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From: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
To: Linus Walleij <linus.walleij@linaro.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>
Cc: Frank Rowand <frowand.list@gmail.com>,
	linux-gpio@vger.kernel.org, devicetree@vger.kernel.org,
	Marek Vasut <marek.vasut@gmail.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: [PATCH 1/4] dt-bindings: gpio: document the new pull-up/pull-down flags
Date: Thu,  3 Jan 2019 17:40:59 +0100	[thread overview]
Message-ID: <20190103164102.31437-2-thomas.petazzoni@bootlin.com> (raw)
In-Reply-To: <20190103164102.31437-1-thomas.petazzoni@bootlin.com>

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 <thomas.petazzoni@bootlin.com>
---
 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

  reply	other threads:[~2019-01-03 16:40 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-03 16:40 [PATCH 0/4] Proposal to support pull-up/pull-down GPIO configuration Thomas Petazzoni
2019-01-03 16:40 ` Thomas Petazzoni [this message]
2019-01-11  9:57   ` [PATCH 1/4] dt-bindings: gpio: document the new pull-up/pull-down flags Linus Walleij
2019-01-03 16:41 ` [PATCH 2/4] gpio: rename gpio_set_drive_single_ended() to gpio_set_config() Thomas Petazzoni
2019-01-11 10:01   ` Linus Walleij
2019-01-03 16:41 ` [PATCH 3/4] gpio: add core support for pull-up/pull-down configuration Thomas Petazzoni
2019-01-08 14:00   ` Jan Kundrát
2019-01-08 14:04     ` Thomas Petazzoni
2019-01-11 10:11       ` Linus Walleij
2019-01-11 10:05   ` Linus Walleij
2019-01-11 12:58     ` Thomas Petazzoni
2019-01-11 14:38       ` Linus Walleij
2019-01-11 16:41   ` Rob Herring
2019-01-03 16:41 ` [PATCH 4/4] gpio: pca953x: add ->set_config implementation Thomas Petazzoni
2019-01-11 10:14   ` Linus Walleij
2019-02-07 14:44     ` Thomas Petazzoni

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