[PATCH v4 0/5] add z1 and z2 channels support for resistive-adc-touch driver

[PATCH v4 0/5] add z1 and z2 channels support for resistive-adc-touch driver

[Oleksij Rempel]

changes v4:
- resistive-adc-touch: remove unused variable

changes v3:
- yaml: fix validation for channel names
- yaml: add nodename validation

changes v2:
- add yaml conversion patch to this series
- reword commit message for the last patch
- fix possible overflow on the buffer dispatcher

Oleksij Rempel (5):
  dt-bindings: touchscreen: validate nodename
  dt-bindings: touchscreen: Convert resistive-adc-touch binding to json
    schema
  dt-bindings: touchscreen: add touchscreen-x/y-plate-ohms property
  dt-bindings: touchscreen: resistive-adc-touch: add support for z1 and
    z2 channels
  Input: resistive-adc-touch: add support for z1 and z2 channels

 .../input/touchscreen/resistive-adc-touch.txt |  33 ----
 .../touchscreen/resistive-adc-touch.yaml      |  86 +++++++++++
 .../input/touchscreen/touchscreen.yaml        |   9 ++
 .../input/touchscreen/resistive-adc-touch.c   | 142 ++++++++++++++++--
 4 files changed, 223 insertions(+), 47 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.txt
 create mode 100644 Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.yaml

-- 
2.29.2

[PATCH v4 1/5] dt-bindings: touchscreen: validate nodename

[Oleksij Rempel]

Validate touchscreen nodes. Make sure it is named touchscreen*.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 .../devicetree/bindings/input/touchscreen/touchscreen.yaml     | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml
index 046ace461cc9..057e1063759c 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml
+++ b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml
@@ -10,6 +10,9 @@ maintainers:
   - Dmitry Torokhov <dmitry.torokhov@gmail.com>
 
 properties:
+  $nodename:
+    pattern: "^touchscreen(@.*)?$"
+
   touchscreen-min-x:
     description: minimum x coordinate reported
     $ref: /schemas/types.yaml#/definitions/uint32
-- 
2.29.2

Re: [PATCH v4 1/5] dt-bindings: touchscreen: validate nodename

[Rob Herring]

On Wed, 19 May 2021 11:42:17 +0200, Oleksij Rempel wrote:
> Validate touchscreen nodes. Make sure it is named touchscreen*.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  .../devicetree/bindings/input/touchscreen/touchscreen.yaml     | 3 +++
>  1 file changed, 3 insertions(+)
> 

My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
on your patch (DT_CHECKER_FLAGS is new in v5.13):

yamllint warnings/errors:

dtschema/dtc warnings/errors:
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.example.dt.yaml: edt-ft5x06@38: $nodename:0: 'edt-ft5x06@38' does not match '^touchscreen(@.*)?$'
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/input/touchscreen/edt-ft5x06.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/input/touchscreen/goodix.example.dt.yaml: gt928@5d: $nodename:0: 'gt928@5d' does not match '^touchscreen(@.*)?$'
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/input/touchscreen/goodix.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/input/iqs626a.example.dt.yaml: iqs626a@44: $nodename:0: 'iqs626a@44' does not match '^touchscreen(@.*)?$'
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/input/iqs626a.yaml

See https://patchwork.ozlabs.org/patch/1480791

This check can fail if there are any dependencies. The base for a patch
series is generally the most recent rc1.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit.

