linux-kernel - [PATCH 1/2] dt-bindings: reset: Add generic GPIO reset binding

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Date:   Mon, 18 Oct 2021 19:49:21 -0400
From:   Sean Anderson <sean.anderson@...o.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Sean Anderson <sean.anderson@...o.com>,
        Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org
Subject: [PATCH 1/2] dt-bindings: reset: Add generic GPIO reset binding

This adds a binding for a generic GPIO reset driver. This driver is
designed to easily add a GPIO-based reset to a driver which expected a
reset controller. It offers greater flexibility than a reset-gpios
property, and allows for one code path to be shared for GPIO resets and
MMIO-based resets.

Signed-off-by: Sean Anderson <sean.anderson@...o.com>
---

 .../devicetree/bindings/reset/gpio-reset.yaml | 93 +++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/reset/gpio-reset.yaml

diff --git a/Documentation/devicetree/bindings/reset/gpio-reset.yaml b/Documentation/devicetree/bindings/reset/gpio-reset.yaml
new file mode 100644
index 000000000000..de2ab074cea3
--- /dev/null
+++ b/Documentation/devicetree/bindings/reset/gpio-reset.yaml
@@ -0,0 +1,93 @@
+# SPDX-License-Identifier: (GPL-2.0+ OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/reset/gpio-reset.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic GPIO reset driver
+
+maintainers:
+  - Sean Anderson <seanga2@...il.com>
+
+description: |
+  This is a generic GPIO reset driver which can provide a reset-controller
+  interface for GPIO-based reset lines. This driver always operates with
+  logical GPIO values; to invert the polarity, specify GPIO_ACTIVE_LOW in the
+  GPIO's flags.
+
+properties:
+  compatible:
+    const: gpio-reset
+
+  '#reset-cells':
+    const: 1
+
+  reset-gpios:
+    description: |
+      GPIOs to assert when asserting a reset. There is a one-to-one mapping
+      between the reset specifier and the index of the GPIO in this list to
+      assert.
+
+  done-gpios:
+    description: |
+      GPIOs which indicate that the device controlled by the GPIO has exited
+      reset. There must be one done GPIO for each reset GPIO, or no done GPIOs
+      at all. The driver will wait for up to done-timeout-us for the
+      corresponding done GPIO to assert before returning.
+
+  pre-assert-us:
+    default: 0
+    description: |
+      Microseconds to delay between when the reset was requested to be
+      asserted, and asserting the reset GPIO
+
+  post-assert-us:
+    default: 0
+    description: |
+      Microseconds to delay after asserting the reset GPIO and before returning
+      to the caller.
+
+  pre-deassert-us:
+    default: 0
+    description: |
+      Microseconds to delay between when the reset was requested to be
+      deasserted, and asserting the reset GPIO
+
+  post-deassert-us:
+    default: 0
+    description: |
+      Microseconds to delay after deasserting the reset GPIO and before
+      returning to the caller. This delay is always present, even if the done
+      GPIO goes high earlier.
+
+  done-timeout-us:
+    default: 1000
+    description:
+      Microseconds to wait for the done GPIO to assert after deasserting the
+      reset GPIO. If post-deassert-us is present, this property defaults to 10
+      times that delay. The timeout starts after waiting for the post deassert
+      delay.
+
+required:
+  - '#reset-cells'
+  - compatible
+  - reset-gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    pcs_reset: reset-pcs {
+        #reset-cells = <1>;
+        compatible = "gpio-reset";
+        reset-gpios = <&gpio 0 GPIO_ACTIVE_LOW>,
+                      <&gpio 1 GPIO_ACTIVE_LOW>,
+                      <&gpio 2 GPIO_ACTIVE_LOW>,
+                      <&gpio 3 GPIO_ACTIVE_LOW>;
+        done-gpios = <&gpio 4 GPIO_ACTIVE_HIGH>,
+                     <&gpio 5 GPIO_ACTIVE_HIGH>,
+                     <&gpio 6 GPIO_ACTIVE_HIGH>,
+                     <&gpio 7 GPIO_ACTIVE_HIGH>;
+        post-deassert-us = <100>;
+    };
-- 
2.25.1