Re: [PATCH] hw/clock: Expose 'freq-hz' QOM property

[Philippe Mathieu-Daudé]

On 8/5/24 19:46, Peter Maydell wrote:

On Wed, 8 May 2024 at 15:13, Philippe Mathieu-Daudé <phi...@linaro.org> wrote:

Expose the clock frequency via the QOM 'freq-hz' property,
as it might be useful for QTests.

HMP example:

   $ qemu-system-mips -S -monitor stdio -M mipssim
   (qemu) qom-get /machine/cpu-refclk freq-hz
   12000000

Inspired-by: Inès Varhol <ines.var...@telecom-paris.fr>
Signed-off-by: Philippe Mathieu-Daudé <phi...@linaro.org>

So I have a couple of thoughts here:

(1) if this is intended for qtests, would exposing the period (i.e.
QOM equivalent of clock_get() rather than clock_get_hz()) be better?
A Hz figure has rounding so it's not as accurate.

Indeed, simpler to compare from QTest perspective.

(2) We should document this in clocks.rst; I guess we want to say
"only intended for use in qtests" (i.e. if you're part of QEMU
use the existing function interface, not this).

OK, and we can also only expose this for QTest using:

  if (qtest_enabled()) {
      object_property_add(obj, "[qtest-]clock-period", ...);
  }