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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/devicetree/bindings/gpio/spear_spics.txt | |
parent | Initial commit. (diff) | |
download | linux-430c2fc249ea5c0536abd21c23382884005c9093.tar.xz linux-430c2fc249ea5c0536abd21c23382884005c9093.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/devicetree/bindings/gpio/spear_spics.txt')
-rw-r--r-- | Documentation/devicetree/bindings/gpio/spear_spics.txt | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/gpio/spear_spics.txt b/Documentation/devicetree/bindings/gpio/spear_spics.txt new file mode 100644 index 000000000..dd04d96e6 --- /dev/null +++ b/Documentation/devicetree/bindings/gpio/spear_spics.txt @@ -0,0 +1,49 @@ +=== 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 { + num-cs = <3>; + cs-gpios = <&gpio1 7 0>, <&spics 0>, + <&spics 1>; + ... +} |