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When the power supply is shared with other peripherals the reset line
can be wired in such a way that it can remain deasserted regardless of
whether the supply is on or not.
This is important as it can be used to avoid holding the controller in
reset for extended periods of time when it remains powered, something
which can lead to increased power consumption. Leaving reset deasserted
also avoids leaking current through the reset circuitry pull-up
resistors.
Add a new 'no-reset-on-power-off' devicetree property which can be used
by the OS to determine when reset needs to be asserted on power down.
Note that this property can also be used when the supply cannot be
turned off by the OS at all.
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240507144821.12275-4-johan+linaro@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
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Add a compatible string for the Elan eKTH5015M touch controller.
Judging from the current binding and commit bd3cba00dcc6 ("HID: i2c-hid:
elan: Add support for Elan eKTH6915 i2c-hid touchscreens"), eKTH5015M
appears to be compatible with eKTH6915. Notably the power-on sequence is
the same.
While at it, drop a redundant label from the example.
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20240507144821.12275-3-johan+linaro@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
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The Ilitek ILI2901 touch screen controller was apparently incorrectly
added to the Elan eKTH6915 schema simply because it also has a reset
gpio and is currently managed by the Elan driver in Linux.
The two controllers are not related even if an unfortunate wording in
the commit message adding the Ilitek compatible made it sound like they
were.
Add a dedicated schema for the ILI2901 which does not specify the I2C
address (which is likely 0x41 rather than 0x10 as for other Ilitek touch
controllers) to avoid cluttering the Elan schema with unrelated devices
and to make it easier to find the correct schema when adding further
Ilitek controllers.
Fixes: d74ac6f60a7e ("dt-bindings: HID: i2c-hid: elan: Introduce Ilitek ili2901")
Cc: Zhengqiao Xia <xiazhengqiao@huaqin.corp-partner.google.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20240507144821.12275-2-johan+linaro@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
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The Ilitek ili2901 touch screen chip same as Elan eKTH6915 controller
has a reset gpio. The difference is that they have different
post_power_delay_ms and post_gpio_reset_on_delay_ms.
Ilitek ili2901 also uses 3.3V power supply.
Signed-off-by: Zhengqiao Xia <xiazhengqiao@huaqin.corp-partner.google.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
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As talked about in the patch ("drm/panel: Add a way for other devices
to follow panel state"), touchscreens that are connected to panels are
generally expected to be power sequenced together with the panel
they're attached to. Today, nothing provides information allowing you
to find out that a touchscreen is connected to a panel. Let's add a
phandle for this.
The proerty is added to the generic touchscreen bindings and then
enabled in the bindings for the i2c-hid backed devices. This can and
should be added for other touchscreens in the future, but for now
let's start small.
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Benjamin Tissoires <bentiss@kernel.org>
Acked-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230727101636.v4.1.Id68e30343bb1e11470582a9078b086176cfec46b@changeid
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Like many i2c-hid touchscreen controllers, the Elan eKTH6915
controller has a reset gpio. For the Goodix GT7375P touchscreen the
decision was to add a new binding rather than trying to add a new GPIO
to the existing i2c-hid binding. We'll follow the lead and do it here,
too.
SIDE NOTE: the Elan eKTH6915 is a touchscreen _controller_ that's
included as a part on some touchscreens. The reset line isn't truly
necessary for the functioning of the touchscreen, so it's possible
that some designs won't have it hooked up and will just guarantee the
power sequencing requirements with RLC circuits. Thus, we'll mark the
reset gpio as optional.
Note that if the reset GPIO isn't used there's actually no true need
to use the "elan,ekth6915" compatible instead of the "hid-over-i2c" on
Linux. However:
- Officially using just "hid-over-i2c" for this device violates the
existing "hid-over-i2c" bindings. The bindings say that you're not
supposed to use "post-power-on-delay-ms" without specifying a more
specific compatible. Currently the Linux driver doesn't enforce
this, but it violates the bindings to just use
"hid-over-i2c". ...and if you're going to add a more specific
compatible anyway, might as well do it right.
- Using this compatible means we don't need to specify
"hid-descr-addr" since it's inferred from the compatible.
- Using this compatible means that the regulator names match the names
on the Elan datasheet (vcc33 / vccio) vs the generic hid-over-i2c
(vdd / vddl).
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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