[PATCH 1/2] dt-bindings: HID: i2c-hid: elan: Introduce bindings for Elan eKTH6915

[PATCH 1/2] dt-bindings: HID: i2c-hid: elan: Introduce bindings for Elan eKTH6915

[Douglas Anderson]

Like many i2c-hid touchscreen controllers, the Elan eKTH6915
controller has a reset gpio. For the Goodix GT7375P touchscreen the
decision was to add a new binding rather than trying to add a new GPIO
to the existing i2c-hid binding. We'll follow the lead and do it here,
too.

SIDE NOTE: the Elan eKTH6915 is a touchscreen _controller_ that's
included as a part on some touchscreens. The reset line isn't truly
necessary for the functioning of the touchscreen, so it's possible
that some designs won't have it hooked up and will just guarantee the
power sequencing requirements with RLC circuits. Thus, we'll mark the
reset gpio as optional.

Note that if the reset GPIO isn't used there's actually no true need
to use the "elan,ekth6915" compatible instead of the "hid-over-i2c" on
Linux. However:
- Officially using just "hid-over-i2c" for this device violates the
  existing "hid-over-i2c" bindings. The bindings say that you're not
  supposed to use "post-power-on-delay-ms" without specifying a more
  specific compatible. Currently the Linux driver doesn't enforce
  this, but it violates the bindings to just use
  "hid-over-i2c". ...and if you're going to add a more specific
  compatible anyway, might as well do it right.
- Using this compatible means we don't need to specify
  "hid-descr-addr" since it's inferred from the compatible.
- Using this compatible means that the regulator names match the names
  on the Elan datasheet (vcc33 / vccio) vs the generic hid-over-i2c
  (vdd / vddl).

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 .../bindings/input/elan,ekth6915.yaml         | 65 +++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/input/elan,ekth6915.yaml

diff --git a/Documentation/devicetree/bindings/input/elan,ekth6915.yaml b/Documentation/devicetree/bindings/input/elan,ekth6915.yaml
new file mode 100644
index 000000000000..05e6f2df604c
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/elan,ekth6915.yaml
@@ -0,0 +1,65 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/elan,ekth6915.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Elan eKTH6915 touchscreen controller
+
+maintainers:
+  - Douglas Anderson <dianders@chromium.org>
+
+description:
+  Supports the Elan eKTH6915 touchscreen controller.
+  This touchscreen controller uses the i2c-hid protocol with a reset GPIO.
+
+properties:
+  compatible:
+    items:
+      - const: elan,ekth6915
+
+  reg:
+    const: 0x10
+
+  interrupts:
+    maxItems: 1
+
+  reset-gpios:
+    description: Reset GPIO; not all touchscreens using eKTH6915 hook this up.
+
+  vcc33-supply:
+    description: The 3.3V supply to the touchscreen.
+
+  vccio-supply:
+    description:
+      The IO supply to the touchscreen. Need not be specified if this is the
+      same as the 3.3V supply.
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - vcc33-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      ap_ts: touchscreen@10 {
+        compatible = "elan,ekth6915";
+        reg = <0x10>;
+
+        interrupt-parent = <&tlmm>;
+        interrupts = <9 IRQ_TYPE_LEVEL_LOW>;
+
+        reset-gpios = <&tlmm 8 GPIO_ACTIVE_LOW>;
+        vcc33-supply = <&pp3300_ts>;
+      };
+    };
-- 
2.36.1.124.g0e6072fb45-goog

[PATCH 2/2] HID: i2c-hid: elan: Add support for Elan eKTH6915 i2c-hid touchscreens

[Douglas Anderson]

Like many i2c-hid touchscreen controllers, the Elan eKTH6915 has a
reset GPIO hooked up to it. According to the datasheet, the way we're
supposed to turn the touchscreen on is:

1. Turn on the 3.3V supply.
2. Turn on the IO supply. It's OK if this is hardwired to the 3.3V
   supply, but if it's not then it must be turned on _after_ the 3.3V
   supply.
3. Wait >= 1 ms.
4. Deassert the reset GPIO (reset GPIO is active low, so there would
   be a leakage path if this was deasserted _before_ the IO supply).
5. Wait 300 ms.

