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Spreadtrum ADI controller | ||
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ADI is the abbreviation of Anolog-Digital interface, which is used to access | ||
analog chip (such as PMIC) from digital chip. ADI controller follows the SPI | ||
framework for its hardware implementation is alike to SPI bus and its timing | ||
is compatile to SPI timing. | ||
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ADI controller has 50 channels including 2 software read/write channels and | ||
48 hardware channels to access analog chip. For 2 software read/write channels, | ||
users should set ADI registers to access analog chip. For hardware channels, | ||
we can configure them to allow other hardware components to use it independently, | ||
which means we can just link one analog chip address to one hardware channel, | ||
then users can access the mapped analog chip address by this hardware channel | ||
triggered by hardware components instead of ADI software channels. | ||
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Thus we introduce one property named "sprd,hw-channels" to configure hardware | ||
channels, the first value specifies the hardware channel id which is used to | ||
transfer data triggered by hardware automatically, and the second value specifies | ||
the analog chip address where user want to access by hardware components. | ||
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Since we have multi-subsystems will use unique ADI to access analog chip, when | ||
one system is reading/writing data by ADI software channels, that should be under | ||
one hardware spinlock protection to prevent other systems from reading/writing | ||
data by ADI software channels at the same time, or two parallel routine of setting | ||
ADI registers will make ADI controller registers chaos to lead incorrect results. | ||
Then we need one hardware spinlock to synchronize between the multiple subsystems. | ||
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Required properties: | ||
- compatible: Should be "sprd,sc9860-adi". | ||
- reg: Offset and length of ADI-SPI controller register space. | ||
- hwlocks: Reference to a phandle of a hwlock provider node. | ||
- hwlock-names: Reference to hwlock name strings defined in the same order | ||
as the hwlocks, should be "adi". | ||
- #address-cells: Number of cells required to define a chip select address | ||
on the ADI-SPI bus. Should be set to 1. | ||
- #size-cells: Size of cells required to define a chip select address size | ||
on the ADI-SPI bus. Should be set to 0. | ||
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Optional properties: | ||
- sprd,hw-channels: This is an array of channel values up to 49 channels. | ||
The first value specifies the hardware channel id which is used to | ||
transfer data triggered by hardware automatically, and the second | ||
value specifies the analog chip address where user want to access | ||
by hardware components. | ||
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SPI slave nodes must be children of the SPI controller node and can contain | ||
properties described in Documentation/devicetree/bindings/spi/spi-bus.txt. | ||
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Example: | ||
adi_bus: spi@40030000 { | ||
compatible = "sprd,sc9860-adi"; | ||
reg = <0 0x40030000 0 0x10000>; | ||
hwlocks = <&hwlock1 0>; | ||
hwlock-names = "adi"; | ||
#address-cells = <1>; | ||
#size-cells = <0>; | ||
sprd,hw-channels = <30 0x8c20>; | ||
}; |
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