets. Please consult the driver source
+   for all possible PCI ids (and lspci -n to match them). Lets assume the
+   device is located at 00:0f.0.
+2) Now you just need to change the value in 0xD2 register. Get it first with
+   command: lspci -xxx -s 00:0f.0
+   If the value is 0x3 then you need to change it to 0x1:
+   setpci  -s 00:0f.0 d2.b=1
+
+Please note that you don't need to do that in all cases, just when the SMBus is
+not working properly.
+
+
+Hardware-specific issues
+------------------------
+
+This driver will refuse to load on IBM systems with an Intel PIIX4 SMBus.
+Some of these machines have an RFID EEPROM (24RF08) connected to the SMBus,
+which can easily get corrupted due to a state machine bug. These are mostly
+Thinkpad laptops, but desktop systems may also be affected. We have no list
+of all affected systems, so the only safe solution was to prevent access to
+the SMBus on all IBM systems (detected using DMI data.)
+
+For additional information, read:
+http://www.lm-sensors.org/browser/lm-sensors/trunk/README