Hi Fei,
On Tue, Apr 18, 2023 at 08:49:52PM +0800, Fei Shao wrote:
> 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;
> + }
Please let me know in case I have misunderstood, but I don't see a need
to change the regulator_enable/disable() logic if this property is set.
If the regulators are truly always-on, the regulator core already knows
what to do and we should not duplicate that logic here.
Based on the alleged silicon erratum discussed in patch [1/2], it seems
we only want to control the behavior of the reset GPIO. Therefore, only
the calls to gpiod_set_value_cansleep() should be affected and the name
of the property updated to reflect what it's actually doing.
>
> 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
>
Kind regards,
Jeff LaBundy