Much of the above can be handled by the generic i2c-hid-of driver, but
the "reset" GPIO is not supported by that driver. Thus we'll do the
same as we did for Goodix and add a new tiny driver that uses the
i2c-hid core.

NOTE: support for this new touchscreen could theorically fit into the
Goodix driver. I've made it a separate driver because the Elan driver
supports _two_ regulators and it's unclear exactly how that would fit
in with commit 18eeef46d359 ("HID: i2c-hid: goodix: Tie the reset line
to true state of the regulator").

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 drivers/hid/i2c-hid/Kconfig           |  15 +++
 drivers/hid/i2c-hid/Makefile          |   1 +
 drivers/hid/i2c-hid/i2c-hid-of-elan.c | 127 ++++++++++++++++++++++++++
 3 files changed, 143 insertions(+)
 create mode 100644 drivers/hid/i2c-hid/i2c-hid-of-elan.c

diff --git a/drivers/hid/i2c-hid/Kconfig b/drivers/hid/i2c-hid/Kconfig
index a16c6a69680b..5273ee2bb134 100644
--- a/drivers/hid/i2c-hid/Kconfig
+++ b/drivers/hid/i2c-hid/Kconfig
@@ -32,6 +32,21 @@ config I2C_HID_OF
 	  will be called i2c-hid-of.  It will also build/depend on the
 	  module i2c-hid.
 
+config I2C_HID_OF_ELAN
+	tristate "Driver for Elan hid-i2c based devices on OF systems"
+	default n
+	depends on I2C && INPUT && OF
+	help
+	  Say Y here if you want support for Elan i2c devices that use
+	  the i2c-hid protocol on Open Firmware (Device Tree)-based
+	  systems.
+
+	  If unsure, say N.
+
+	  This support is also available as a module.  If so, the module
+	  will be called i2c-hid-of-elan.  It will also build/depend on
+	  the module i2c-hid.
+
 config I2C_HID_OF_GOODIX
 	tristate "Driver for Goodix hid-i2c based devices on OF systems"
 	default n
diff --git a/drivers/hid/i2c-hid/Makefile b/drivers/hid/i2c-hid/Makefile
index 302545a771f3..55bd5e0f35af 100644
--- a/drivers/hid/i2c-hid/Makefile
+++ b/drivers/hid/i2c-hid/Makefile
@@ -10,4 +10,5 @@ i2c-hid-$(CONFIG_DMI)				+= i2c-hid-dmi-quirks.o
 
