summaryrefslogtreecommitdiff
path: root/doc
diff options
context:
space:
mode:
authorKlaus H. Sorensen <khso@prevas.dk>2020-02-11 15:20:22 +0000
committerTom Rini <trini@konsulko.com>2020-03-31 10:06:52 -0400
commit3fb22bc2f825ea1b3326edc5b32d711a759a265f (patch)
treeefa15fbaac2202fc0ef0bc10aad9161cb4468689 /doc
parentdd4cf53f9864362d9e92472298ad60dcbb8b7e72 (diff)
gpio/mpc83xx_spisel_boot.c: gpio driver for SPISEL_BOOT signal
Some SoCs in the mpc83xx family, e.g. mpc8309, have a dedicated spi chip select, SPISEL_BOOT, that is used by the boot code to boot from flash. This chip select will typically be used to select a SPI boot flash. The SPISEL_BOOT signal is controlled by a single bit in the SPI_CS register. Implement a gpio driver for the spi chip select register. This allows a spi driver capable of using gpios as chip select, to bind a chip select to SPISEL_BOOT. It may be a little odd to do this as a GPIO driver, since the signal is neither GP or I, but it is quite convenient to present it to the spi driver that way. The alternative it to teach mpc8xxx_spi to handle the SPISEL_BOOT signal itself (that is how it's done in the linux kernel, see commit 69b921acae8a) Signed-off-by: Klaus H. Sorensen <khso@prevas.dk> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Diffstat (limited to 'doc')
-rw-r--r--doc/device-tree-bindings/gpio/fsl,mpc83xx-spisel-boot.txt22
1 files changed, 22 insertions, 0 deletions
diff --git a/doc/device-tree-bindings/gpio/fsl,mpc83xx-spisel-boot.txt b/doc/device-tree-bindings/gpio/fsl,mpc83xx-spisel-boot.txt
new file mode 100644
index 0000000000..52d8bb0a5c
--- /dev/null
+++ b/doc/device-tree-bindings/gpio/fsl,mpc83xx-spisel-boot.txt
@@ -0,0 +1,22 @@
+MPC83xx SPISEL_BOOT gpio controller
+
+Provide access to MPC83xx SPISEL_BOOT signal as a gpio to allow it to be
+easily bound as a SPI controller chip select.
+
+The SPISEL_BOOT signal is always an output.
+
+Required properties:
+
+- compatible: must be "fsl,mpc83xx-spisel-boot" or "fsl,mpc8309-spisel-boot".
+- reg: must point to the SPI_CS register in the SoC register map.
+- ngpios: number of gpios provided by driver, normally 1.
+
+Example:
+
+ spisel_boot: spisel_boot@14c {
+ compatible = "fsl,mpc8309-spisel-boot";
+ reg = <0x14c 0x04>;
+ #gpio-cells = <2>;
+ device_type = "gpio";
+ ngpios = <1>;
+ };