[PATCH v4 2/5] dt-bindings: touchscreen: Convert resistive-adc-touch binding to json schema

[Oleksij Rempel]

Convert the resistive-adc-touch binding to DT schema format using json-schema.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 .../input/touchscreen/resistive-adc-touch.txt | 33 ---------
 .../touchscreen/resistive-adc-touch.yaml      | 70 +++++++++++++++++++
 2 files changed, 70 insertions(+), 33 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.txt
 create mode 100644 Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.yaml

diff --git a/Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.txt b/Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.txt
deleted file mode 100644
index af5223bb5bdd..000000000000
--- a/Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.txt
+++ /dev/null
@@ -1,33 +0,0 @@
-Generic resistive touchscreen ADC
-
-Required properties:
-
- - compatible: must be "resistive-adc-touch"
-The device must be connected to an ADC device that provides channels for
-position measurement and optional pressure.
-Refer to
-https://github.com/devicetree-org/dt-schema/blob/master/schemas/iio/iio-consumer.yaml
-for details
-
- - iio-channels: must have at least two channels connected to an ADC device.
-These should correspond to the channels exposed by the ADC device and should
-have the right index as the ADC device registers them. These channels
-represent the relative position on the "x" and "y" axes.
- - iio-channel-names: must have all the channels' names. Mandatory channels
-are "x" and "y".
-
-Optional properties:
- - iio-channels: The third channel named "pressure" is optional and can be
-used if the ADC device also measures pressure besides position.
-If this channel is missing, pressure will be ignored and the touchscreen
-will only report position.
- - iio-channel-names: optional channel named "pressure".
-
-Example:
-
-	resistive_touch: resistive_touch {
-		compatible = "resistive-adc-touch";
-		touchscreen-min-pressure = <50000>;
-		io-channels = <&adc 24>, <&adc 25>, <&adc 26>;
-		io-channel-names = "x", "y", "pressure";
-	};
diff --git a/Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.yaml b/Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.yaml
new file mode 100644
index 000000000000..38b4cbee9429
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.yaml
@@ -0,0 +1,70 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/touchscreen/resistive-adc-touch.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic resistive touchscreen ADC
+
+maintainers:
+  - Oleksij Rempel <o.rempel@pengutronix.de>
+
+description: |
+  Generic ADC based resistive touchscreen controller
+  The device must be connected to an ADC device that provides channels for
+  position measurement and optional pressure.
+
+allOf:
+  - $ref: touchscreen.yaml#
+
+properties:
+  compatible:
+    const: resistive-adc-touch
+
+  io-channels:
+    minItems: 2
+    items:
+      - description: x
+      - description: y
+      - description: pressure (optional)
+
+  io-channel-names:
+    oneOf:
+      - items:
+          - enum: [x, y]
+          - enum: [x, y]
+      - items:
+          - enum: [x, y, pressure]
+          - enum: [x, y, pressure]
+          - enum: [x, y, pressure]
+
+  touchscreen-size-x: true
+  touchscreen-size-y: true
+  touchscreen-fuzz-x: true
+  touchscreen-fuzz-y: true
+  touchscreen-inverted-x: true
+  touchscreen-inverted-y: true
+  touchscreen-swapped-x-y: true
+  touchscreen-min-pressure: true
+
+additionalProperties: false
+
+required:
+  - compatible
+  - io-channels
+  - io-channel-names
+
+examples:
+  - |
+    touchscreen {
+      compatible = "resistive-adc-touch";
+      io-channels = <&adc 24>, <&adc 25>;
+      io-channel-names = "y", "x";
+    };
+  - |
+    touchscreen {
+      compatible = "resistive-adc-touch";
+      touchscreen-min-pressure = <50000>;
+      io-channels = <&adc 24>, <&adc 25>, <&adc 26>;
+      io-channel-names = "y", "pressure", "x";
+    };
-- 
2.29.2

Re: [PATCH v4 2/5] dt-bindings: touchscreen: Convert resistive-adc-touch binding to json schema

[Rob Herring]

On Wed, 19 May 2021 11:42:18 +0200, Oleksij Rempel wrote:
> Convert the resistive-adc-touch binding to DT schema format using json-schema.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  .../input/touchscreen/resistive-adc-touch.txt | 33 ---------
>  .../touchscreen/resistive-adc-touch.yaml      | 70 +++++++++++++++++++
>  2 files changed, 70 insertions(+), 33 deletions(-)
>  delete mode 100644 Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.txt
>  create mode 100644 Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.yaml
> 

