pwm: vt8500: Add polarity support

Add support to set polarity on PWM devices, allowing for inverted
duty cycles.

Also update the binding document to #pwm-cells = <3> to allow
passing the flags from devicetree.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

2 files changed, 29 insertions, 3 deletions

diff --git a/Documentation/devicetree/bindings/pwm/vt8500-pwm.txt b/Documentation/devicetree/bindings/pwm/vt8500-pwm.txt
index bcc63678a9a5..d21d82d29855 100644
--- a/Documentation/devicetree/bindings/pwm/vt8500-pwm.txt
+++ b/Documentation/devicetree/bindings/pwm/vt8500-pwm.txt
@@ -3,14 +3,17 @@ VIA/Wondermedia VT8500/WM8xxx series SoC PWM controller
 Required properties:
 - compatible: should be "via,vt8500-pwm"
 - reg: physical base address and length of the controller's registers
-- #pwm-cells: should be 2.  The first cell specifies the per-chip index
-  of the PWM to use and the second cell is the period in nanoseconds.
+- #pwm-cells: Should be 3. Number of cells being used to specify PWM property.
+  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 in PWM specifier
+  to 1 for inverse polarity & set to 0 for normal polarity.
 - clocks: phandle to the PWM source clock
 
 Example:
 
 pwm1: pwm@d8220000 {
-        #pwm-cells = <2>;
+        #pwm-cells = <3>;
         compatible = "via,vt8500-pwm";
         reg = <0xd8220000 0x1000>;
         clocks = <&clkpwm>;
diff --git a/drivers/pwm/pwm-vt8500.c b/drivers/pwm/pwm-vt8500.c
index bbc37504103a..98d79e9f0144 100644
--- a/drivers/pwm/pwm-vt8500.c
+++ b/drivers/pwm/pwm-vt8500.c
@@ -164,10 +164,31 @@ static void vt8500_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
         clk_disable(vt8500->clk);
 }
 
+static int vt8500_pwm_set_polarity(struct pwm_chip *chip,
+                                   struct pwm_device *pwm,
+                                   enum pwm_polarity polarity)
+{
+        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
+        u32 val;
+
+        val = readl(vt8500->base + REG_CTRL(pwm->hwpwm));
+
+        if (polarity == PWM_POLARITY_INVERSED)
+                val |= CTRL_INVERT;
+        else
+                val &= ~CTRL_INVERT;
+
+        writel(val, vt8500->base + REG_CTRL(pwm->hwpwm));
+        pwm_busy_wait(vt8500, pwm->hwpwm, STATUS_CTRL_UPDATE);
+
+        return 0;
+}
+
 static struct pwm_ops vt8500_pwm_ops = {
         .enable = vt8500_pwm_enable,
         .disable = vt8500_pwm_disable,
         .config = vt8500_pwm_config,
+        .set_polarity = vt8500_pwm_set_polarity,
         .owner = THIS_MODULE,
 };
 
@@ -197,6 +218,8 @@ static int vt8500_pwm_probe(struct platform_device *pdev)
 
         chip->chip.dev = &pdev->dev;
         chip->chip.ops = &vt8500_pwm_ops;
+        chip->chip.of_xlate = of_pwm_xlate_with_flags;
+        chip->chip.of_pwm_n_cells = 3;
         chip->chip.base = -1;
         chip->chip.npwm = VT8500_NR_PWMS;