Re: [Xen-devel] [PATCH v2] xen/arm: register clocks used by the hypervisor

[Julien Grall <julien.grall@xxxxxxx>]

On 05/07/16 14:54, Julien Grall wrote:
> On 05/07/16 14:53, Stefano Stabellini wrote:
> > On Thu, 30 Jun 2016, Dirk Behme wrote:
> > > +- clocks: one or more clocks to be registered.
> > > +  Xen hypervisor drivers might replace native drivers, resulting in
> > > +  clocks not registered by these native drivers. To avoid that these
> > > +  unregistered clocks are disabled, then, e.g. by clk_disable_unused(),
> > > +  register them in the hypervisor node.
> > > +  An example for this are the clocks of the serial driver. If the
> > > clocks
> > > +  used by the serial hardware interface are not registered by the
> > > serial
> > > +  driver the serial output might stop once clk_disable_unused() is
> > > called.
> > What if we use the "status" property of the clocks? Could we set it to
> > "disabled" in Xen? Would that be enough for Linux to leave them alone?
> clocks could be shared between multiple devices. So it is not possible
> to disable the clock.
To give an example, below the UART node for juno 
(arch/arm64/boot/dts/arm/juno-base.dtsi):
        soc_uart0: uart@7ff80000 {
                compatible = "arm,pl011", "arm,primecell";
                reg = <0x0 0x7ff80000 0x0 0x1000>;
                interrupts = <GIC_SPI 83 IRQ_TYPE_LEVEL_HIGH>;
                clocks = <&soc_uartclk>, <&soc_refclk100mhz>;
                clock-names = "uartclk", "apb_pclk";
        };

The clock soc_refclk100mhz is shared with the mailbox.

Regards,

--
Julien Grall

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