Hi Julien,

On Wed, Jul 20, 2016 at 2:10 PM, Julien Grall [off-list ref] wrote:

On 20/07/16 12:49, Geert Uytterhoeven wrote:

quoted

On Wed, Jul 20, 2016 at 1:01 PM, Julien Grall [off-list ref]
wrote:

quoted

On 20/07/16 10:43, Geert Uytterhoeven wrote:

quoted

On Tue, Jul 12, 2016 at 9:46 AM, Dirk Behme [off-list ref]
wrote:

quoted

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).

IMHO then it's Xen's responsability to make sure not to disable the clock(s).

Who removes the device node from the DT? If Xen, can't it just remember
which clocks were present in removed device nodes?

What to do on SoCs where the serial device is part of a power area (e.g.
Renesas SH/R-Mobile)? Who will make sure it is not powered down?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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