[PATCH v2 2/7] HID: i2c-hid-of: skip post-power-on delay if already powered on

[Chen-Yu Tsai <wenst@chromium.org>]

On some devices the HID device is powered from an always-on power rail,
or the power rail has been left on by either POR defaults or the
bootloader. By the time the driver probes, the device most certainly
has finished initializing. There is no need for the delay.

In such designs, the system integrators tend to work around the delay
to avoid the boot time penalty by simply omitting it from the device
tree. This is undesired, as the device tree is not fully describing
the hardware.

Instead, check if the regulator supplies are all enabled, and skip
the post-power-on delay if that is the case.

Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
---
 drivers/hid/i2c-hid/i2c-hid-of.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid-of.c b/drivers/hid/i2c-hid/i2c-hid-of.c
index 59393d71ddb9..70afdfb207ac 100644
--- a/drivers/hid/i2c-hid/i2c-hid-of.c
+++ b/drivers/hid/i2c-hid/i2c-hid-of.c
@@ -29,6 +29,7 @@
 #include <linux/of.h>
 #include <linux/pm.h>
 #include <linux/regulator/consumer.h>
+#include <linux/string_choices.h>
 
 #include "i2c-hid.h"
 
@@ -46,8 +47,12 @@ static int i2c_hid_of_power_up(struct i2chid_ops *ops)
 {
 	struct i2c_hid_of *ihid_of = container_of(ops, struct i2c_hid_of, ops);
 	struct device *dev = &ihid_of->client->dev;
+	bool supply_was_enabled = true;
 	int ret;
 
+	for (unsigned int i = 0; i < ARRAY_SIZE(ihid_of->supplies); i++)
+		supply_was_enabled &= regulator_is_enabled(ihid_of->supplies[i].consumer);
+
 	ret = regulator_bulk_enable(ARRAY_SIZE(ihid_of->supplies),
 				    ihid_of->supplies);
 	if (ret) {
@@ -55,7 +60,8 @@ static int i2c_hid_of_power_up(struct i2chid_ops *ops)
 		return ret;
 	}
 
-	if (ihid_of->post_power_delay_ms)
+	dev_dbg(dev, "supply was %s.\n", str_on_off(supply_was_enabled));
+	if (!supply_was_enabled && ihid_of->post_power_delay_ms)
 		msleep(ihid_of->post_power_delay_ms);
 
 	gpiod_set_value_cansleep(ihid_of->reset_gpio, 0);
-- 
2.55.0.rc0.799.gd6f94ed593-goog