From 18eeef46d3593e3bc3d6a8f7a6f94ace356578ff Mon Sep 17 00:00:00 2001 From: Douglas Anderson Date: Fri, 25 Jun 2021 08:18:36 -0700 Subject: HID: i2c-hid: goodix: Tie the reset line to true state of the regulator The regulator for the touchscreen could be: * A dedicated regulator just for the touchscreen. * A regulator shared with something else in the system. * An always-on regulator. How we want the "reset" line to behave depends a bit on which of those three cases we're in. Currently the code is written with the assumption that it has a dedicated regulator, but that's not really guaranteed to be the case. The problem we run into is that if we leave the touchscreen powered on (because someone else is requesting the regulator or it's an always-on regulator) and we assert reset then we apparently burn an extra 67 mW of power. That's not great. Let's instead tie the control of the reset line to the true state of the regulator as reported by regulator notifiers. If we have an always-on regulator our notifier will never be called. If we have a shared regulator then our notifier will be called when the touchscreen is truly turned on or truly turned off. Using notifiers like this nicely handles all the cases without resorting to hacks like pretending that there is no "reset" GPIO if we have an always-on regulator. NOTE: if the regulator is on a shared line it's still possible that things could be a little off. Specifically, this case is not handled even after this patch: 1. Suspend goodix (send "sleep", goodix stops requesting regulator on) 2. Other regulator user turns off (regulator fully turns off). 3. Goodix driver gets notified and asserts reset. 4. Other regulator user turns on. 5. Goodix driver gets notified and deasserts reset. 6. Nobody resumes goodix. With that set of steps we'll have reset deasserted but we will have lost the results of the I2C_HID_PWR_SLEEP from the suspend path. That means we might be in higher power than we could be even if the goodix driver thinks things are suspended. Presumably, however, we're still in better shape than if we were asserting "reset" the whole time. If somehow the above situation is actually affecting someone and we want to do better we can deal with it when we have a real use case. Signed-off-by: Douglas Anderson Signed-off-by: Jiri Kosina --- drivers/hid/i2c-hid/i2c-hid-of-goodix.c | 92 ++++++++++++++++++++++++++++----- 1 file changed, 79 insertions(+), 13 deletions(-) (limited to 'drivers/hid') diff --git a/drivers/hid/i2c-hid/i2c-hid-of-goodix.c b/drivers/hid/i2c-hid/i2c-hid-of-goodix.c index ee0225982a82..31a4c229fdb7 100644 --- a/drivers/hid/i2c-hid/i2c-hid-of-goodix.c +++ b/drivers/hid/i2c-hid/i2c-hid-of-goodix.c @@ -26,28 +26,29 @@ struct i2c_hid_of_goodix { struct i2chid_ops ops; struct regulator *vdd; + struct notifier_block nb; + struct mutex regulator_mutex; struct gpio_desc *reset_gpio; const struct goodix_i2c_hid_timing_data *timings; }; -static int goodix_i2c_hid_power_up(struct i2chid_ops *ops) +static void goodix_i2c_hid_deassert_reset(struct i2c_hid_of_goodix *ihid_goodix, + bool regulator_just_turned_on) { - struct i2c_hid_of_goodix *ihid_goodix = - container_of(ops, struct i2c_hid_of_goodix, ops); - int ret; - - ret = regulator_enable(ihid_goodix->vdd); - if (ret) - return ret; - - if (ihid_goodix->timings->post_power_delay_ms) + if (regulator_just_turned_on && ihid_goodix->timings->post_power_delay_ms) msleep(ihid_goodix->timings->post_power_delay_ms); gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 0); if (ihid_goodix->timings->post_gpio_reset_delay_ms) msleep(ihid_goodix->timings->post_gpio_reset_delay_ms); +} - return 0; +static int goodix_i2c_hid_power_up(struct i2chid_ops *ops) +{ + struct i2c_hid_of_goodix *ihid_goodix = + container_of(ops, struct i2c_hid_of_goodix, ops); + + return regulator_enable(ihid_goodix->vdd); } static void goodix_i2c_hid_power_down(struct i2chid_ops *ops) @@ -55,20 +56,54 @@ 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); - gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1); regulator_disable(ihid_goodix->vdd); } +static