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dt-bindings: gpio: Add Spreadtrum EIC controller documentation

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This patch adds the device tree bindings for the Spreadtrum EIC
controller. The EIC can be seen as a special type of GPIO, which
can only be used as input mode.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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Baolin Wang 2018-03-05 10:56:50 +08:00 committed by Linus Walleij
parent f79b55d9b9
commit be520cbc85
1 changed files with 97 additions and 0 deletions
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Documentation/devicetree/bindings/gpio/gpio-eic-sprd.txt Normal file
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Spreadtrum EIC controller bindings
The EIC is the abbreviation of external interrupt controller, which can
be used only in input mode. The Spreadtrum platform has 2 EIC controllers,
one is in digital chip, and another one is in PMIC. The digital chip EIC
controller contains 4 sub-modules: EIC-debounce, EIC-latch, EIC-async and
EIC-sync. But the PMIC EIC controller contains only one EIC-debounce sub-
module.
The EIC-debounce sub-module provides up to 8 source input signal
connections. A debounce mechanism is used to capture the input signals'
stable status (millisecond resolution) and a single-trigger mechanism
is introduced into this sub-module to enhance the input event detection
reliability. In addition, this sub-module's clock can be shut off
automatically to reduce power dissipation. Moreover the debounce range
is from 1ms to 4s with a step size of 1ms. The input signal will be
ignored if it is asserted for less than 1 ms.
The EIC-latch sub-module is used to latch some special power down signals
and generate interrupts, since the EIC-latch does not depend on the APB
clock to capture signals.
The EIC-async sub-module uses a 32kHz clock to capture the short signals
(microsecond resolution) to generate interrupts by level or edge trigger.
The EIC-sync is similar with GPIO's input function, which is a synchronized
signal input register. It can generate interrupts by level or edge trigger
when detecting input signals.
Required properties:
- compatible: Should be one of the following:
"sprd,sc9860-eic-debounce",
"sprd,sc9860-eic-latch",
"sprd,sc9860-eic-async",
"sprd,sc9860-eic-sync",
"sprd,sc27xx-eic".
- reg: Define the base and range of the I/O address space containing
the GPIO controller registers.
- gpio-controller: Marks the device node as a GPIO controller.
- #gpio-cells: Should be <2>. The first cell is the gpio number and
the second cell is used to specify optional parameters.
- interrupt-controller: Marks the device node as an interrupt controller.
- #interrupt-cells: Should be <2>. Specifies the number of cells needed
to encode interrupt source.
- interrupts: Should be the port interrupt shared by all the gpios.
Example:
eic_debounce: gpio@40210000 {
compatible = "sprd,sc9860-eic-debounce";
reg = <0 0x40210000 0 0x80>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
interrupts = <GIC_SPI 52 IRQ_TYPE_LEVEL_HIGH>;
};
eic_latch: gpio@40210080 {
compatible = "sprd,sc9860-eic-latch";
reg = <0 0x40210080 0 0x20>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
interrupts = <GIC_SPI 52 IRQ_TYPE_LEVEL_HIGH>;
};
eic_async: gpio@402100a0 {
compatible = "sprd,sc9860-eic-async";
reg = <0 0x402100a0 0 0x20>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
interrupts = <GIC_SPI 52 IRQ_TYPE_LEVEL_HIGH>;
};
eic_sync: gpio@402100c0 {
compatible = "sprd,sc9860-eic-sync";
reg = <0 0x402100c0 0 0x20>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
interrupts = <GIC_SPI 52 IRQ_TYPE_LEVEL_HIGH>;
};
pmic_eic: gpio@300 {
compatible = "sprd,sc27xx-eic";
reg = <0x300>;
interrupt-parent = <&sc2731_pmic>;
interrupts = <5 IRQ_TYPE_LEVEL_HIGH>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
};