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Diffstat (limited to 'Documentation/devicetree/bindings/spi/spi-sprd-adi.txt')
| -rw-r--r-- | Documentation/devicetree/bindings/spi/spi-sprd-adi.txt | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/spi/spi-sprd-adi.txt b/Documentation/devicetree/bindings/spi/spi-sprd-adi.txt new file mode 100644 index 000000000..2567c829e --- /dev/null +++ b/Documentation/devicetree/bindings/spi/spi-sprd-adi.txt @@ -0,0 +1,63 @@ +Spreadtrum ADI controller + +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. + +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. + +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. + +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. + +The new version ADI controller supplies multiple master channels for different +subsystem accessing, that means no need to add hardware spinlock to synchronize, +thus change the hardware spinlock support to be optional to keep backward +compatibility. + +Required properties: +- compatible: Should be "sprd,sc9860-adi". +- reg: Offset and length of ADI-SPI controller register space. +- #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. + +Optional properties: +- 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". +- 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. + +SPI slave nodes must be children of the SPI controller node and can contain +properties described in Documentation/devicetree/bindings/spi/spi-bus.txt. + +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>; + }; |