From b53bc2819a71099ecfc3d61ba0796b3dcc6be321 Mon Sep 17 00:00:00 2001 From: Shiraz Hashim Date: Fri, 16 Nov 2012 10:45:25 +0530 Subject: gpio: SPEAr: add spi chipselect control driver SPEAr platform provides a provision to control chipselects of ARM PL022 Prime Cell spi controller through its system registers, which otherwise remains under PL022 control which some protocols do not want. This commit intends to provide the spi chipselect control in software over gpiolib interface. spi chip drivers can use the exported gpiolib interface to define their chipselect through DT or platform data. Cc: Grant Likely Signed-off-by: Shiraz Hashim Reviewed-by: Vipin Kumar Acked-by: Arnd Bergmann Signed-off-by: Viresh Kumar Signed-off-by: Linus Walleij --- .../devicetree/bindings/gpio/spear_spics.txt | 50 ++++++++++++++++++++++ 1 file changed, 50 insertions(+) create mode 100644 Documentation/devicetree/bindings/gpio/spear_spics.txt (limited to 'Documentation') diff --git a/Documentation/devicetree/bindings/gpio/spear_spics.txt b/Documentation/devicetree/bindings/gpio/spear_spics.txt new file mode 100644 index 000000000000..96c37eb15075 --- /dev/null +++ b/Documentation/devicetree/bindings/gpio/spear_spics.txt @@ -0,0 +1,50 @@ +=== ST Microelectronics SPEAr SPI CS Driver === + +SPEAr platform provides a provision to control chipselects of ARM PL022 Prime +Cell spi controller through its system registers, which otherwise remains under +PL022 control. If chipselect remain under PL022 control then they would be +released as soon as transfer is over and TxFIFO becomes empty. This is not +desired by some of the device protocols above spi which expect (multiple) +transfers without releasing their chipselects. + +Chipselects can be controlled by software by turning them as GPIOs. SPEAr +provides another interface through system registers through which software can +directly control each PL022 chipselect. Hence, it is natural for SPEAr to export +the control of this interface as gpio. + +Required properties: + + * compatible: should be defined as "st,spear-spics-gpio" + * reg: mentioning address range of spics controller + * st-spics,peripcfg-reg: peripheral configuration register offset + * st-spics,sw-enable-bit: bit offset to enable sw control + * st-spics,cs-value-bit: bit offset to drive chipselect low or high + * st-spics,cs-enable-mask: chip select number bit mask + * st-spics,cs-enable-shift: chip select number program offset + * gpio-controller: Marks the device node as gpio controller + * #gpio-cells: should be 1 and will mention chip select number + +All the above bit offsets are within peripcfg register. + +Example: +------- +spics: spics@e0700000{ + compatible = "st,spear-spics-gpio"; + reg = <0xe0700000 0x1000>; + st-spics,peripcfg-reg = <0x3b0>; + st-spics,sw-enable-bit = <12>; + st-spics,cs-value-bit = <11>; + st-spics,cs-enable-mask = <3>; + st-spics,cs-enable-shift = <8>; + gpio-controller; + #gpio-cells = <2>; +}; + + +spi0: spi@e0100000 { + status = "okay"; + num-cs = <3>; + cs-gpios = <&gpio1 7 0>, <&spics 0>, + <&spics 1>; + ... +} -- cgit v1.3-18-gd494