 obj-$(CONFIG_I2C_HID_ACPI)			+= i2c-hid-acpi.o
 obj-$(CONFIG_I2C_HID_OF)			+= i2c-hid-of.o
+obj-$(CONFIG_I2C_HID_OF_ELAN)			+= i2c-hid-of-elan.o
 obj-$(CONFIG_I2C_HID_OF_GOODIX)			+= i2c-hid-of-goodix.o
diff --git a/drivers/hid/i2c-hid/i2c-hid-of-elan.c b/drivers/hid/i2c-hid/i2c-hid-of-elan.c
new file mode 100644
index 000000000000..e2b3456e97b5
--- /dev/null
+++ b/drivers/hid/i2c-hid/i2c-hid-of-elan.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for Elan touchscreens that use the i2c-hid protocol.
+ *
+ * Copyright 2020 Google LLC
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pm.h>
+#include <linux/regulator/consumer.h>
+
+#include "i2c-hid.h"
+
+struct elan_i2c_hid_timing_data {
+	unsigned int post_gpio_reset_delay_ms;
+	unsigned int post_power_delay_ms;
+};
+
+struct i2c_hid_of_elan {
+	struct i2chid_ops ops;
+
+	struct regulator *vcc33;
+	struct regulator *vccio;
+	struct gpio_desc *reset_gpio;
+	const struct elan_i2c_hid_timing_data *timings;
+};
+
+static int elan_i2c_hid_power_up(struct i2chid_ops *ops)
+{
+	struct i2c_hid_of_elan *ihid_elan =
+		container_of(ops, struct i2c_hid_of_elan, ops);
+	int ret;
+
+	ret = regulator_enable(ihid_elan->vcc33);
+	if (ret)
+		return ret;
+
+	ret = regulator_enable(ihid_elan->vccio);
+	if (ret) {
+		regulator_disable(ihid_elan->vcc33);
+		return ret;
+	}
+
+	if (ihid_elan->timings->post_power_delay_ms)
+		msleep(ihid_elan->timings->post_power_delay_ms);
+
+	gpiod_set_value_cansleep(ihid_elan->reset_gpio, 0);
+	if (ihid_elan->timings->post_gpio_reset_delay_ms)
+		msleep(ihid_elan->timings->post_gpio_reset_delay_ms);
+
+	return 0;
+}
+
+static void elan_i2c_hid_power_down(struct i2chid_ops *ops)
+{
+	struct i2c_hid_of_elan *ihid_elan =
+		container_of(ops, struct i2c_hid_of_elan, ops);
+
+	gpiod_set_value_cansleep(ihid_elan->reset_gpio, 1);
+	regulator_disable(ihid_elan->vccio);
+	regulator_disable(ihid_elan->vcc33);
+}
+
+static int i2c_hid_of_elan_probe(struct i2c_client *client,
+				   const struct i2c_device_id *id)
+{
+	struct i2c_hid_of_elan *ihid_elan;
+
+	ihid_elan = devm_kzalloc(&client->dev, sizeof(*ihid_elan), GFP_KERNEL);
+	if (!ihid_elan)
+		return -ENOMEM;
+
+	ihid_elan->ops.power_up = elan_i2c_hid_power_up;
+	ihid_elan->ops.power_down = elan_i2c_hid_power_down;
+
+	/* Start out with reset asserted */
+	ihid_elan->reset_gpio =
+		devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(ihid_elan->reset_gpio))
+		return PTR_ERR(ihid_elan->reset_gpio);
+
+	ihid_elan->vccio = devm_regulator_get(&client->dev, "vccio");
+	if (IS_ERR(ihid_elan->vccio))
+		return PTR_ERR(ihid_elan->vccio);
+
+	ihid_elan->vcc33 = devm_regulator_get(&client->dev, "vcc33");
+	if (IS_ERR(ihid_elan->vcc33))
+		return PTR_ERR(ihid_elan->vcc33);
+
+	ihid_elan->timings = device_get_match_data(&client->dev);
+
+	return i2c_hid_core_probe(client, &ihid_elan->ops, 0x0001, 0);
+}
+
+static const struct elan_i2c_hid_timing_data elan_ekth6915_timing_data = {
+	.post_power_delay_ms = 1,
+	.post_gpio_reset_delay_ms = 300,
+};
+
+static const struct of_device_id elan_i2c_hid_of_match[] = {
+	{ .compatible = "elan,ekth6915", .data = &elan_ekth6915_timing_data },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, elan_i2c_hid_of_match);
+
+static struct i2c_driver elan_i2c_hid_ts_driver = {
+	.driver = {
+		.name	= "i2c_hid_of_elan",
+		.pm	= &i2c_hid_core_pm,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = of_match_ptr(elan_i2c_hid_of_match),
+	},
+	.probe		= i2c_hid_of_elan_probe,
+	.remove		= i2c_hid_core_remove,
+	.shutdown	= i2c_hid_core_shutdown,
+};
+module_i2c_driver(elan_i2c_hid_ts_driver);
+
+MODULE_AUTHOR("Douglas Anderson <dianders@chromium.org>");
+MODULE_DESCRIPTION("Elan i2c-hid touchscreen driver");
+MODULE_LICENSE("GPL");
-- 
2.36.1.124.g0e6072fb45-goog

