From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Kosina Subject: Re: [PATCH] HID: i2c-hid: Add a small delay after powering on/off the device Date: Wed, 3 Oct 2018 11:10:02 +0200 (CEST) Message-ID: References: <20181001035313.21453-1-kai.heng.feng@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: <20181001035313.21453-1-kai.heng.feng@canonical.com> Sender: linux-kernel-owner@vger.kernel.org To: Kai-Heng Feng Cc: benjamin.tissoires@redhat.com, hdegoede@redhat.com, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-input@vger.kernel.org On Mon, 1 Oct 2018, Kai-Heng Feng wrote: > Raydium touchpanel (2386:4B33) sometimes does not workin desktop session > although it works in display manager. > > During user logging, the display manager exits, close the HID device, > then the device gets runtime suspended and powered off. The desktop > session begins shortly after, opens the HID device, then the device gets > runtime resumed and powered on. > > If the trasition from display manager to desktop sesesion is fast, the > touchpanel cannot switch from powered off to powered on in short > timeframe. So add a small delay to workaround the issue. > > Signed-off-by: Kai-Heng Feng > --- > drivers/hid/i2c-hid/i2c-hid.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c > index f3076659361a..ff5682cc1bce 100644 > --- a/drivers/hid/i2c-hid/i2c-hid.c > +++ b/drivers/hid/i2c-hid/i2c-hid.c > @@ -409,6 +409,8 @@ static int i2c_hid_set_power(struct i2c_client *client, int power_state) > > if (ret) > dev_err(&client->dev, "failed to change power setting.\n"); > + else > + msleep(20); In case there really is no other way around it, at least please add comment explaining why this ugly msleep() is there. Thanks, -- Jiri Kosina SUSE Labs