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From: Doug Anderson <dianders@chromium.org>
Date: Sun, 7 Apr 2024 20:18:10 -0700
Message-ID: <CAD=FV=U4kLZMSViOMcUaXEJd8E2avb7wiBx=Y=Uad+04Q5LHXw@mail.gmail.com>
Subject: Re: [PATCH v2] HID: i2c-hid: wait for i2c touchpad deep-sleep to
 power-up transition
To: Lukasz Majczak <lma@chromium.org>
Cc: Jiri Kosina <jikos@kernel.org>, Dmitry Torokhov <dtor@chromium.org>, 
	Benjamin Tissoires <benjamin.tissoires@redhat.com>, 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>
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Hi,

On Fri, Apr 5, 2024 at 3:24=E2=80=AFAM Lukasz Majczak <lma@chromium.org> wr=
ote:
>
> This patch extends the early bailout for probing procedure introduced in
> commit b3a81b6c4fc6 ("HID: i2c-hid: check if device is there before
> really probing"), in order to cover devices
> based on STM microcontrollers. For touchpads based on STM uC,
> the probe sequence needs to take into account the increased response time
> for i2c transaction if the device already entered a deep power state.
> STM specify the wakeup time as 400us between positive strobe of
> the clock line. Deep sleep is controlled by Touchpad FW,
> though some devices enter it pretty early to conserve power
> in case of lack of activity on the i2c bus.
> Failing to follow this requirement will result in touchpad device not bei=
ng
> detected due initial transaction being dropped by STM i2c slave controlle=
r.
> By adding additional try, first transaction will wake up the touchpad
> STM controller, and the second will produce proper detection response.
>
> v1->v2:
> * Updated commit message with short sha of a base commit and proper tags
> * Rearranged while loop to perform check only once
> * Loosened sleeping range
>
> Co-developed-by: Radoslaw Biernacki <rad@chromium.org>
> Signed-off-by: Radoslaw Biernacki <rad@chromium.org>
> Signed-off-by: Lukasz Majczak <lma@chromium.org>
> ---
>  drivers/hid/i2c-hid/i2c-hid-core.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)

As per my review comments in response to your v1 [1], this seems
reasonable to me.

Reviewed-by: Douglas Anderson <dianders@chromium.org>

[1] https://lore.kernel.org/r/20240325105452.529921-1-lma@chromium.org