Re: [igt-dev] [PATCH i-g-t 0/3] mmio_base via debugfs infrastructure + gem_ctx_isolation

[Dale B Stimson <dale.b.stimson@intel.com>]

My apologies for the multiple submissions of this patch series.  I had to
work out an issue with an unsuspected git config value in order to make the
references function with patchwork.


On 2020-02-12 14:34:28, Dale B Stimson wrote:
> This patch series provides infrastructure to allow determination of i915
> per-engine mmio_base (which is otherwise sometimes hard to get).  The provided
> method uses debugfs mmio_base information if present.  Otherwise, a default
> determination is provided when possible.  Also, gem_ctx_isolation is modified
> to use the new infrastructure.
> 
> For example, on TGL, gem_ctx_isolation (without these or similar changes)
> will fail for subtests that use engine vcs1.
> 
> The patches in this series are as they are intended to be submitted (subject
> to comments), except I would like to squash the two gem_ctx_isolation
> "relative registers" patches into one (as discussed below).  Also, function
> gem_engine_mmio_base_info_dump() could be removed.
> 
> On 2020-01-27, Chris wilson sent to the ML:
>   [igt-dev] [PATCH i-g-t 1/5] i915: Start putting the mmio_base to wider use
>   [igt-dev] [PATCH i-g-t 2/5] i915/gem_ctx_isolation: Check engine relative registers
> plus the following, which are not addressed here:
>   [igt-dev] [PATCH i-g-t 3/5] i915: Exercise preemption timeout controls in sysfs
>   [igt-dev] [PATCH i-g-t 4/5] i915: Exercise sysfs heartbeat controls
>   [igt-dev] [PATCH i-g-t 5/5] i915: Exercise timeslice sysfs property
> 
> This patch list is:
>   i915/gem_mmio_base.c - get mmio_base from debugfs (if possible)
>   i915/gem_ctx_isolation: Check engine relative registers
>   i915/gem_ctx_isolation: Check engine relative registers - Part 2
> 
> The first 2020-01-27 patch obtains mmio_base information via sysfs, and depends
> on a proposed kernel change that would provide the mmio_base information
> via sysfs.  It is unclear when or whether that kernel change will progress.
> 
> The mmio_base information used by this patch series is available through
> debugfs now (as of kernel 5.4).  If the per-engine mmio_base information is
> ever added to sysfs, it would be easy to plug that into the infrastructure
> proposed here as an additional higher-priority source of that information.
> 
> This submission replaces the first patch (switching from sysfs to debugfs),
> retains the second 2020-01-27 patch
>   i915/gem_ctx_isolation: Check engine relative registers
> and has a third patch that modifies the original second patch to support the
> altered API:
>   i915/gem_ctx_isolation: Check engine relative registers - Part 2
> 
> I propose squashing the two gem_ctx_isolation "relative registers" patches
> into one patch with author == "Chris Wilson" if Chris agrees.
> 
> Some differences from the 2020-01-27 patches:
> 
> The mmio_base information is fetched once into local data structures, and
> is obtained from them thereafter instead of being fetched from the kernel
> everytime it is wanted.
> 
> The function that obtains the mmio_base information is called by a particular
> test that wants it, and returns a handle through which the mmio_base can be
> requested for any particular engine.
> 
> These patches introduce new source files lib/i915/gem_mmio_base.c
> and lib/i915/gem_mmio_base.h.  Should the code instead be placed into
> lib/i915/gem_engine_topology.c?
> 
> Function gem_engine_mmio_base_info_dump presently exists to dump the
> mmio_base information to stdout for debugging or informational purposes.
> This function is not currently called.  I presume this function should
> be removed.  Is there any desire to keep it around for future use?
> 
> The 2020-01-27 patches define function gem_engine_mmio_base() with its first
> parameter as "fd".  The new patches replace the first parameter with the
> mmio_base object handle.
> 
> Chris Wilson (1):
>   i915/gem_ctx_isolation: Check engine relative registers
> 
> Dale B Stimson (2):
>   i915/gem_mmio_base.c - get mmio_base from debugfs (if possible)
>   i915/gem_ctx_isolation: Check engine relative registers - Part 2
> 
>  lib/Makefile.sources           |   2 +
>  lib/i915/gem_mmio_base.c       | 346 +++++++++++++++++++++++++++++++++
>  lib/i915/gem_mmio_base.h       |  19 ++
>  lib/igt.h                      |   1 +
>  lib/meson.build                |   1 +
>  tests/i915/gem_ctx_isolation.c | 229 +++++++++++++---------
>  6 files changed, 506 insertions(+), 92 deletions(-)
>  create mode 100644 lib/i915/gem_mmio_base.c
>  create mode 100644 lib/i915/gem_mmio_base.h
> 
> -- 
> 2.25.0
> 
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