linux-kernel - Re: [PATCH v2] HID: i2c-hid: wait for i2c touchpad deep-sleep to power-up transition

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Date: Sun, 7 Apr 2024 20:18:10 -0700
From: Doug Anderson <dianders@...omium.org>
To: Lukasz Majczak <lma@...omium.org>
Cc: Jiri Kosina <jikos@...nel.org>, Dmitry Torokhov <dtor@...omium.org>, 
	Benjamin Tissoires <benjamin.tissoires@...hat.com>, Hans de Goede <hdegoede@...hat.com>, 
	Maxime Ripard <mripard@...nel.org>, Kai-Heng Feng <kai.heng.feng@...onical.com>, 
	Johan Hovold <johan+linaro@...nel.org>, linux-input@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Radoslaw Biernacki <rad@...omium.org>
Subject: Re: [PATCH v2] HID: i2c-hid: wait for i2c touchpad deep-sleep to
 power-up transition

Hi,

On Fri, Apr 5, 2024 at 3:24 AM Lukasz Majczak <lma@...omium.org> wrote:
>
> 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 being
> detected due initial transaction being dropped by STM i2c slave controller.
> 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@...omium.org>
> Signed-off-by: Radoslaw Biernacki <rad@...omium.org>
> Signed-off-by: Lukasz Majczak <lma@...omium.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@...omium.org>

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