On 10/09/2021 06:33, Matt Roper wrote:
Our uncore MMIO functions for reading/writing registers have become very
complicated over time. There's significant macro magic used to generate
several nearly-identical functions that only really differ in terms of
which platform-specific shadow register table they should check on write
operations. We can significantly simplify our MMIO handlers by storing
a reference to the current platform's shadow table within the 'struct
intel_uncore' the same way we already do for forcewake; this allows us
to consolidate the multiple variants of each 'write' function down to
just a single 'fwtable' version that gets the shadow table out of the
uncore struct rather than hardcoding the name of a specific platform's
table. We can do similar consolidation on the MMIO read side by
creating a single-entry forcewake table to replace the open-coded range
check they had been using previously.
The final patch of the series adds a new shadow table for DG2; this
becomes quite clean and simple now, given the refactoring in the first
five patches.
Tidy and it ends up saving kernel binary size.
However I am undecided yet, because one thing to note is that the trade
off is source code and kernel text consolidation at the expense of more
indirect calls at runtime and larger common read/write functions.
To expand, current code generates a bunch of per gen functions but in
doing so it manages to inline a bunch of checks like NEEDS_FORCE_WAKE
and BSEARCH (from find_fw_domain) so at runtime each platform mmio
read/write does not have to do indirect calls to do lookups.
It may matter a lot in the grand scheme of things but this trade off is
something to note in the cover letter I think.
Regards,
Tvrtko
Matt Roper (6):
drm/i915/uncore: Convert gen6/gen7 read operations to fwtable
drm/i915/uncore: Associate shadow table with uncore
drm/i915/uncore: Replace gen8 write functions with general fwtable
drm/i915/uncore: Drop gen11/gen12 mmio write handlers
drm/i915/uncore: Drop gen11 mmio read handlers
drm/i915/dg2: Add DG2-specific shadow register table
drivers/gpu/drm/i915/intel_uncore.c | 190 ++++++++++--------
drivers/gpu/drm/i915/intel_uncore.h | 7 +
drivers/gpu/drm/i915/selftests/intel_uncore.c | 1 +
3 files changed, 110 insertions(+), 88 deletions(-)
