Re: [Xen-devel] [PATCH v4] xen/arm: Add a clock property

[Julien Grall <julien.grall@xxxxxxx>]

On 20/07/16 12:49, Geert Uytterhoeven wrote:
> Hi Julien,
>
> On Wed, Jul 20, 2016 at 1:01 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
> > On 20/07/16 10:43, Geert Uytterhoeven wrote:
> > > On Tue, Jul 12, 2016 at 9:46 AM, Dirk Behme <dirk.behme@xxxxxxxxxxxx>
> > > wrote:
> > > > Clocks described by this property are reserved for use by Xen, and the OS
> > > > must not alter their state any way, such as disabling or gating a clock,
> > > > or modifying its rate. Ensuring this may impose constraints on parent
> > > > clocks or other resources used by the clock tree.
> > > >
> > > > This property is used to proxy clocks for devices Xen has taken ownership
> > > > of, such as UARTs, for which the associated clock controller(s) remain
> > > > under the control of Dom0.
> > >
> > > I'm not familiar with using XEN at all, but I'm a bit puzzled...
> > >
> > > Can't you just add a clocks property to the (virtual) serial device node
> > > in DT?
> > > Then the (virtual) serial device driver can get and enable the clock?
> > There is no DT node for the Xen console (hvc). The UART used by Xen will be
> > completely removed from the Device tree.
> Why is it removed?
Because the device is used exclusively by Xen and DOM0 should not touch 
it at all (IRQs and MMIOs are not mapped).
Regards,

--
Julien Grall

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