Reviewed-by: Rob Herring <robh@kernel.org>

[PATCH v4 3/5] dt-bindings: touchscreen: add touchscreen-x/y-plate-ohms property

[Oleksij Rempel]

Te calculate the pressure on a restrictive touchscreen we need need to
know resistance at least of X plate. Some calculations need to use both
X and Y values.
So, add generic properties which can be used by all drivers

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 .../devicetree/bindings/input/touchscreen/touchscreen.yaml  | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml
index 057e1063759c..2d7b039ce47f 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml
+++ b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml
@@ -77,6 +77,12 @@ properties:
   touchscreen-y-mm:
     description: vertical length in mm of the touchscreen
 
+  touchscreen-x-plate-ohms:
+    description: Resistance of the X-plate in Ohms
+
+  touchscreen-y-plate-ohms:
+    description: Resistance of the Y-plate in Ohms
+
 dependencies:
   touchscreen-size-x: [ touchscreen-size-y ]
   touchscreen-size-y: [ touchscreen-size-x ]
-- 
2.29.2

Re: [PATCH v4 3/5] dt-bindings: touchscreen: add touchscreen-x/y-plate-ohms property

[Rob Herring]

On Wed, 19 May 2021 11:42:19 +0200, Oleksij Rempel wrote:
> Te calculate the pressure on a restrictive touchscreen we need need to
> know resistance at least of X plate. Some calculations need to use both
> X and Y values.
> So, add generic properties which can be used by all drivers
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  .../devicetree/bindings/input/touchscreen/touchscreen.yaml  | 6 ++++++
>  1 file changed, 6 insertions(+)
> 

Reviewed-by: Rob Herring <robh@kernel.org>

[PATCH v4 4/5] dt-bindings: touchscreen: resistive-adc-touch: add support for z1 and z2 channels

[Oleksij Rempel]

For pressure calculation based on plates resistance we need some additional
properties:
- z1 and z2 channels with additional measurements between plates
- actual resistance of the touchscreen. Currently we use only
  X-resistance.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 .../input/touchscreen/resistive-adc-touch.yaml   | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.yaml b/Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.yaml
index 38b4cbee9429..7fc22a403d48 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.yaml
+++ b/Documentation/devicetree/bindings/input/touchscreen/resistive-adc-touch.yaml
@@ -27,6 +27,8 @@ properties:
       - description: x
       - description: y
       - description: pressure (optional)
+      - description: z1 (optional)
+      - description: z2 (optional)
 
   io-channel-names:
     oneOf:
@@ -37,6 +39,11 @@ properties:
           - enum: [x, y, pressure]
           - enum: [x, y, pressure]
           - enum: [x, y, pressure]
+      - items:
+          - enum: [x, y, z1, z2]
+          - enum: [x, y, z1, z2]
+          - enum: [x, y, z1, z2]
+          - enum: [x, y, z1, z2]
 
   touchscreen-size-x: true
   touchscreen-size-y: true
@@ -46,6 +53,7 @@ properties:
   touchscreen-inverted-y: true
   touchscreen-swapped-x-y: true
   touchscreen-min-pressure: true
+  touchscreen-x-plate-ohms: true
 
 additionalProperties: false
 
@@ -68,3 +76,11 @@ examples:
       io-channels = <&adc 24>, <&adc 25>, <&adc 26>;
       io-channel-names = "y", "pressure", "x";
     };
+  - |
+    touchscreen {
+      compatible = "resistive-adc-touch";
+      touchscreen-min-pressure = <50000>;
+      io-channels = <&adc 1>, <&adc 2>, <&adc 3>, <&adc 4>;
+      io-channel-names = "x", "z1", "z2", "y";
+      touchscreen-x-plate-ohms = <800>;
+    };
-- 
2.29.2

Re: [PATCH v4 4/5] dt-bindings: touchscreen: resistive-adc-touch: add support for z1 and z2 channels

[Rob Herring]

