Re: [PATCH] HID: i2c-hid: Send power-on command after reset

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 21-10-2019 09:17, Kai Heng Feng wrote:
> Hi Hans,
> 
>> On Oct 21, 2019, at 5:47 AM, Hans de Goede <hdegoede@redhat.com> wrote:
>>
>> Before commit 67b18dfb8cfc ("HID: i2c-hid: Remove runtime power
>> management"), any i2c-hid touchscreens would typically be runtime-suspended
>> between the driver loading and Xorg or a Wayland compositor opening it,
>> causing it to be resumed again. This means that before this change,
>> we would call i2c_hid_set_power(OFF), i2c_hid_set_power(ON) before the
>> graphical session would start listening to the touchscreen.
>>
>> It turns out that at least some SIS touchscreens, such as the one found
>> on the Asus T100HA, need a power-on command after reset, otherwise they
>> will not send any events.
> 
> As You-Sheng pointed out before, device may need a 60ms delay between ON and RESET command.
> Does adding the delay help?

I just tried increasing the existing usleep between ON and RESET to:

         usleep_range(60000, 70000);

And this does not help. Note that before we had quirks for devices with a SIS
screen needed, where we avoided the reset on resume and instead did just an
i2c_hid_set_power(client, I2C_HID_PWR_ON) for these.

Which likely was to work around the same problem, these devices simply need a
i2c_hid_set_power(client, I2C_HID_PWR_ON) after rest to function.

Assuming other devices do come up in the "ON" state after reset then this
will be a no-op for them and this should thus not impact their operation.

Also I just noticed that 67b18dfb8cfc ("HID: i2c-hid: Remove runtime power management")
has been added to 5.4-rc# as a fix, so we really need to get this in place
to to not avoid regressing devices with a SIS touchscreen actually quite a
few devices including some quite popular ones uses a SIS touchscreen, here
is the list of devices I know about:

Asus T100HA
Asus T200TA
Peaq 10.1" C1010 2-in-1
Toshiba Click Mini L9W-B

Regards,

Hans



>> Fixes: 67b18dfb8cfc ("HID: i2c-hid: Remove runtime power management")
>> Cc: Kai-Heng Feng <kai.heng.feng@canonical.com>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>> drivers/hid/i2c-hid/i2c-hid-core.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
>> index d9c55e30f986..04c088131e04 100644
>> --- a/drivers/hid/i2c-hid/i2c-hid-core.c
>> +++ b/drivers/hid/i2c-hid/i2c-hid-core.c
>> @@ -447,8 +447,12 @@ static int i2c_hid_hwreset(struct i2c_client *client)
>> 	if (ret) {
>> 		dev_err(&client->dev, "failed to reset device.\n");
>> 		i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
>> +		goto out_unlock;
>> 	}
>>
>> +	/* At least some SIS devices need this after reset */
>> +	ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
>> +
>> out_unlock:
>> 	mutex_unlock(&ihid->reset_lock);
>> 	return ret;
>> -- 
>> 2.23.0
>>
>