From: Quentin Schulz <quentin.schulz@xxxxxxxxx> A few of the I2C GPIO expander chips supported by this binding have a RESETN pin to be able to reset the chip. The chip is held in reset while the pin is low, therefore the polarity of reset-gpios is expected to reflect that, i.e. a GPIO_ACTIVE_HIGH means the GPIO will be held low for reset and released high, GPIO_ACTIVE_LOW means the GPIO will be held high for reset and released low. Out of the supported chips, only PCA9670, PCA9671, PCA9672 and PCA9673 show a RESETN pin in their datasheets. They all share the same reset timings, that is 4+us reset pulse[0] and 100+us reset time[0]. When performing a reset, "The PCA9670 registers and I2C-bus state machine will be held in their default state until the RESET input is once again HIGH."[1] meaning we now know the state of each line controlled by the GPIO expander. Therefore, setting lines-initial-states and reset-gpios both does not make sense and their presence is XOR'ed. [0] https://www.nxp.com/docs/en/data-sheet/PCA9670.pdf Fig 22. [1] https://www.nxp.com/docs/en/data-sheet/PCA9670.pdf 8.5 Signed-off-by: Quentin Schulz <quentin.schulz@xxxxxxxxx> --- .../devicetree/bindings/gpio/nxp,pcf8575.yaml | 33 ++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/Documentation/devicetree/bindings/gpio/nxp,pcf8575.yaml b/Documentation/devicetree/bindings/gpio/nxp,pcf8575.yaml index 3718103e966a13e1d77f73335ff73c18a3199469..d08d3f848f82e74de949da16d26a810dc52a74e5 100644 --- a/Documentation/devicetree/bindings/gpio/nxp,pcf8575.yaml +++ b/Documentation/devicetree/bindings/gpio/nxp,pcf8575.yaml @@ -73,6 +73,39 @@ properties: wakeup-source: true + reset-gpios: + maxItems: 1 + description: + GPIO controlling the (reset active LOW) RESET# pin. + + Performing a reset makes all lines initialized to their input (pulled-up) + state. + +allOf: + - if: + properties: + compatible: + not: + contains: + enum: + - nxp,pca9670 + - nxp,pca9671 + - nxp,pca9672 + - nxp,pca9673 + then: + properties: + reset-gpios: false + + # lines-initial-states XOR reset-gpios + # Performing a reset reinitializes all lines to a known state which + # may not match passed lines-initial-states + - if: + required: + - lines-initial-states + then: + properties: + reset-gpios: false + patternProperties: "^(.+-hog(-[0-9]+)?)$": type: object -- 2.48.1