Re: [Intel-gfx] [PATCH v4 06/10] drm/i915: Separate wakeref tracking

[Andrzej Hajda]

On 20.03.2023 00:57, Andi Shyti wrote:
> Hi Andrzej,
>
> On Mon, Mar 06, 2023 at 05:32:02PM +0100, Andrzej Hajda wrote:
> > From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> >
> > Extract the callstack tracking of intel_runtime_pm.c into its own
> > utility so that that we can reuse it for other online debugging of
> > scoped wakerefs.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
> > ---
> >   drivers/gpu/drm/i915/Kconfig.debug           |   9 ++
> >   drivers/gpu/drm/i915/Makefile                |   4 +
> >   drivers/gpu/drm/i915/intel_runtime_pm.c      | 222 +++----------------------
> >   drivers/gpu/drm/i915/intel_wakeref.h         |   2 +-
> >   drivers/gpu/drm/i915/intel_wakeref_tracker.c | 234 +++++++++++++++++++++++++++
> >   drivers/gpu/drm/i915/intel_wakeref_tracker.h |  52 ++++++
> >   6 files changed, 319 insertions(+), 204 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/Kconfig.debug b/drivers/gpu/drm/i915/Kconfig.debug
> > index 93dfb7ed970547..5fde52107e3b44 100644
> > --- a/drivers/gpu/drm/i915/Kconfig.debug
> > +++ b/drivers/gpu/drm/i915/Kconfig.debug
> > @@ -25,6 +25,7 @@ config DRM_I915_DEBUG
> >   	select PREEMPT_COUNT
> >   	select I2C_CHARDEV
> >   	select STACKDEPOT
> > +	select STACKTRACE
> >   	select DRM_DP_AUX_CHARDEV
> >   	select X86_MSR # used by igt/pm_rpm
> >   	select DRM_VGEM # used by igt/prime_vgem (dmabuf interop checks)
> > @@ -37,6 +38,7 @@ config DRM_I915_DEBUG
> >   	select DRM_I915_DEBUG_GEM
> >   	select DRM_I915_DEBUG_GEM_ONCE
> >   	select DRM_I915_DEBUG_MMIO
> > +	select DRM_I915_TRACK_WAKEREF
> >   	select DRM_I915_DEBUG_RUNTIME_PM
> >   	select DRM_I915_SW_FENCE_DEBUG_OBJECTS
> >   	select DRM_I915_SELFTEST
> > @@ -227,11 +229,18 @@ config DRM_I915_DEBUG_VBLANK_EVADE
> >   
> >   	  If in doubt, say "N".
> >   
> > +config DRM_I915_TRACK_WAKEREF
> > +	depends on STACKDEPOT
> > +	depends on STACKTRACE
> > +	bool
> > +
> >   config DRM_I915_DEBUG_RUNTIME_PM
> >   	bool "Enable extra state checking for runtime PM"
> >   	depends on DRM_I915
> >   	default n
> >   	select STACKDEPOT
> > +	select STACKTRACE
> > +	select DRM_I915_TRACK_WAKEREF
> >   	help
> >   	  Choose this option to turn on extra state checking for the
> >   	  runtime PM functionality. This may introduce overhead during
> > diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> > index b2f91a1f826858..42daff6d575a82 100644
> > --- a/drivers/gpu/drm/i915/Makefile
> > +++ b/drivers/gpu/drm/i915/Makefile
> > @@ -81,6 +81,10 @@ i915-$(CONFIG_DEBUG_FS) += \
> >   	i915_debugfs_params.o \
> >   	display/intel_display_debugfs.o \
> >   	display/intel_pipe_crc.o
> > +
> > +i915-$(CONFIG_DRM_I915_TRACK_WAKEREF) += \
> > +	intel_wakeref_tracker.o
> > +
>
> This patch, along with the previous one and two following it, is
> a bit confusing. We add this file only to remove it later and
> the code hops from file to file. There seem to be some extra
> steps that could be avoided.
>
> Is there room for simplification?

The reason behind this was that i915 had it's own tracker integrated 
with i915_runtime_pm, then it was abstracted out (05,06) to allow track 
gt->wakerefs (07) and then I proposed replacement of internal tracker 
with ref_tracker (09). I wanted to keep original history of development.
I can squash all/some of this work, but I am afraid it will generate 
less readable patches - now we have separated abstract-out and replace 
steps.

Probably sending patches 05-08 1st, then proposing conversion to 
ref_tracker in another patchset would make it more clear.

Regards
Andrzej


> Thanks,
> Andi