reset: Add driver for gpio-controlled reset pins

This driver implements a reset controller device that toggle a gpio
connected to a reset pin of a peripheral IC. The delay between assertion
and de-assertion of the reset signal can be configured via device tree.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
[shawn.guo: cherry-pick commit 27e3604c82cb from imx_3.10.y]
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>

Conflicts:
	drivers/reset/Makefile

(cherry picked from commit 2c8ba990ad6b33bd28f72384fbd238e0aca6c886)

Conflicts:
	drivers/reset/Kconfig
	drivers/reset/Makefile

1 files changed, 35 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/reset/gpio-reset.txt b/Documentation/devicetree/bindings/reset/gpio-reset.txt
new file mode 100644
index 000000000000..bca5348a5131
--- /dev/null
+++ b/Documentation/devicetree/bindings/reset/gpio-reset.txt
@@ -0,0 +1,35 @@
+GPIO reset controller
+=====================
+
+A GPIO reset controller controls a single GPIO that is connected to the reset
+pin of a peripheral IC. Please also refer to reset.txt in this directory for
+common reset controller binding usage.
+
+Required properties:
+- compatible: Should be "gpio-reset"
+- reset-gpios: A gpio used as reset line. The gpio specifier for this property
+               depends on the gpio controller that provides the gpio.
+- #reset-cells: 0, see below
+
+Optional properties:
+- reset-delay-us: delay in microseconds. The gpio reset line will be asserted for
+                  this duration to reset.
+- initially-in-reset: boolean. If not set, the initial state should be a
+                      deasserted reset line. If this property exists, the
+                      reset line should be kept in reset.
+
+example:
+
+sii902x_reset: gpio-reset {
+	compatible = "gpio-reset";
+	reset-gpios = <&gpio5 0 GPIO_ACTIVE_LOW>;
+	reset-delay-us = <10000>;
+	initially-in-reset;
+	#reset-cells = <0>;
+};
+
+/* Device with nRESET pin connected to GPIO5_0 */
+sii902x@39 {
+	/* ... */
+	resets = <&sii902x_reset>; /* active-low GPIO5_0, 10 ms delay */
+};