On Mon, 25 Jan 2016 23:46:30 +0100
Alban <albeu@xxxxxxx> wrote:
> On Sat, 23 Jan 2016 23:17:25 +0300
> Antony Pavlov <antonynpavlov@xxxxxxxxx> wrote:
>
> > This patch introduces devicetree for Atheros AR9331 SoC (AKA Hornet).
> > The AR9331 chip is a Wi-Fi System-On-Chip (WiSOC),
> > typically used in very cheap Access Points and Routers.
> >
> > Signed-off-by: Antony Pavlov <antonynpavlov@xxxxxxxxx>
> > Cc: Gabor Juhos <juhosg@xxxxxxxxxxx>
> > Cc: Alban Bedel <albeu@xxxxxxx>
> > Cc: linux-mips@xxxxxxxxxxxxxx
> > Cc: devicetree@xxxxxxxxxxxxxxx
> > ---
> > arch/mips/boot/dts/qca/ar9331.dtsi | 123 +++++++++++++++++++++++++++++++++++++
> > 1 file changed, 123 insertions(+)
> >
> > diff --git a/arch/mips/boot/dts/qca/ar9331.dtsi b/arch/mips/boot/dts/qca/ar9331.dtsi
> > new file mode 100644
> > index 0000000..bf128a2
> > --- /dev/null
> > +++ b/arch/mips/boot/dts/qca/ar9331.dtsi
> > @@ -0,0 +1,123 @@
> > +#include <dt-bindings/clock/ath79-clk.h>
> > +
> > +/ {
> > + compatible = "qca,ar9331";
> > +
>
> [...]
>
> > +
> > + extosc: oscillator {
> > + compatible = "fixed-clock";
> > + #clock-cells = <0>;
> > + };
>
> This oscillator is on the board and not in the SoC, so it should
> be in the board DTS.
However oscillator is inside SoC!
Please see https://en.wikipedia.org/wiki/Electronic_oscillator
An electronic oscillator is an electronic circuit that produces a periodic,
oscillating electronic signal, often a sine wave or a square wave.
Please see AR9331 data sheet: the SoC has no input for external oscillator,
only two pins (XTALO and XTALI) for connecting 25 MHz or 40 MHz quartz crystal.
The crystal can't produce a square wave itself! The crystal is only a part
of a complete oscillator.
So we have a good reason to put basic oscillator node into the SoC dtsi-file.
--
Best regards,
Antony Pavlov
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