pwm: atmel: add Timer Counter Block PWM driver

This patch adds a PWM driver based on Atmel Timer Counter Block. The
Timer Counter Block is used in Waveform generator mode.

A Timer Counter Block provides up to 6 PWM devices grouped by 2:
* group 0 = PWM 0 and 1
* group 1 = PWM 2 and 3
* group 2 = PMW 4 and 5

PWM devices in a given group must be configured with the same period
value. If a PWM device in a group tries to change the period value and
the other device is already configured with a different value an error
will be returned.

This driver requires device tree support. The Timer Counter Block number
used to create a PWM chip is given by the tc-block field in an
"atmel,tcb-pwm" compatible node.

This patch was tested on kizbox board (at91sam9g20 SoC) with pwm-leds.

Signed-off-by: Boris BREZILLON <linux-arm@overkiz.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

1 files changed, 18 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt b/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt
new file mode 100644
index 000000000000..de0eaed86651
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/atmel-tcb-pwm.txt
@@ -0,0 +1,18 @@
+Atmel TCB PWM controller
+
+Required properties:
+- compatible: should be "atmel,tcb-pwm"
+- #pwm-cells: Should be 3.  The first cell specifies the per-chip index
+  of the PWM to use, the second cell is the period in nanoseconds and
+  bit 0 in the third cell is used to encode the polarity of PWM output.
+  Set bit 0 of the third cell in PWM specifier to 1 for inverse polarity &
+  set to 0 for normal polarity.
+- tc-block: The Timer Counter block to use as a PWM chip.
+
+Example:
+
+pwm {
+	compatible = "atmel,tcb-pwm";
+	#pwm-cells = <3>;
+	tc-block = <1>;
+};