Merge branch 'i2c/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux

Pull i2c changes from Wolfram Sang:

 - an arbitration driver.  While the driver is quite simple, it caused
   discussion if we need additional arbitration on top of the one
   specified in the I2C standard.  Conclusion is that I accept a few
   generic mechanisms, but not very specific ones.

 - the core lost the detach_adapter() call.  It has no users anymore and
   was in the way for other cleanups.  attach_adapter() is sadly still
   there since there are users waiting to be converted.

 - the core gained a bus recovery infrastructure.  I2C defines a way to
   recover if the data line is stalled.  This mechanism is now in the
   core and drivers can now pass some data to make use of it.

 - bigger driver cleanups for designware, s3c2410

 - removing superfluous refcounting from drivers

 - removing Ben Dooks as second maintainer due to inactivity.  Thanks
   for all your work so far, Ben!

 - bugfixes, feature additions, devicetree fixups, simplifications...

* 'i2c/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux: (38 commits)
  i2c: xiic: must always write 16-bit words to TX_FIFO
  i2c: octeon: use HZ in timeout value
  i2c: octeon: Fix i2c fail problem when a process is terminated by a signal
  i2c: designware-pci: drop superfluous {get|put}_device
  i2c: designware-plat: drop superfluous {get|put}_device
  i2c: davinci: drop superfluous {get|put}_device
  MAINTAINERS: Ben Dooks is inactive regarding I2C
  i2c: mux: Add i2c-arb-gpio-challenge 'mux' driver
  i2c: at91: convert to dma_request_slave_channel_compat()
  i2c: mxs: do error checking and handling in PIO mode
  i2c: mxs: remove races in PIO code
  i2c-designware: switch to use runtime PM autosuspend
  i2c-designware: use usleep_range() in the busy-loop
  i2c-designware: enable/disable the controller properly
  i2c-designware: use dynamic adapter numbering on Lynxpoint
  i2c-designware-pci: use managed functions pcim_* and devm_*
  i2c-designware-pci: use dev_err() instead of printk()
  i2c-designware: move to managed functions (devm_*)
  i2c: remove CONFIG_HOTPLUG ifdefs
  i2c: s3c2410: Add SMBus emulation for block read
  ...

1 files changed, 80 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt b/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt
new file mode 100644
index 000000000000..1ac8ea8ade1d
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt
@@ -0,0 +1,80 @@
+GPIO-based I2C Arbitration Using a Challenge & Response Mechanism
+=================================================================
+This uses GPIO lines and a challenge & response mechanism to arbitrate who is
+the master of an I2C bus in a multimaster situation.
+
+In many cases using GPIOs to arbitrate is not needed and a design can use
+the standard I2C multi-master rules.  Using GPIOs is generally useful in
+the case where there is a device on the bus that has errata and/or bugs
+that makes standard multimaster mode not feasible.
+
+
+Algorithm:
+
+All masters on the bus have a 'bus claim' line which is an output that the
+others can see. These are all active low with pull-ups enabled.  We'll
+describe these lines as:
+
+- OUR_CLAIM: output from us signaling to other hosts that we want the bus
+- THEIR_CLAIMS: output from others signaling that they want the bus
+
+The basic algorithm is to assert your line when you want the bus, then make
+sure that the other side doesn't want it also.  A detailed explanation is best
+done with an example.
+
+Let's say we want to claim the bus.  We:
+1. Assert OUR_CLAIM.
+2. Waits a little bit for the other sides to notice (slew time, say 10
+   microseconds).
+3. Check THEIR_CLAIMS.  If none are asserted then the we have the bus and we are
+   done.
+4. Otherwise, wait for a few milliseconds and see if THEIR_CLAIMS are released.
+5. If not, back off, release the claim and wait for a few more milliseconds.
+6. Go back to 1 (until retry time has expired).
+
+
+Required properties:
+- compatible: i2c-arb-gpio-challenge
+- our-claim-gpio: The GPIO that we use to claim the bus.
+- their-claim-gpios: The GPIOs that the other sides use to claim the bus.
+  Note that some implementations may only support a single other master.
+- Standard I2C mux properties. See mux.txt in this directory.
+- Single I2C child bus node at reg 0. See mux.txt in this directory.
+
+Optional properties:
+- slew-delay-us: microseconds to wait for a GPIO to go high. Default is 10 us.
+- wait-retry-us: we'll attempt another claim after this many microseconds.
+    Default is 3000 us.
+- wait-free-us: we'll give up after this many microseconds. Default is 50000 us.
+
+
+Example:
+	i2c@12CA0000 {
+		compatible = "acme,some-i2c-device";
+		#address-cells = <1>;
+		#size-cells = <0>;
+	};
+
+	i2c-arbitrator {
+		compatible = "i2c-arb-gpio-challenge";
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		i2c-parent = <&{/i2c@12CA0000}>;
+
+		our-claim-gpio = <&gpf0 3 1>;
+		their-claim-gpios = <&gpe0 4 1>;
+		slew-delay-us = <10>;
+		wait-retry-us = <3000>;
+		wait-free-us = <50000>;
+
+		i2c@0 {
+			reg = <0>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			i2c@52 {
+				// Normal I2C device
+			};
+		};
+	};