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From: Linus Walleij <linus.walleij@linaro.org>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Nick Dyer <nick@shmanahar.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Jiada Wang <jiada_wang@mentor.com>,
	Linux Input <linux-input@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	linux-tegra <linux-tegra@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/3] Input: atmel_mxt_ts - support wakeup methods
Date: Sun, 6 Dec 2020 16:20:28 +0100	[thread overview]
Message-ID: <CACRpkdZoxsamwCpckeMOVSkK_DQOqakmZ3fHzYb8CeSGZ1V_NA@mail.gmail.com> (raw)
In-Reply-To: <20201205054749.26487-3-digetx@gmail.com>

On Sat, Dec 5, 2020 at 6:48 AM Dmitry Osipenko <digetx@gmail.com> wrote:

> According to datasheets, chips like mXT1386 have a WAKE line, it is used
> to wake the chip up from deep sleep mode before communicating with it via
> the I2C-compatible interface.
>
> If the WAKE line is connected to a GPIO line, the line must be asserted
> 25 ms before the host attempts to communicate with the controller. If the
> WAKE line is connected to the SCL pin, the controller will send a NACK on
> the first attempt to address it, the host must then retry 25 ms later.
>
> Implement the wake-up methods in the driver. Touchscreen now works
> properly on devices like Acer A500 tablet, fixing problems like this:
>
>  atmel_mxt_ts 0-004c: __mxt_read_reg: i2c transfer failed (-121)
>  atmel_mxt_ts 0-004c: mxt_bootloader_read: i2c recv failed (-121)
>  atmel_mxt_ts 0-004c: Trying alternate bootloader address
>  atmel_mxt_ts 0-004c: mxt_bootloader_read: i2c recv failed (-121)
>  atmel_mxt_ts: probe of 0-004c failed with error -121
>
> Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>

OK looks interesting!

> +       /* Request the WAKE line as asserted so controller won't sleep */
> +       data->wake_gpio = devm_gpiod_get_optional(&client->dev,
> +                                                 "wake", GPIOD_OUT_HIGH);
> +       if (IS_ERR(data->wake_gpio)) {
> +               error = PTR_ERR(data->wake_gpio);
> +               dev_err(&client->dev, "Failed to get wake gpio: %d\n", error);
> +               return error;
> +       }

That is a bit brutal, don't you think? Now you force the controller
to be on at all times. Even across suspend/resume.

Shouldn't the same patch drive this low in mxt_suspend()
and driver it high + wait 25 ms in mxt_resume()?
Waiting 25ms in mxt_resume() is chill, it is anyway on the
slowpath.

Yours,
Linus Walleij

  reply	other threads:[~2020-12-06 15:22 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-05  5:47 [PATCH v2 0/3] Support wakeup methods of Atmel maXTouch controllers Dmitry Osipenko
2020-12-05  5:47 ` [PATCH v2 1/3] dt-bindings: input: atmel_mxt_ts: Document atmel,wakeup-method and wake-GPIO Dmitry Osipenko
2020-12-05  5:47 ` [PATCH v2 2/3] Input: atmel_mxt_ts - support wakeup methods Dmitry Osipenko
2020-12-06 15:20   ` Linus Walleij [this message]
2020-12-06 19:42     ` Dmitry Osipenko
2020-12-05  5:47 ` [PATCH v2 3/3] ARM: tegra: acer-a500: Add atmel,wakeup-method property Dmitry Osipenko

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