On Wed, 19 May 2021 11:42:20 +0200, Oleksij Rempel wrote:
> For pressure calculation based on plates resistance we need some additional
> properties:
> - z1 and z2 channels with additional measurements between plates
> - actual resistance of the touchscreen. Currently we use only
>   X-resistance.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  .../input/touchscreen/resistive-adc-touch.yaml   | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 

Reviewed-by: Rob Herring <robh@kernel.org>

[PATCH v4 5/5] Input: resistive-adc-touch: add support for z1 and z2 channels

[Oleksij Rempel]

This patch adds support for the z1 and z2 channels. These are used to
calculate the applied pressure. As there is no common order of the
individual channels of a resistive touch ADC, support for
io-channel-names is added (although the DT bindings stated the
driver already supports these).

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 .../input/touchscreen/resistive-adc-touch.c   | 142 ++++++++++++++++--
 1 file changed, 128 insertions(+), 14 deletions(-)

diff --git a/drivers/input/touchscreen/resistive-adc-touch.c b/drivers/input/touchscreen/resistive-adc-touch.c
index e50af30183f4..fa90005b7bc9 100644
--- a/drivers/input/touchscreen/resistive-adc-touch.c
+++ b/drivers/input/touchscreen/resistive-adc-touch.c
@@ -20,7 +20,18 @@
 
 #define DRIVER_NAME					"resistive-adc-touch"
 #define GRTS_DEFAULT_PRESSURE_MIN			50000
+#define GRTS_DEFAULT_PRESSURE_MAX			65535
 #define GRTS_MAX_POS_MASK				GENMASK(11, 0)
+#define GRTS_MAX_CHANNELS				4
+
+enum grts_ch_type {
+	GRTS_CH_NONE = 0,
+	GRTS_CH_X,
+	GRTS_CH_Y,
+	GRTS_CH_PRESSURE,
+	GRTS_CH_Z1,
+	GRTS_CH_Z2,
+};
 
 /**
  * struct grts_state - generic resistive touch screen information struct
@@ -33,24 +44,61 @@
  */
 struct grts_state {
 	u32				pressure_min;
+	u32				x_plate_ohms;
 	bool				pressure;
 	struct iio_channel		*iio_chans;
 	struct iio_cb_buffer		*iio_cb;
 	struct input_dev		*input;
 	struct touchscreen_properties	prop;
+	u8				ch[GRTS_MAX_CHANNELS];
 };
 
 static int grts_cb(const void *data, void *private)
 {
 	const u16 *touch_info = data;
 	struct grts_state *st = private;
-	unsigned int x, y, press = 0x0;
+	unsigned int x, y, press = 0, z1 = 0, z2;
+	unsigned int Rt, i;
+
+	for (i = 0; i < ARRAY_SIZE(st->ch) && st->ch[i] != GRTS_CH_NONE; i++) {
+		switch (st->ch[i]) {
+		case GRTS_CH_X:
+			x = touch_info[i];
+			break;
+		case GRTS_CH_Y:
+			y = touch_info[i];
+			break;
+		case GRTS_CH_PRESSURE:
+			press = touch_info[i];
+			break;
+		case GRTS_CH_Z1:
+			z1 = touch_info[i];
+			break;
+		case GRTS_CH_Z2:
+			z2 = touch_info[i];
+			break;
+		case GRTS_CH_NONE:
+			break;
+		}
+	}
 
-	/* channel data coming in buffer in the order below */
-	x = touch_info[0];
-	y = touch_info[1];
-	if (st->pressure)
-		press = touch_info[2];
+	if (z1) {
+		Rt = z2;
+		Rt -= z1;
+		Rt *= st->x_plate_ohms;
+		Rt = DIV_ROUND_CLOSEST(Rt, 16);
+		Rt *= x;
+		Rt /= z1;
+		Rt = DIV_ROUND_CLOSEST(Rt, 256);
+		/*
+		 * On increased pressure the resistance (Rt) is decreasing
+		 * so, convert values to make it looks as real pressure.
+		 */
+		if (Rt < GRTS_DEFAULT_PRESSURE_MAX)
+			press = GRTS_DEFAULT_PRESSURE_MAX - Rt;
+		else
+			press = 0;
+	}
 
 	if ((!x && !y) || (st->pressure && (press < st->pressure_min))) {
 		/* report end of touch */
@@ -94,12 +142,77 @@ static void grts_disable(void *data)
 	iio_channel_release_all_cb(data);
 }
 
