[PATCH v2 2/4] dt-bindings: ARM: Mediatek: Document devicetree bindings for spi bus
From: Daniel Kurtz <hidden>
Date: 2015-07-02 03:05:23
Also in:
linux-devicetree, linux-mediatek, linux-spi, lkml
On Mon, Jun 29, 2015 at 9:04 PM, Leilk Liu [off-list ref] wrote:
quoted hunk ↗ jump to hunk
Signed-off-by: Leilk Liu <redacted> --- .../devicetree/bindings/spi/spi-mt65xx.txt | 32 ++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 Documentation/devicetree/bindings/spi/spi-mt65xx.txtdiff --git a/Documentation/devicetree/bindings/spi/spi-mt65xx.txt b/Documentation/devicetree/bindings/spi/spi-mt65xx.txt new file mode 100644 index 0000000..04c28fd --- /dev/null +++ b/Documentation/devicetree/bindings/spi/spi-mt65xx.txt@@ -0,0 +1,32 @@ +MTK SPI device + +Required properties: +- compatible: should be one of the following. + - mediatek,mt8173-spi: for mt8173 platforms + - mediatek,mt8135-spi: for mt8135 platforms + - mediatek,mt6589-spi: for mt6589 platforms + +- reg: Address and length of the register set for the device + +- interrupts: Should contain spi interrupt + +- clock-names: tuple listing input clock names. + Required elements: "main" + +- clocks: phandles to input clocks. + +- pad-select: should specify spi pad used, only required for MT8173. + This value should be 0~3. + +Example: + +- SoC Specific Portion: +spi: spi at 1100a000 { + compatible = "mediatek,mt8173-spi"; + reg = <0 0x1100a000 0 0x1000>; + interrupts = <GIC_SPI 110 IRQ_TYPE_LEVEL_LOW>; + clocks = <&pericfg PERI_SPI0>;
CLK_PERI_SPI0
+ clock-names = "main"; + pad-select = <1>;
According to [0], a SPI bus should also specify address-cells/size-cells to allow SPI bus devices to specify a chip select. [0] Documentation/devicetree/bindings/spi/spi-bus.txt - #address-cells - number of cells required to define a chip select address on the SPI bus. - #size-cells - should be zero. The spi-bus document even describes how to mix "native" and gpio CS lines. I am still not sure what to do with the "pad-select" feature. Does "pad-select" just select one of 4 dedicated chip select lines? Or, does it also change which CK/MOSI/MISO lines are used? Ideally, the same CK/MOSI/MISO signals are sent on all CK/MOSI/MISO lines enabled by pinctrl, and "pad-select" just chooses which CS_N line to use. In this case, we can use the SPI slave device reg value to select which CS_N to use for any given device. Furthermore, we can also support using additional cs-gpios. However, if the pad-select also specifies which CK/MOSI/MISO pins are used for a given transaction, then supporting cs-gpios becomes a bit trickier, since the spi slave device would need to specify both which gpio-cs to use, as well as which SPI pad it is connected to. -Dan
+ status = "disabled"; +}; -- 1.8.1.1.dirty _______________________________________________ Linux-mediatek mailing list Linux-mediatek at lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek