[Intel-gfx] [RFC PATCH 0/3] vlv sideband refactoring

Jani Nikula jani.nikula at intel.com
Wed May 15 20:40:29 CEST 2013

Okay, I'm stuck with this a bit, and whichever approach I choose I
expect there to be a bunch of bikeshedding. So I won't polish this
further before comments.

Both the intel_dpio_{read,write} and valleyview_{punit,nc}_{read,write}
use the IOSF sideband interface. They access the same registers and do
mostly the same stuff, but no shared code. There are even duplicate
register defines for the same registers. Both have locking, but the
former use dpio_lock and the latter rps.hw_lock. It's racy.

These patches refactor the sideband access to a single function that
expects dpio_lock to be held. The dpio_lock is only used for sideband
stuff, so it's a better match than rps.hw_lock for the purpose. The rps
stuff still needs rps.hw_lock, since it's used to protect more than just
the register access, so rps code will need to hold both locks.

The bikeshedding department:

1) Do we need to propagate sideband errors from the functions (like the
   valleyview_punit_* functions do), or, since the return values are
   never checked anywhere anyway, can we just convert to the
   intel_dpio_* style (functions return the register value only) for all
   of them?

2) There will be quite a few more ports. Add new wrappers for each of
   them, or create generic read/write functions that need a port

3) Should the rps stuff take dpio_lock at a higher level than the
   wrappers? This is pretty much a requirement for the generic r/w

4) Does dpio really need a devfn different from the rest?

5) Your additional bikeshedding here. ;)


Jani Nikula (3):
  drm/i915: group vlv iosf sideband register accessors to a new file
  drm/i915: refactor all vlv sideband accessors to use one helper
  drm/i915: drop redundant warnings on not holding dpio_lock

 drivers/gpu/drm/i915/Makefile         |    1 +
 drivers/gpu/drm/i915/i915_reg.h       |   93 ++++++++++++-------------
 drivers/gpu/drm/i915/intel_display.c  |   37 ----------
 drivers/gpu/drm/i915/intel_dp.c       |    6 --
 drivers/gpu/drm/i915/intel_hdmi.c     |    4 --
 drivers/gpu/drm/i915/intel_pm.c       |   60 ----------------
 drivers/gpu/drm/i915/intel_sideband.c |  121 +++++++++++++++++++++++++++++++++
 7 files changed, 165 insertions(+), 157 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/intel_sideband.c


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