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

[Kai-Heng Feng <kai.heng.feng@canonical.com>]

Hi Hans,

> On Oct 31, 2019, at 01:39, Kai-Heng Feng <kai.heng.feng@canonical.com> wrote:
> 
> Hi Hans,
> 
>> On Oct 30, 2019, at 23:11, Hans de Goede <hdegoede@redhat.com> wrote:
>> 
>> 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:
> 
> I agree we should use this workaround since increasing delay doesn't work.

I just checked the spec again, seems like ON before RESET in probe is unnecessary.
Does removing the ON command in probe help?

> 
> Kai-Heng
> 
>> 
>> 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