Re: [PATCH 2/2] HID: i2c-hid: elan: Add support for Elan eKTH6915 i2c-hid touchscreens

[Dmitry Torokhov]

On Thu, May 19, 2022 at 04:00:03PM -0700, Douglas Anderson wrote:
> Like many i2c-hid touchscreen controllers, the Elan eKTH6915 has a
> reset GPIO hooked up to it. According to the datasheet, the way we're
> supposed to turn the touchscreen on is:
> 
> 1. Turn on the 3.3V supply.
> 2. Turn on the IO supply. It's OK if this is hardwired to the 3.3V
>    supply, but if it's not then it must be turned on _after_ the 3.3V
>    supply.
> 3. Wait >= 1 ms.
> 4. Deassert the reset GPIO (reset GPIO is active low, so there would
>    be a leakage path if this was deasserted _before_ the IO supply).
> 5. Wait 300 ms.
> 
> Much of the above can be handled by the generic i2c-hid-of driver, but
> the "reset" GPIO is not supported by that driver. Thus we'll do the
> same as we did for Goodix and add a new tiny driver that uses the
> i2c-hid core.
> 
> NOTE: support for this new touchscreen could theorically fit into the
> Goodix driver. I've made it a separate driver because the Elan driver
> supports _two_ regulators and it's unclear exactly how that would fit
> in with commit 18eeef46d359 ("HID: i2c-hid: goodix: Tie the reset line
> to true state of the regulator").
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

> +
> +	return i2c_hid_core_probe(client, &ihid_elan->ops, 0x0001, 0);

Maybe #define for the descriptor address, or rename
elan_i2c_hid_timing_data into elan_i2c_hid_chip_data and put it there?

Thanks.

-- 
Dmitry

Re: [PATCH 1/2] dt-bindings: HID: i2c-hid: elan: Introduce bindings for Elan eKTH6915

[Dmitry Torokhov]

On Thu, May 19, 2022 at 04:00:02PM -0700, Douglas Anderson wrote:
> Like many i2c-hid touchscreen controllers, the Elan eKTH6915
> controller has a reset gpio. For the Goodix GT7375P touchscreen the
> decision was to add a new binding rather than trying to add a new GPIO
> to the existing i2c-hid binding. We'll follow the lead and do it here,
> too.
> 
> SIDE NOTE: the Elan eKTH6915 is a touchscreen _controller_ that's
> included as a part on some touchscreens. The reset line isn't truly
> necessary for the functioning of the touchscreen, so it's possible
> that some designs won't have it hooked up and will just guarantee the
> power sequencing requirements with RLC circuits. Thus, we'll mark the
> reset gpio as optional.
> 
> Note that if the reset GPIO isn't used there's actually no true need
> to use the "elan,ekth6915" compatible instead of the "hid-over-i2c" on
> Linux. However:
> - Officially using just "hid-over-i2c" for this device violates the
>   existing "hid-over-i2c" bindings. The bindings say that you're not
>   supposed to use "post-power-on-delay-ms" without specifying a more
>   specific compatible. Currently the Linux driver doesn't enforce
>   this, but it violates the bindings to just use
>   "hid-over-i2c". ...and if you're going to add a more specific
>   compatible anyway, might as well do it right.
> - Using this compatible means we don't need to specify
>   "hid-descr-addr" since it's inferred from the compatible.
> - Using this compatible means that the regulator names match the names
>   on the Elan datasheet (vcc33 / vccio) vs the generic hid-over-i2c
>   (vdd / vddl).
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Thanks.

-- 
Dmitry