int ihid_goodix_vdd_notify(struct notifier_block *nb, + unsigned long event, + void *ignored) +{ + struct i2c_hid_of_goodix *ihid_goodix = + container_of(nb, struct i2c_hid_of_goodix, nb); + int ret = NOTIFY_OK; + + mutex_lock(&ihid_goodix->regulator_mutex); + + switch (event) { + case REGULATOR_EVENT_PRE_DISABLE: + gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1); + break; + + case REGULATOR_EVENT_ENABLE: + goodix_i2c_hid_deassert_reset(ihid_goodix, true); + break; + + case REGULATOR_EVENT_ABORT_DISABLE: + goodix_i2c_hid_deassert_reset(ihid_goodix, false); + break; + + default: + ret = NOTIFY_DONE; + break; + } + + mutex_unlock(&ihid_goodix->regulator_mutex); + + return ret; +} + static int i2c_hid_of_goodix_probe(struct i2c_client *client, const struct i2c_device_id *id) { struct i2c_hid_of_goodix *ihid_goodix; - + int ret; ihid_goodix = devm_kzalloc(&client->dev, sizeof(*ihid_goodix), GFP_KERNEL); if (!ihid_goodix) return -ENOMEM; + mutex_init(&ihid_goodix->regulator_mutex); + ihid_goodix->ops.power_up = goodix_i2c_hid_power_up; ihid_goodix->ops.power_down = goodix_i2c_hid_power_down; @@ -84,6 +119,37 @@ static int i2c_hid_of_goodix_probe(struct i2c_client *client, ihid_goodix->timings = device_get_match_data(&client->dev); + /* + * We need to control the "reset" line in lockstep with the regulator + * actually turning on an off instead of just when we make the request. + * This matters if the regulator is shared with another consumer. + * - If the regulator is off then we must assert reset. The reset + * line is active low and on some boards it could cause a current + * leak if left high. + * - If the regulator is on then we don't want reset asserted for very + * long. Holding the controller in reset apparently draws extra + * power. + */ + mutex_lock(&ihid_goodix->regulator_mutex); + ihid_goodix->nb.notifier_call = ihid_goodix_vdd_notify; + ret = regulator_register_notifier(ihid_goodix->vdd, &ihid_goodix->nb); + if (ret) { + mutex_unlock(&ihid_goodix->regulator_mutex); + return dev_err_probe(&client->dev, ret, + "regulator notifier request failed\n"); + } + + /* + * If someone else is holding the regulator on (or the regulator is + * an always-on one) we might never be told to deassert reset. Do it + * now. Here we'll assume that someone else might have _just + * barely_ turned the regulator on so we'll do the full + * "post_power_delay" just in case. + */ + if (ihid_goodix->reset_gpio && regulator_is_enabled(ihid_goodix->vdd)) + goodix_i2c_hid_deassert_reset(ihid_goodix, true); + mutex_unlock(&ihid_goodix->regulator_mutex); + return i2c_hid_core_probe(client, &ihid_goodix->ops, 0x0001); } -- cgit v1.2.3 From 25ddd7cfc582d6001c3b9e18e96c9b3a58523d66 Mon Sep 17 00:00:00 2001 From: Douglas Anderson Date: Tue, 20 Jul 2021 09:07:49 -0700 Subject: HID: i2c-hid: goodix: Use the devm variant of regulator_register_notifier() In commit 18eeef46d359 ("HID: i2c-hid: goodix: Tie the reset line to true state of the regulator") I added a call to regulator_register_notifier() but no call to unregister. That's a bug. Let's use the devm variant to handle the unregistering. Fixes: 18eeef46d359 ("HID: i2c-hid: goodix: Tie the reset line to true state of the regulator") Signed-off-by: Douglas Anderson Signed-off-by: Jiri Kosina --- drivers/hid/i2c-hid/i2c-hid-of-goodix.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/hid') diff --git a/drivers/hid/i2c-hid/i2c-hid-of-goodix.c b/drivers/hid/i2c-hid/i2c-hid-of-goodix.c index 31a4c229fdb7..52674149a275 100644 --- a/drivers/hid/i2c-hid/i2c-hid-of-goodix.c +++ b/drivers/hid/i2c-hid/i2c-hid-of-goodix.c @@ -132,7 +132,7 @@ static int i2c_hid_of_goodix_probe(struct i2c_client *client, */ mutex_lock(&ihid_goodix->regulator_mutex); ihid_goodix->nb.notifier_call = ihid_goodix_vdd_notify; - ret = regulator_register_notifier(ihid_goodix->vdd, &ihid_goodix->nb); + ret = devm_regulator_register_notifier(ihid_goodix->vdd, &ihid_goodix->nb); if (ret) { mutex_unlock(&ihid_goodix->regulator_mutex); return dev_err_probe(&client->dev, ret, -- cgit v1.2.3