From: Mauri Sandberg <maukka@ext.kapsi.fi>
To: sandberg@mailfence.com
Cc: andy.shevchenko@gmail.com, bgolaszewski@baylibre.com,
geert+renesas@glider.be, linus.walleij@linaro.org,
linux-gpio@vger.kernel.org, robh+dt@kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
drew@beagleboard.org, Mauri Sandberg <maukka@ext.kapsi.fi>
Subject: [PATCH v5 1/2] dt-bindings: gpio-cascade: add documentation
Date: Mon, 21 Jun 2021 20:20:52 +0300 [thread overview]
Message-ID: <20210621172053.107045-2-maukka@ext.kapsi.fi> (raw)
In-Reply-To: <20210621172053.107045-1-maukka@ext.kapsi.fi>
Add documentation for a general GPIO cascade. It allows building
one-to-many cascades of GPIO lines using multiplexer to choose
the cascaded line.
Signed-off-by: Mauri Sandberg <maukka@ext.kapsi.fi>
---
v4 -> v5:
- renamed gpio-mux-input -> gpio-cascade
- changed vague term 'pin' to 'upstream line'
- added more verbose description for the module
- added missing 'mux-controls' entry
- dropped Tested-by and Reviewed-by due to changes in bindings
v3 -> v4:
- Changed author email
- Included Tested-by and Reviewed-by from Drew
v2 -> v3: added a complete example on dual 4-way multiplexer
v1 -> v2: added a little bit more text in the binding documenation
---
.../bindings/gpio/gpio-cascade.yaml | 103 ++++++++++++++++++
1 file changed, 103 insertions(+)
create mode 100644 Documentation/devicetree/bindings/gpio/gpio-cascade.yaml
diff --git a/Documentation/devicetree/bindings/gpio/gpio-cascade.yaml b/Documentation/devicetree/bindings/gpio/gpio-cascade.yaml
new file mode 100644
index 000000000000..46248f8e2ba5
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-cascade.yaml
@@ -0,0 +1,103 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/gpio/gpio-cascade.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic GPIO cascade
+
+maintainers:
+ - Mauri Sandberg <maukka@ext.kapsi.fi>
+
+description: |
+ A generic GPIO cascade
+
+ This hardware construction cascades (multiplexes) several GPIO lines from
+ one-to-many using a software controlled multiplexer. The most common use
+ case is probably reading several inputs by switching the multiplexer over
+ several input lines, which in practice works well since input lines has
+ high impedance.
+
+ Constructions with multiplexed outputs are also possible using open drain
+ electronics.
+
+ The number of cascaded GPIO lines is limited by the technology used to
+ switch over the cascaded lines. There are readily available dual/triple
+ 4-to-1 multiplexers, for example, and others.
+
+ Illustration (pins used to drive the multiplexer are omitted for clarity)
+
+ /|---- Cascaded GPIO line 0
+ Upstream | |---- Cascaded GPIO line 1
+ GPIO line ----+ | .
+ | | .
+ \|---- Cascaded GPIO line n
+
+properties:
+ compatible:
+ enum:
+ - gpio-cascade
+
+ gpio-controller: true
+
+ '#gpio-cells':
+ const: 2
+
+ mux-controls:
+ minItems: 1
+ maxItems: 1
+ description: |
+ The mux controller that will be driving the GPIO cascade.
+
+ upstream-gpios:
+ description: |
+ The GPIO line used as the upstream line will convey the status to/from
+ cascaded GPIO lines. In an input mode, by using this line, it is
+ possible to read the status from selected cascaded GPIO line.
+
+ In an output mode the status of the upstream GPIO will be conveyed to
+ the selected cascaded GPIO line.
+
+required:
+ - compatible
+ - gpio-controller
+ - "#gpio-cells"
+ - mux-controls
+ - upstream-gpios
+
+additionalProperties: false
+
+examples:
+ - |
+ #include <dt-bindings/gpio/gpio.h>
+ mux: mux-controller {
+ compatible = "gpio-mux";
+ #mux-control-cells = <0>;
+
+ mux-gpios = <&gpio 9 GPIO_ACTIVE_HIGH>,
+ <&gpio 11 GPIO_ACTIVE_HIGH>;
+ };
+
+ gpio2: key-mux1 {
+ compatible = "gpio-cascade";
+ mux-controls = <&mux>;
+
+ gpio-controller;
+ #gpio-cells = <2>;
+
+ // GPIOs used by this node, upstream pin
+ upstream-gpios = <&gpio 12 GPIO_ACTIVE_HIGH>;
+ };
+
+ gpio3: key-mux2 {
+ compatible = "gpio-cascade";
+ mux-controls = <&mux>;
+
+ gpio-controller;
+ #gpio-cells = <2>;
+
+ // GPIOs used by this node, upstream pin
+ upstream-gpios = <&gpio 14 GPIO_ACTIVE_HIGH>;
+ };
+
+...
