Hi Mike,
Am Montag, den 24.11.2014, 23:07 -0800 schrieb Mike Turquette:
> Quoting Philipp Zabel (2014-11-03 01:31:18)
> > Some board designers, when running out of clock output pads, decide to
> > (mis)use PWM output pads to provide a clock to external components.
> > This driver supports this practice by providing an adapter between the
> > PWM and clock bindings in the device tree. As the PWM bindings specify
> > the period in the device tree, this is a fixed clock.
> >
> > Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> > ---
> > I'm resending this because last time the linux-pwm list was not in Cc:
> > So far I have not received any comments on the patch itself. I have used
> > it on a BoundaryDevices Nitrogen6X board to produce a master clock for
> > the OV5640 MIPI CSI-2 camera module.
> >
> > Changes since v1:
> > - none (rebased onto v3.18-rc3)
>
> Hi Philipp,
>
> Thanks for testing this. Is the Nitrogen6X board merged upstream? I'm OK
> with the patch but prefer to merge things when a consumer is ready to
> use it. I guess you are missing a patch to add the pwm-clock bits to the
> Nitrogen6X dts?
The Nitrogen6X board is merged upstream already, I used this dts patch
to register the clock:
diff --git a/arch/arm/boot/dts/imx6qdl-nitrogen6x.dtsi b/arch/arm/boot/dts/imx6qdl-nitrogen6x.dtsi
index 7628049..e2e7a22 100644
--- a/arch/arm/boot/dts/imx6qdl-nitrogen6x.dtsi
+++ b/arch/arm/boot/dts/imx6qdl-nitrogen6x.dtsi
@@ -130,6 +130,18 @@
power-supply = <®_3p3v>;
status = "okay";
};
+
+ mipi_mclk: mipi-mclk {
+ compatible = "pwm-clock";
+ clock-output-names = "mipi-mclk";
+ /* Note: since the PWM reference clock is 66 MHz, the highest
+ * possible frequency with 50% duty cycle smaller than 27 MHz
+ * is 16.5 MHz: <&pwm3 0 61>;
+ * But we can also do 22 MHz with 33% duty cycle:
+ */
+ pwms = <&pwm3 0 46>; /* 22 MHz */
+ #clock-cells = <0>;
+ };
};
&audmux {
--
2.1.1
regards
Philipp
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