Rockchip RK3399 PWM driver

[manu]

Summary

Here's a stab at a PWM driver for the rockchip rk3399, using the new PWM api. I have never written a driver before, but it seemed pretty straightforward.

The hardware itself is four channel, but the dts assumes multiple attachment for some reason.

I can control the fan on my ROCKPRO64 by enabling the second pwm in the device tree:

Index: sys/gnu/dts/arm64/rockchip/rk3399-rockpro64.dts
===================================================================
--- sys/gnu/dts/arm64/rockchip/rk3399-rockpro64.dts	(revision 343327)
+++ sys/gnu/dts/arm64/rockchip/rk3399-rockpro64.dts	(working copy)
@@ -560,6 +560,10 @@
 	status = "okay";
 };
 
+&pwm1 {
+	status = "okay";
+};
+
 &pwm2 {
 	status = "okay";
 };

Test Plan

Tested on the PinebookPro with the backlight.

[andrew]

sys/arm64/rockchip/rk_pwm.c

158

Do we need sc->dev? Everywhere it's used we have access the it as an argument.

237

This should be:

/*
 * The device ...

274–275

Multi line comments should be in the format

/*
 * First line.
 * Second line.
 */

[manu]

sys/arm64/rockchip/rk_pwm.c

166

you should check for error here.

230

clock should be released here.

243

This comment isn't needed, we are respecting the bindings.

280

Why ?

295

This should only happen in pwm_enable.

298

You always set using_scaler to false, just clear the clock source bit and remove the variable.

300

same here, prescaler is always 0.

302

same here, scaler is always 0.

[bdragon]

sys/arm64/rockchip/rk_pwm.c

280

So the period can be longer than a couple seconds or so. If this isn't desired in a PWM driver, I can just simplify stuff and leave scaling and prescaling off at all times instead of implementing it, since the API will overflow before the hardware will. I was assuming people would be using this for stuff like watering timers etc where the period would be in minutes or hours, but personally I just wanted the fan to spin on my rockpro64.

[manu]

sys/arm64/rockchip/rk_pwm.c

280

I really don't need that we need period > 1s honestly.

[bdragon]

Will address comments and catch up with the latest API changes soon. Poking at it this evening.

[manu]

Update the latest pwm api.

[manu]

Handle clock errors.