diff options
Diffstat (limited to 'Documentation/devicetree/bindings/i2c')
3 files changed, 83 insertions, 1 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 0000000..1ac8ea8 --- /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 + }; + }; + }; diff --git a/Documentation/devicetree/bindings/i2c/i2c-s3c2410.txt b/Documentation/devicetree/bindings/i2c/i2c-s3c2410.txt index f98d4c5..296eb45 100644 --- a/Documentation/devicetree/bindings/i2c/i2c-s3c2410.txt +++ b/Documentation/devicetree/bindings/i2c/i2c-s3c2410.txt @@ -26,7 +26,7 @@ Required for all cases except "samsung,s3c2440-hdmiphy-i2c": - pinctrl-names: Should contain only one value - "default". Optional properties: - - samsung,i2c-slave-addr: Slave address in multi-master enviroment. If not + - samsung,i2c-slave-addr: Slave address in multi-master environment. If not specified, default value is 0. - samsung,i2c-max-bus-freq: Desired frequency in Hz of the bus. If not specified, the default value in Hz is 100000. diff --git a/Documentation/devicetree/bindings/i2c/trivial-devices.txt b/Documentation/devicetree/bindings/i2c/trivial-devices.txt index 446859f..ad6a738 100644 --- a/Documentation/devicetree/bindings/i2c/trivial-devices.txt +++ b/Documentation/devicetree/bindings/i2c/trivial-devices.txt @@ -35,6 +35,8 @@ fsl,mc13892 MC13892: Power Management Integrated Circuit (PMIC) for i.MX35/51 fsl,mma8450 MMA8450Q: Xtrinsic Low-power, 3-axis Xtrinsic Accelerometer fsl,mpr121 MPR121: Proximity Capacitive Touch Sensor Controller fsl,sgtl5000 SGTL5000: Ultra Low-Power Audio Codec +infineon,slb9635tt Infineon SLB9635 (Soft-) I2C TPM (old protocol, max 100khz) +infineon,slb9645tt Infineon SLB9645 I2C TPM (new protocol, max 400khz) maxim,ds1050 5 Bit Programmable, Pulse-Width Modulator maxim,max1237 Low-Power, 4-/12-Channel, 2-Wire Serial, 12-Bit ADCs maxim,max6625 9-Bit/12-Bit Temperature Sensors with I²C-Compatible Serial Interface |