[PATCH v2 0/4] clock: Get rid of clock_get_ns()

[Peter Maydell <peter.maydell@linaro.org>]

This patchseries makes some changes to the clock API:
 * Remove clock_get_ns()
 * Add clock_ticks_to_ns() to return number of nanoseconds
   it will take the clock to tick N times
 * clock_display_freq() to return prettily-formatted string
   for showing humans the approximate clock frequency

This is based on discussions we had about these APIs a little while
back.  The core driver here is that the clock objects internally
store the period in units of 2^-32 ns, so both clock_get_ns() and
clock_get_hz() are inherently returning a rounded-off result, which
can be badly inaccurate for fast clocks or if you want to multiply it
by a large tick count.

Ideally I'd like to get rid of clock_get_hz() as well, but
that looks trickier than handling clock_get_ns().

Patch 4 borrows a lot of the concept from one of Philippe's that he
sent out previously.

NB: tested with 'make check' and 'make check-acceptance' only.

Changes v1->v2:
 * In patch 1, saturate return value to INT64_MAX (and update
   docs to explain this and why)

Patches 2-4 have been reviewed, only patch 1 needs review.

thanks
-- PMM

Peter Maydell (4):
  clock: Introduce clock_ticks_to_ns()
  target/mips: Don't use clock_get_ns() in clock period calculation
  clock: Remove clock_get_ns()
  clock: Define and use new clock_display_freq()

 docs/devel/clocks.rst  | 51 ++++++++++++++++++++++++++++++++++++----
 include/hw/clock.h     | 53 +++++++++++++++++++++++++++++++++++++++---
 hw/core/clock.c        |  6 +++++
 softmmu/qdev-monitor.c |  6 ++---
 target/mips/cpu.c      |  4 ++--
 5 files changed, 108 insertions(+), 12 deletions(-)

-- 
2.20.1