[RFC 00/10] powerpc/rtas: improved busy and extended delay status handling

[Nathan Lynch <nathanl@linux.ibm.com>]

This is an attempt at providing clearer names as discussed here:

https://github.com/linuxppc/issues/issues/164

as well as providing better behavior for RTAS_BUSY (-2) and small
extended delay values, which in my experience seem more common than
the larger ones. In testing PREEMPT_NONE kernels with CPUs busy, I see
the elapsed time for memory add operations roughly halved, while
memory remove operations' elapsed time shrinks by about ~25%. This is
achieved without significantly more time spent on CPU:

(- is before, + is after)

  Performance counter stats for 'drmgr -c mem -a -q 10' (10 runs):

-             1,898      probe:rtas_call           #    0.003 M/sec                    ( +-  2.20% )
-            751.57 msec task-clock                #    0.289 CPUs utilized            ( +-  1.56% )
+             1,969      probe:rtas_call           #    0.003 M/sec                    ( +-  2.69% )
+            766.20 msec task-clock                #    0.688 CPUs utilized            ( +-  1.99% )

-             2.605 +- 0.148 seconds time elapsed  ( +-  5.70% )
+            1.1129 +- 0.0660 seconds time elapsed  ( +-  5.93% )

  Performance counter stats for 'drmgr -c mem -r -q 10' (10 runs):

-               673      probe:rtas_call           #    0.002 M/sec                    ( +-  0.55% )
-            318.36 msec task-clock                #    0.234 CPUs utilized            ( +-  0.42% )
+               692      probe:rtas_call           #    0.002 M/sec                    ( +-  0.73% )
+            320.87 msec task-clock                #    0.309 CPUs utilized            ( +-  0.34% )

-             1.362 +- 0.100 seconds time elapsed  ( +-  7.37% )
+            1.0372 +- 0.0468 seconds time elapsed  ( +-  4.51% )

Questions / concerns / to do:
* I don't love the new API function names.
* Introduces three new APIs when two likely would suffice.
* Need to convert eeh_pseries and scanlog.
* rtas_busy_delay() and rtas_busy_delay_time() not yet removed.

Nathan Lynch (10):
  powerpc/rtas: new APIs for busy and extended delay statuses
  powerpc/rtas: do not schedule in rtas_os_term()
  powerpc/rtas-rtc: convert get-time-of-day to rtas_force_spin_if_busy()
  powerpc/rtas-rtc: convert set-time-of-day to rtas_sched_if_busy()
  powerpc/pseries/fadump: convert to rtas_sched_if_busy()
  powerpc/pseries/msi: convert to rtas_sched_if_busy()
  powerpc/pseries/iommu: convert to rtas_sched_if_busy()
  powerpc/pseries/dlpar: convert to rtas_sched_if_busy()
  powerpc/rtas: convert to rtas_sched_if_busy()
  powerpc/rtas_flash: convert to rtas_sched_if_busy()

 arch/powerpc/include/asm/rtas.h              |   4 +
 arch/powerpc/kernel/rtas-rtc.c               |  38 +---
 arch/powerpc/kernel/rtas.c                   | 178 ++++++++++++++++++-
 arch/powerpc/kernel/rtas_flash.c             |   4 +-
 arch/powerpc/platforms/pseries/dlpar.c       |   2 +-
 arch/powerpc/platforms/pseries/iommu.c       |   2 +-
 arch/powerpc/platforms/pseries/msi.c         |   4 +-
 arch/powerpc/platforms/pseries/rtas-fadump.c |  22 +--
 8 files changed, 190 insertions(+), 64 deletions(-)

-- 
2.30.2