From: Johan Hovold <johan@kernel.org>
To: "Łukasz Majczak" <lma@chromium.org>
Cc: Jiri Kosina <jikos@kernel.org>,
Dmitry Torokhov <dtor@chromium.org>,
Benjamin Tissoires <benjamin.tissoires@redhat.com>,
Douglas Anderson <dianders@chromium.org>,
Hans de Goede <hdegoede@redhat.com>,
Maxime Ripard <mripard@kernel.org>,
Kai-Heng Feng <kai.heng.feng@canonical.com>,
Johan Hovold <johan+linaro@kernel.org>,
linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
Radoslaw Biernacki <rad@chromium.org>
Subject: Re: [PATCH v2] HID: i2c-hid: wait for i2c touchpad deep-sleep to power-up transition
Date: Tue, 9 Apr 2024 17:46:15 +0200 [thread overview]
Message-ID: <ZhVix-HJrqQbiPrB@hovoldconsulting.com> (raw)
In-Reply-To: <CAE5UKNqufWZfKLAXLcpBYKQpJEVt6jPD4Xtr=Nesh34VkNOETg@mail.gmail.com>
On Tue, Apr 09, 2024 at 12:53:43PM +0200, Łukasz Majczak wrote:
> > Can you please explain why this would not a problem for all future
> > transactions as well?
> The problem is that the probe function calling i2c_smbus_read_byte()
> is not aware that
> uC on the other end is in a deep sleep state so the first read will
> fail and so the whole probe.
>
> In a normal scenario, when a user touches the touchpad (when it is in
> a deep sleep), the touch will first wake up the uC and
> then generate an interrupt to AP, so in this case the touchpad is
> fully awake and operational.
Sure, but what about other transactions that are initiated by the host
(e.g. SET_POWER)?
Perhaps this hack at probe is enough for your use case, but is an
incomplete hack and at a minimum you'd need to add a comment explaining
why it is there.
Johan
next prev parent reply other threads:[~2024-04-09 15:46 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-05 10:24 [PATCH v2] HID: i2c-hid: wait for i2c touchpad deep-sleep to power-up transition Lukasz Majczak
2024-04-08 3:18 ` Doug Anderson
2024-04-08 7:27 ` Johan Hovold
2024-04-09 10:53 ` Łukasz Majczak
2024-04-09 15:46 ` Johan Hovold [this message]
2024-04-11 14:23 ` Łukasz Majczak
2024-04-12 6:28 ` Kai-Heng Feng
2024-04-15 9:08 ` Johan Hovold
2024-04-15 12:26 ` Radoslaw Biernacki
2024-04-15 13:37 ` Johan Hovold
2024-04-15 10:28 ` Kenny Levinsen
2024-04-15 12:10 ` Radoslaw Biernacki
2024-04-15 12:13 ` Radoslaw Biernacki
2024-04-15 13:22 ` Johan Hovold
2024-04-15 17:14 ` Kenny Levinsen
2024-04-23 11:32 ` Łukasz Majczak
2024-04-23 13:01 ` Kenny Levinsen
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