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([178.197.223.104]) by smtp.gmail.com with ESMTPSA id d12-20020a17090648cc00b00992b7ff3993sm3281038ejt.126.2023.07.22.02.57.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 22 Jul 2023 02:57:14 -0700 (PDT) From: Krzysztof Kozlowski To: Peter Rosin , Andi Shyti , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Doug Anderson , linux-i2c@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Krzysztof Kozlowski Subject: [PATCH 2/2] dt-bindings: i2c: arb-gpio-challange: convert to DT schema Date: Sat, 22 Jul 2023 11:57:10 +0200 Message-Id: <20230722095710.17496-2-krzysztof.kozlowski@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230722095710.17496-1-krzysztof.kozlowski@linaro.org> References: <20230722095710.17496-1-krzysztof.kozlowski@linaro.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Convert the bindings for GPIO-based I2C Arbitration Using a Challenge & Response Mechanism to DT schema. Signed-off-by: Krzysztof Kozlowski Acked-by: Douglas Anderson --- The text of original bindings was written by Doug, so please kindly ack if you agree to relicense it from GPL-2 to (GPL-2.0-only OR BSD-2-Clause). Changes in v2: 1. Drop i2c-controller $ref in top-level part, because only children are I2C controllers. 2. Add Ack. --- .../bindings/i2c/i2c-arb-gpio-challenge.txt | 82 ----------- .../bindings/i2c/i2c-arb-gpio-challenge.yaml | 135 ++++++++++++++++++ .../devicetree/bindings/i2c/i2c-arb.txt | 35 ----- 3 files changed, 135 insertions(+), 117 deletions(-) delete mode 100644 Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt create mode 100644 Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.yaml delete mode 100644 Documentation/devicetree/bindings/i2c/i2c-arb.txt diff --git a/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt b/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt deleted file mode 100644 index 548a73cde796..000000000000 --- a/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.txt +++ /dev/null @@ -1,82 +0,0 @@ -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. - -Note that this scheme works well enough but has some downsides: -* It is nonstandard (not using standard I2C multimaster) -* Having two masters on a bus in general makes it relatively hard to debug - problems (hard to tell if i2c issues were caused by one master, another, or - some device on the bus). - - -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. -- I2C arbitration bus node. See i2c-arb.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"; - - 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-arb { - #address-cells = <1>; - #size-cells = <0>; - - i2c@52 { - // Normal I2C device - }; - }; - }; diff --git a/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.yaml b/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.yaml new file mode 100644 index 000000000000..5bf6ce14c2dc --- /dev/null +++ b/Documentation/devicetree/bindings/i2c/i2c-arb-gpio-challenge.yaml @@ -0,0 +1,135 @@ +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/i2c/i2c-arb-gpio-challenge.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: GPIO-based I2C Arbitration Using a Challenge & Response Mechanism + +maintainers: + - Doug Anderson + - Peter Rosin + +description: | + 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. + + Note that this scheme works well enough but has some downsides: + * It is nonstandard (not using standard I2C multimaster) + * Having two masters on a bus in general makes it relatively hard to debug + problems (hard to tell if i2c issues were caused by one master, another, + or some device on the bus). + + 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). + +properties: + compatible: + const: i2c-arb-gpio-challenge + + i2c-parent: + $ref: /schemas/types.yaml#/definitions/phandle + description: + The I2C bus that this multiplexer's master-side port is connected to. + + our-claim-gpios: + maxItems: 1 + description: + The GPIO that we use to claim the bus. + + slew-delay-us: + default: 10 + description: + Time to wait for a GPIO to go high. + + their-claim-gpios: + minItems: 1 + maxItems: 2 + description: + The GPIOs that the other sides use to claim the bus. Note that some + implementations may only support a single other master. + + wait-free-us: + default: 50000 + description: + We'll give up after this many microseconds. + + wait-retry-us: + default: 3000 + description: + We'll attempt another claim after this many microseconds. + + i2c-arb: + type: object + $ref: /schemas/i2c/i2c-controller.yaml + unevaluatedProperties: false + description: + I2C arbitration bus node. + +required: + - compatible + - i2c-arb + - our-claim-gpios + - their-claim-gpios + +additionalProperties: false + +examples: + - | + #include + #include + + i2c-arbitrator { + compatible = "i2c-arb-gpio-challenge"; + i2c-parent = <&i2c_4>; + + our-claim-gpios = <&gpf0 3 GPIO_ACTIVE_LOW>; + their-claim-gpios = <&gpe0 4 GPIO_ACTIVE_LOW>; + slew-delay-us = <10>; + wait-retry-us = <3000>; + wait-free-us = <50000>; + + i2c-arb { + #address-cells = <1>; + #size-cells = <0>; + + sbs-battery@b { + compatible = "sbs,sbs-battery"; + reg = <0xb>; + sbs,poll-retry-count = <1>; + }; + + embedded-controller@1e { + compatible = "google,cros-ec-i2c"; + reg = <0x1e>; + interrupts = <6 IRQ_TYPE_LEVEL_HIGH>; + interrupt-parent = <&gpx1>; + pinctrl-names = "default"; + pinctrl-0 = <&ec_irq>; + wakeup-source; + }; + }; + }; diff --git a/Documentation/devicetree/bindings/i2c/i2c-arb.txt b/Documentation/devicetree/bindings/i2c/i2c-arb.txt deleted file mode 100644 index 59abf9277bdc..000000000000 --- a/Documentation/devicetree/bindings/i2c/i2c-arb.txt +++ /dev/null @@ -1,35 +0,0 @@ -Common i2c arbitration bus properties. - -- i2c-arb child node - -Required properties for the i2c-arb child node: -- #address-cells = <1>; -- #size-cells = <0>; - -Optional properties for i2c-arb child node: -- Child nodes conforming to i2c bus binding - - -Example : - - /* - An NXP pca9541 I2C bus master selector at address 0x74 - with a NXP pca8574 GPIO expander attached. - */ - - arb@74 { - compatible = "nxp,pca9541"; - reg = <0x74>; - - i2c-arb { - #address-cells = <1>; - #size-cells = <0>; - - gpio@38 { - compatible = "nxp,pca8574"; - reg = <0x38>; - #gpio-cells = <2>; - gpio-controller; - }; - }; - };