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Commit 99bece77 authored by Linus Torvalds's avatar Linus Torvalds
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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
  ...
parents 736a2dd2 c39e8e43

Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt

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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

			};

		};

	};

MAINTAINERS

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@@ -3919,7 +3919,6 @@ F: drivers/i2c/i2c-stub.c 


I2C SUBSYSTEM

M:	Wolfram Sang <wsa@the-dreams.de>

M:	"Ben Dooks (embedded platforms)" <ben-linux@fluff.org>

L:	linux-i2c@vger.kernel.org

W:	http://i2c.wiki.kernel.org/

T:	git git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git

arch/arm/mach-s3c24xx/mach-rx1950.c

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@@ -56,7 +56,6 @@ 
#include <plat/cpu.h>

#include <plat/devs.h>

#include <plat/pm.h>

#include <plat/regs-iic.h>

#include <plat/regs-serial.h>



#include "common.h"

arch/arm/mach-tegra/tegra.c

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@@ -31,8 +31,6 @@ 
#include <linux/pda_power.h>

#include <linux/platform_data/tegra_usb.h>

#include <linux/io.h>

#include <linux/i2c.h>

#include <linux/i2c-tegra.h>

#include <linux/slab.h>

#include <linux/sys_soc.h>

#include <linux/usb/tegra_usb_phy.h>

arch/arm/plat-samsung/devs.c

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@@ -63,7 +63,6 @@ 
#include <linux/platform_data/usb-s3c2410_udc.h>

#include <linux/platform_data/usb-ohci-s3c2410.h>

#include <plat/usb-phy.h>

#include <plat/regs-iic.h>

#include <plat/regs-serial.h>

#include <plat/regs-spi.h>

#include <linux/platform_data/spi-s3c64xx.h>