--
2.25.1
next prev parent reply other threads:[~2021-06-21 17:25 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210325122832.119147-1-sandberg@mailfence.com>
2021-05-30 16:13 ` [PATCH v4 0/2] gpio: add generic gpio input multiplexer Mauri Sandberg
2021-05-30 16:13 ` [PATCH v4 1/2] dt-bindings: gpio-mux-input: add documentation Mauri Sandberg
2021-06-01 10:10 ` Linus Walleij
2021-06-01 10:44 ` Linus Walleij
2021-06-02 9:31 ` Mauri Sandberg
2021-06-02 10:35 ` Linus Walleij
2021-06-02 11:21 ` Mauri Sandberg
2021-06-04 7:51 ` Linus Walleij
2021-06-01 13:32 ` Rob Herring
2021-06-02 11:36 ` Mauri Sandberg
2021-05-30 16:13 ` [PATCH v4 2/2] gpio: gpio-mux-input: add generic gpio input multiplexer Mauri Sandberg
2021-05-30 18:09 ` Andy Shevchenko
2021-05-30 19:02 ` Mauri Sandberg
2021-05-30 19:38 ` Andy Shevchenko
2021-05-31 10:19 ` Mauri Sandberg
2021-06-01 10:38 ` Linus Walleij
2021-06-21 17:20 ` [PATCH v5 0/2] gpio: add generic gpio cascade Mauri Sandberg
2021-06-21 17:20 ` Mauri Sandberg [this message]
2021-06-24 18:30 ` [PATCH v5 1/2] dt-bindings: gpio-cascade: add documentation Rob Herring
2021-06-21 17:20 ` [PATCH v5 2/2] gpio: gpio-cascade: add generic GPIO cascade Mauri Sandberg
2021-06-21 17:43 ` Andy Shevchenko
2021-06-21 18:31 ` Enrico Weigelt, metux IT consult
2021-10-15 12:56 ` Mauri Sandberg
2021-10-15 17:20 ` Andy Shevchenko
2021-10-19 12:57 ` [PATCH v6 0/2] " Mauri Sandberg
2021-10-19 12:57 ` [PATCH v6 1/2] dt-bindings: gpio-cascade: add documentation Mauri Sandberg
2021-10-19 12:57 ` [PATCH v6 2/2] gpio: gpio-cascade: add generic GPIO cascade Mauri Sandberg
2021-10-19 13:12 ` Andy Shevchenko
2021-10-19 20:08 ` [PATCH v7 0/2] " Mauri Sandberg
2021-10-19 20:08 ` [PATCH v7 1/2] dt-bindings: gpio-cascade: add documentation Mauri Sandberg
2021-10-24 22:18 ` Linus Walleij
2021-10-19 20:08 ` [PATCH v7 2/2] gpio: gpio-cascade: add generic GPIO cascade Mauri Sandberg
2021-10-24 22:17 ` Linus Walleij
2021-10-25 9:29 ` Andy Shevchenko
2021-10-26 19:15 ` [PATCH v8 0/2] " Mauri Sandberg
2021-10-26 19:15 ` [PATCH v8 1/2] dt-bindings: gpio-cascade: add documentation Mauri Sandberg
2021-10-26 19:15 ` [PATCH v8 2/2] gpio: gpio-cascade: add generic GPIO cascade Mauri Sandberg
2022-02-05 21:59 ` [RESEND v8 0/2] " Mauri Sandberg
2022-02-05 21:59 ` [RESEND v8 1/2] dt-bindings: gpio-cascade: add documentation Mauri Sandberg
2022-02-05 21:59 ` [RESEND v8 2/2] gpio: gpio-cascade: add generic GPIO cascade Mauri Sandberg
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