[PATCH 2/2] HID: i2c-hid: goodix: Add support for powered-in-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
`powered-in-suspend` property in the driver that allows the driver to
determine whether the touchscreen is still powered in suspend, and
handle the reset GPIO accordingly as below:
- When set to true, the driver does not assert the reset GPIO in power
  down. To ensure a clean start and the consistent behavior, it does the
  assertion in power up instead.
  This is for designs with a dedicated always-on regulator.
- When set to false, 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@xxxxxxxxxxxx>

---

 drivers/hid/i2c-hid/i2c-hid-of-goodix.c | 46 +++++++++++++++++++++----
 1 file changed, 39 insertions(+), 7 deletions(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid-of-goodix.c b/drivers/hid/i2c-hid/i2c-hid-of-goodix.c
index 0060e3dcd775..b438db8ca6f4 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 powered_in_suspend;
 	const struct goodix_i2c_hid_timing_data *timings;
 };
 
@@ -37,13 +38,34 @@ static int goodix_i2c_hid_power_up(struct i2chid_ops *ops)
 		container_of(ops, struct i2c_hid_of_goodix, ops);
 	int ret;
 
-	ret = regulator_enable(ihid_goodix->vdd);
-	if (ret)
-		return ret;
-
-	ret = regulator_enable(ihid_goodix->vddio);
-	if (ret)
-		return ret;
+	/*
+	 * This is to ensure that the reset GPIO will be asserted and the
+	 * regulators will be enabled for all cases.
+	 */
+	if (ihid_goodix->powered_in_suspend) {
+		/*
+		 * This is not mandatory, but we assert reset here (instead of
+		 * in power-down) to ensure that the device will have a clean
+		 * state later on just like the normal scenarios would have.
+		 *
+		 * Also, since the regulators were not disabled in power-down,
+		 * we don't need to enable them here.
+		 */
+		gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1);
+	} else {
+		/*
+		 * In this case, the reset is already asserted (either in
+		 * probe or power-down).
+		 * All we need is to enable the regulators.
+		 */
+		ret = regulator_enable(ihid_goodix->vdd);
+		if (ret)
+			return ret;
+
+		ret = regulator_enable(ihid_goodix->vddio);
+		if (ret)
+			return ret;
+	}
 
 	if (ihid_goodix->timings->post_power_delay_ms)
 		msleep(ihid_goodix->timings->post_power_delay_ms);
@@ -60,6 +82,13 @@ 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 or disable regulators if we're keeping the
+	 * device powered in suspend.
+	 */
+	if (ihid_goodix->powered_in_suspend)
+		return;
+
 	gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1);
 	regulator_disable(ihid_goodix->vddio);
 	regulator_disable(ihid_goodix->vdd);
@@ -91,6 +120,9 @@ 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->powered_in_suspend =
+		of_property_read_bool(client->dev.of_node, "powered-in-suspend");
+
 	ihid_goodix->timings = device_get_match_data(&client->dev);
 
 	return i2c_hid_core_probe(client, &ihid_goodix->ops, 0x0001, 0);
-- 
2.40.0.634.g4ca3ef3211-goog