From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Thomas Petazzoni Subject: [PATCH 1/4] dt-bindings: gpio: document the new pull-up/pull-down flags Date: Thu, 3 Jan 2019 17:40:59 +0100 Message-Id: <20190103164102.31437-2-thomas.petazzoni@bootlin.com> In-Reply-To: <20190103164102.31437-1-thomas.petazzoni@bootlin.com> References: <20190103164102.31437-1-thomas.petazzoni@bootlin.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To: Linus Walleij , Bartosz Golaszewski , Rob Herring , Mark Rutland Cc: Frank Rowand , linux-gpio@vger.kernel.org, devicetree@vger.kernel.org, Marek Vasut , Thomas Petazzoni List-ID: This commit extends the flags that can be used in GPIO specifiers to indicate if a pull-up resistor or pull-down resistor should be enabled. While some pinctrl DT bindings already offer the capability of configuring pull-up/pull-down resistors at the pin level, a number of simple GPIO controllers don't have any pinmuxing capability, and therefore do not rely on the pinctrl DT bindings. Such simple GPIO controllers however sometimes allow to configure pull-up and pull-down resistors on a per-pin basis, and whether such resistors should be enabled or not is a highly board-specific HW characteristic. By using two additional bits of the GPIO flag specifier, we can easily allow the Device Tree to describe which GPIOs should have their pull-up or pull-down resistors enabled. Even though the two options are mutually exclusive, we still need two bits to encode at least three states: no pull-up/pull-down, pull-up, pull-down. Signed-off-by: Thomas Petazzoni --- Documentation/devicetree/bindings/gpio/gpio.txt | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt index f0ba154b5723..03d8adf67c16 100644 --- a/Documentation/devicetree/bindings/gpio/gpio.txt +++ b/Documentation/devicetree/bindings/gpio/gpio.txt @@ -67,6 +67,10 @@ Optional standard bitfield specifiers for the last cell: https://en.wikipedia.org/wiki/Open_collector - Bit 3: 0 means the output should be maintained during sleep/low-power mode 1 means the output state can be lost during sleep/low-power mode +- Bit 4: 0 means no pull-up resistor should be enabled + 1 means a pull-up resistor should be enabled +- Bit 5: 0 means no pull-down resistor should be enabled + 1 means a pull-down resistor should be enabled 1.1) GPIO specifier best practices ---------------------------------- -- 2.20.1