pwm: omap-dmtimer: Allow for setting dmtimer clock source

OMAP GP timers can have different input clocks that allow different PWM
frequencies. However, there is no other way of setting the clock source but
through clocks or clock-names properties of the timer itself. This limits
PWM functionality to only the frequencies allowed by the particular clock
source. Allowing setting the clock source by PWM rather than by timer
allows different PWMs to have different ranges by not hard-wiring the clock
source to the timer.

Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Acked-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Documentation/devicetree/bindings/pwm/pwm-omap-dmtimer.txt

@@ -9,6 +9,10 @@ Required properties:
 
 Optional properties:
 - ti,prescaler: Should be a value between 0 and 7, see the timers datasheet
+- ti,clock-source: Set dmtimer parent clock, values between 0 and 2:
+  - 0x00 - high-frequency system clock (timer_sys_ck)
+  - 0x01 - 32-kHz always-on clock (timer_32k_ck)
+  - 0x02 - external clock (timer_ext_ck, OMAP2 only)
 
 Example:
 	pwm9: dmtimer-pwm@9 {

drivers/pwm/pwm-omap-dmtimer.c

@@ -245,7 +245,7 @@ static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
 	struct pwm_omap_dmtimer_chip *omap;
 	struct pwm_omap_dmtimer_pdata *pdata;
 	pwm_omap_dmtimer *dm_timer;
-	u32 prescaler;
+	u32 v;
 	int status;
 
 	pdata = dev_get_platdata(&pdev->dev);
@@ -306,10 +306,12 @@ static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
 	if (pm_runtime_active(&omap->dm_timer_pdev->dev))
 		omap->pdata->stop(omap->dm_timer);
 
-	/* setup dmtimer prescaler */
-	if (!of_property_read_u32(pdev->dev.of_node, "ti,prescaler",
-				&prescaler))
-		omap->pdata->set_prescaler(omap->dm_timer, prescaler);
+	if (!of_property_read_u32(pdev->dev.of_node, "ti,prescaler", &v))
+		omap->pdata->set_prescaler(omap->dm_timer, v);
+
+	/* setup dmtimer clock source */
+	if (!of_property_read_u32(pdev->dev.of_node, "ti,clock-source", &v))
+		omap->pdata->set_source(omap->dm_timer, v);
 
 	omap->chip.dev = &pdev->dev;
 	omap->chip.ops = &pwm_omap_dmtimer_ops;