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counter: add GPIO-based quadrature encoder driver

PATCH Superseded Wadim Mueller 2 participants 5 messages Apr 19 – Apr 20

Subsystems (3)
Device tree bindings IIO Counter

v2 of 7 Superseded Latest is v7 →

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Wadim Mueller

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#0 lore raw

v2 cover counter: add GPIO-based quadrature encoder driver

This series adds a new counter subsystem driver that implements quadrature encoder position tracking using plain GPIO pins with edge-triggered interrupts.

The driver is intended for low to medium speed rotary encoders where hardware counter peripherals (eQEP, FTM, etc.) are unavailable or already in use. It targets the same use-cases as interrupt-cnt.c but provides full quadrature decoding instead of simple pulse counting.

Features:
- X1, X2, X4 quadrature decoding and pulse-direction mode
- Optional index signal for zero-reset
- Configurable ceiling (position clamping)
- Standard counter subsystem sysfs + chrdev interface
- Enable/disable via sysfs with IRQ gating

Tested on TI AM64x (Cortex-A53) with a motor-driven rotary encoder at up to 2 kHz quadrature edge rate.

Changes in v2:
- DT binding: rephrase description to describe hardware, not driver/sysfs behaviour (Conor Dooley)
- DT binding: drop redundant example without index GPIO (Conor Dooley)

Wadim Mueller (3):
dt-bindings: counter: add gpio-quadrature-encoder binding
counter: add GPIO-based quadrature encoder driver
MAINTAINERS: add entry for GPIO quadrature encoder counter driver

 .../counter/gpio-quadrature-encoder.yaml      |  60 ++
 MAINTAINERS                                   |   7 +
 drivers/counter/Kconfig                       |  15 +
 drivers/counter/Makefile                      |   1 +
 drivers/counter/gpio-quadrature-encoder.c     | 710 ++++++++++++++++++
 5 files changed, 793 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/counter/gpio-quadrature-encoder.yaml
 create mode 100644 drivers/counter/gpio-quadrature-encoder.c
Signature · 1 line
2.52.0
author
#1 lore raw

PATCH v2 1/3 dt-bindings: counter: add gpio-quadrature-encoder binding

Add devicetree binding documentation for the GPIO-based quadrature encoder counter driver. The driver reads A/B quadrature signals and an optional index pulse via edge-triggered GPIO interrupts, supporting X1, X2, X4 quadrature decoding and pulse-direction mode.

This is useful on SoCs that lack a dedicated hardware quadrature decoder or where the encoder is wired to generic GPIO pins.

Signed-off-by Wadim Mueller <[email protected]>
---
 .../counter/gpio-quadrature-encoder.yaml      | 60 +++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/counter/gpio-quadrature-encoder.yaml
Documentation/devicetree/bindings/counter/gpio-quadrature-encoder.yaml new file +60 -0
new file mode 100644
index 000000000..741396b29
@@ -0,0 +1,60 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/counter/gpio-quadrature-encoder.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: GPIO-based Quadrature Encoder
+
+maintainers:
+  - Wadim Mueller <[email protected]>
+
+description: |
+  A generic GPIO-based quadrature encoder counter.  Reads A/B quadrature
+  signals and an optional index pulse via edge-triggered GPIO interrupts.
+  Supports X1, X2, X4 quadrature decoding and pulse-direction mode.
+
+  This is useful on SoCs that lack a dedicated hardware quadrature
+  decoder (eQEP, QEI, etc.) or where the encoder is wired to generic
+  GPIO pins rather than to a dedicated peripheral.
+
+properties:
+  compatible:
+    const: gpio-quadrature-encoder
+
+  encoder-a-gpios:
+    maxItems: 1
+    description:
+      GPIO connected to the encoder's A (phase A) output.
+
+  encoder-b-gpios:
+    maxItems: 1
+    description:
+      GPIO connected to the encoder's B (phase B) output.
+
+  encoder-index-gpios:
+    maxItems: 1
+    description:
+      Optional GPIO connected to the encoder's index (Z) output.
+      The index signal pulses once per revolution and can be used
+      as a reference point for absolute position tracking.
+
+required:
+  - compatible
+  - encoder-a-gpios
+  - encoder-b-gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    quadrature-encoder {
+        compatible = "gpio-quadrature-encoder";
+        encoder-a-gpios = <&gpio0 10 GPIO_ACTIVE_LOW>;
+        encoder-b-gpios = <&gpio0 11 GPIO_ACTIVE_LOW>;
+        encoder-index-gpios = <&gpio0 12 GPIO_ACTIVE_LOW>;
+    };
+
+...
Signature · 1 line
2.52.0
Acked-by on v2 1/3
#2 lore raw

Re: [PATCH v2 1/3] dt-bindings: counter: add gpio-quadrature-encoder binding

Quoted 9 lines · Wadim Mueller

Add devicetree binding documentation for the GPIO-based quadrature encoder counter driver. The driver reads A/B quadrature signals and an optional index pulse via edge-triggered GPIO interrupts, supporting X1, X2, X4 quadrature decoding and pulse-direction mode.