+static int grts_get_properties(struct grts_state *st, struct device *dev)
+{
+	int idx, error;
+
+	idx = device_property_match_string(dev, "io-channel-names", "x");
+	if (idx < 0)
+		return idx;
+
+	if (idx >= ARRAY_SIZE(st->ch))
+		return -EOVERFLOW;
+
+	st->ch[idx] = GRTS_CH_X;
+
+	idx = device_property_match_string(dev, "io-channel-names", "y");
+	if (idx < 0)
+		return idx;
+
+	if (idx >= ARRAY_SIZE(st->ch))
+		return -EOVERFLOW;
+
+	st->ch[idx] = GRTS_CH_Y;
+
+	/* pressure is optional */
+	idx = device_property_match_string(dev, "io-channel-names", "pressure");
+	if (idx >= 0) {
+		if (idx >= ARRAY_SIZE(st->ch))
+			return -EOVERFLOW;
+
+		st->ch[idx] = GRTS_CH_PRESSURE;
+		st->pressure = true;
+
+		return 0;
+	}
+
+	/* if no pressure is defined, try optional z1 + z2 */
+	idx = device_property_match_string(dev, "io-channel-names", "z1");
+	if (idx < 0)
+		return 0;
+
+	if (idx >= ARRAY_SIZE(st->ch))
+		return -EOVERFLOW;
+
+	st->ch[idx] = GRTS_CH_Z1;
+
+	/* if z1 is provided z2 is not optional */
+	idx = device_property_match_string(dev, "io-channel-names", "z2");
+	if (idx < 0)
+		return idx;
+
+	if (idx >= ARRAY_SIZE(st->ch))
+		return -EOVERFLOW;
+
+	st->ch[idx] = GRTS_CH_Z2;
+	st->pressure = true;
+
+	error = device_property_read_u32(dev,
+					 "touchscreen-x-plate-ohms",
+					 &st->x_plate_ohms);
+	if (error) {
+		dev_err(dev, "can't get touchscreen-x-plate-ohms property\n");
+		return error;
+	}
+
+	return 0;
+}
+
 static int grts_probe(struct platform_device *pdev)
 {
 	struct grts_state *st;
 	struct input_dev *input;
 	struct device *dev = &pdev->dev;
-	struct iio_channel *chan;
 	int error;
 
 	st = devm_kzalloc(dev, sizeof(struct grts_state), GFP_KERNEL);
@@ -115,12 +228,13 @@ static int grts_probe(struct platform_device *pdev)
 		return error;
 	}
 
-	chan = &st->iio_chans[0];
-	st->pressure = false;
-	while (chan && chan->indio_dev) {
-		if (!strcmp(chan->channel->datasheet_name, "pressure"))
-			st->pressure = true;
-		chan++;
+	if (!device_property_present(dev, "io-channel-names"))
+		return -ENODEV;
+
+	error = grts_get_properties(st, dev);
+	if (error) {
+		dev_err(dev, "Failed to parse properties\n");
+		return error;
 	}
 
 	if (st->pressure) {
@@ -148,7 +262,7 @@ static int grts_probe(struct platform_device *pdev)
 	input_set_abs_params(input, ABS_Y, 0, GRTS_MAX_POS_MASK - 1, 0, 0);
 	if (st->pressure)
 		input_set_abs_params(input, ABS_PRESSURE, st->pressure_min,
-				     0xffff, 0, 0);
+				     GRTS_DEFAULT_PRESSURE_MAX, 0, 0);
 
 	input_set_capability(input, EV_KEY, BTN_TOUCH);
 
-- 
2.29.2