[PATCH v2 2/2] HID: i2c-hid: goodix: Add support for "goodix,no-reset-during-suspend" property

[Fei Shao]

In the beginning, commit 18eeef46d359 ("HID: i2c-hid: goodix: Tie the
reset line to true state of the regulator") introduced a change to tie
the reset line of the Goodix touchscreen to the state of the regulator
to fix a power leakage issue in suspend.

After some time, the change was deemed unnecessary and was reverted in
commit 557e05fa9fdd ("HID: i2c-hid: goodix: Stop tying the reset line to
the regulator") due to difficulties in managing regulator notifiers for
designs like Evoker, which provides a second power rail to touchscreen.

However, the revert caused a power regression on another Chromebook
device Steelix in the field, which has a dedicated always-on regulator
for touchscreen and was covered by the workaround in the first commit.

To address both cases, this patch adds the support for the new
"goodix,no-reset-during-suspend" property in the driver:
- When set to true, the driver does not assert the reset GPIO during
  power-down.
  Instead, the GPIO will be asserted during power-up to ensure the
  touchscreen always has a clean start and consistent behavior after
  resuming.
  This is for designs with a dedicated always-on regulator.
- When set to false or unset, the driver uses the original control flow
  and asserts GPIO and disable regulators normally.
  This is for the two-regulator and shared-regulator designs.

Signed-off-by: Fei Shao <fshao at chromium.org>
Reviewed-by: Douglas Anderson <dianders at chromium.org>

---

Changes in v2:
- Do not change the regulator_enable logic during power-up.

 drivers/hid/i2c-hid/i2c-hid-of-goodix.c | 26 +++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/hid/i2c-hid/i2c-hid-of-goodix.c b/drivers/hid/i2c-hid/i2c-hid-of-goodix.c
index 0060e3dcd775..fc4532fcadcc 100644
--- a/drivers/hid/i2c-hid/i2c-hid-of-goodix.c
+++ b/drivers/hid/i2c-hid/i2c-hid-of-goodix.c
@@ -28,6 +28,7 @@ struct i2c_hid_of_goodix {
 	struct regulator *vdd;
 	struct regulator *vddio;
 	struct gpio_desc *reset_gpio;
+	bool no_reset_during_suspend;
 	const struct goodix_i2c_hid_timing_data *timings;
 };
 
@@ -37,6 +38,20 @@ static int goodix_i2c_hid_power_up(struct i2chid_ops *ops)
 		container_of(ops, struct i2c_hid_of_goodix, ops);
 	int ret;
 
+	if (ihid_goodix->no_reset_during_suspend) {
+		/*
+		 * This is not mandatory, but we assert reset here (instead of
+		 * during power-down) to ensure the device will have a clean
+		 * state after powering up, just like the normal scenarios will
+		 * have.
+		 *
+		 * Note that in this case we assume the regulators should be
+		 * (marked as) always-on, so the regulator core knows what to
+		 * do with them in the following regulator_enable() calls
+		 * despite regulator_disable() was not called previously.
+		 */
+		gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1);
+	}
 	ret = regulator_enable(ihid_goodix->vdd);
 	if (ret)
 		return ret;
@@ -60,6 +75,14 @@ static void goodix_i2c_hid_power_down(struct i2chid_ops *ops)
 	struct i2c_hid_of_goodix *ihid_goodix =
 		container_of(ops, struct i2c_hid_of_goodix, ops);
 
+	/*
+	 * Don't assert reset GPIO if it's set.
+	 * Also, it's okay to skip the following regulator_disable() calls
+	 * because the regulators should be always-on in this case.
+	 */
+	if (ihid_goodix->no_reset_during_suspend)
+		return;
+
 	gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1);
 	regulator_disable(ihid_goodix->vddio);
 	regulator_disable(ihid_goodix->vdd);
@@ -91,6 +114,9 @@ static int i2c_hid_of_goodix_probe(struct i2c_client *client)
 	if (IS_ERR(ihid_goodix->vddio))
 		return PTR_ERR(ihid_goodix->vddio);
 
+	ihid_goodix->no_reset_during_suspend =
+		of_property_read_bool(client->dev.of_node, "goodix,no-reset-during-suspend");
+
 	ihid_goodix->timings = device_get_match_data(&client->dev);
 
 	return i2c_hid_core_probe(client, &ihid_goodix->ops, 0x0001, 0);
-- 
2.40.1.495.gc816e09b53d-goog