This is useful on SoCs that lack a dedicated hardware quadrature decoder or where the encoder is wired to generic GPIO pins.

Signed-off-by Wadim Mueller <[email protected]>
Acked-by Conor Dooley <[email protected]>

pw-bot: not-applicable

author
#3 lore raw

PATCH v2 2/3 counter: add GPIO-based quadrature encoder driver

In reply to Wadim Mueller

Add a platform driver that turns ordinary GPIOs into a quadrature encoder counter device. The driver requests edge-triggered interrupts on the A and B (and optional Index) GPIOs and decodes the quadrature signal in software using a classic state-table approach.

Supported counting modes:
- Quadrature X1 (count on A rising edge only)
- Quadrature X2 (count on both A edges)
- Quadrature X4 (count on every A and B edge)
- Pulse-direction (A = pulse, B = direction)

An optional index signal resets the count to zero on its rising edge when enabled through sysfs. A configurable ceiling clamps the count to [0, ceiling].

Signed-off-by Wadim Mueller <[email protected]>
---
 drivers/counter/Kconfig                   |  15 +
 drivers/counter/Makefile                  |   1 +
 drivers/counter/gpio-quadrature-encoder.c | 710 ++++++++++++++++++++++
 3 files changed, 726 insertions(+)
 create mode 100644 drivers/counter/gpio-quadrature-encoder.c
drivers/counter/Kconfig +15 -0
index d30d22dfe..72c5c8159 100644
@@ -68,6 +68,21 @@ config INTEL_QEP
 	  To compile this driver as a module, choose M here: the module
 	  will be called intel-qep.
 
+config GPIO_QUADRATURE_ENCODER
+	tristate "GPIO-based quadrature encoder counter driver"
+	depends on GPIOLIB
+	help
+	  Select this option to enable the GPIO-based quadrature encoder
+	  counter driver.  It reads A/B quadrature signals and an optional
+	  index pulse via edge-triggered GPIO interrupts, supporting X1, X2,
+	  X4 quadrature decoding and pulse-direction mode.
+
+	  This is useful on SoCs that lack a dedicated hardware quadrature
+	  decoder or where the encoder is wired to generic GPIO pins.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called gpio-quadrature-encoder.
+
 config INTERRUPT_CNT
 	tristate "Interrupt counter driver"
 	depends on GPIOLIB
drivers/counter/Makefile +1 -0
index fa3c1d08f..2bef64d10 100644
@@ -14,6 +14,7 @@ obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o
 obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
 obj-$(CONFIG_TI_EQEP)		+= ti-eqep.o
 obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o
+obj-$(CONFIG_GPIO_QUADRATURE_ENCODER)	+= gpio-quadrature-encoder.o
 obj-$(CONFIG_MICROCHIP_TCB_CAPTURE)	+= microchip-tcb-capture.o
 obj-$(CONFIG_INTEL_QEP)		+= intel-qep.o
 obj-$(CONFIG_TI_ECAP_CAPTURE)	+= ti-ecap-capture.o
drivers/counter/gpio-quadrature-encoder.c new file +710 -0

710 lines not on this page · raw message

Signature · 1 line
2.52.0
author
#4 lore raw

PATCH v2 3/3 MAINTAINERS: add entry for GPIO quadrature encoder counter driver

In reply to Wadim Mueller

Add myself as maintainer for the new gpio-quadrature-encoder counter driver and its devicetree binding.

Signed-off-by Wadim Mueller <[email protected]>
---
 MAINTAINERS | 7 +++++++
 1 file changed, 7 insertions(+)
MAINTAINERS +7 -0
index 06a8c7457..fca62baa7 100644
@@ -11018,6 +11018,13 @@ F:	Documentation/dev-tools/gpio-sloppy-logic-analyzer.rst
 F:	drivers/gpio/gpio-sloppy-logic-analyzer.c
 F:	tools/gpio/gpio-sloppy-logic-analyzer.sh
 
+GPIO QUADRATURE ENCODER COUNTER DRIVER
+M:	Wadim Mueller <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	Documentation/devicetree/bindings/counter/gpio-quadrature-encoder.yaml
+F:	drivers/counter/gpio-quadrature-encoder.c
+
 GPIO SUBSYSTEM
 M:	Linus Walleij <[email protected]>
 M:	Bartosz Golaszewski <[email protected]>
Signature · 1 line
2.52.0