[Intel-xe] [Intel-gfx] [PATCH v4] drm/i915: handle uncore spinlock when not available

[Coelho, Luciano]

On Wed, 2023-11-29 at 15:34 -0500, Rodrigo Vivi wrote:
> On Wed, Nov 29, 2023 at 03:24:33PM -0500, Coelho, Luciano wrote:
> > On Wed, 2023-11-29 at 13:01 -0500, Rodrigo Vivi wrote:
> > > On Wed, Nov 29, 2023 at 11:17:28AM +0200, Luca Coelho wrote:
> > > > The uncore code may not always be available (e.g. when we build the
> > > > display code with Xe), so we can't always rely on having the uncore's
> > > > spinlock.
> > > > 
> > > > To handle this, split the spin_lock/unlock_irqsave/restore() into
> > > > spin_lock/unlock() followed by a call to local_irq_save/restore() and
> > > > create wrapper functions for locking and unlocking the uncore's
> > > > spinlock.  In these functions, we have a condition check and only
> > > > actually try to lock/unlock the spinlock when I915 is defined, and
> > > > thus uncore is available.
> > > > 
> > > > This keeps the ifdefs contained in these new functions and all such
> > > > logic inside the display code.
> > > > 
> > > > Cc: Tvrtko Ursulin <tvrto.ursulin at intel.com>
> > > > Cc: Jani Nikula <jani.nikula at intel.com>
> > > > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > > > Cc: Ville Syrj?l? <ville.syrjala at linux.intel.com>
> > > > Signed-off-by: Luca Coelho <luciano.coelho at intel.com>
> > > > ---
> > > > 
> > > > In v2:
> > > > 
> > > >    * Renamed uncore_spin_*() to intel_spin_*()
> > > >    * Corrected the order: save, lock, unlock, restore
> > > > 
> > > > In v3:
> > > > 
> > > >    * Undid the change to pass drm_i915_private instead of the lock
> > > >      itself, since we would have to include i915_drv.h and that pulls
> > > >      in a truckload of other includes.
> > > > 
> > > > In v4:
> > > > 
> > > >    * After a brief attempt to replace this with a different patch,
> > > >      we're back to this one;
> > > >    * Pass drm_i195_private again, and move the functions to
> > > >      intel_vblank.c, so we don't need to include i915_drv.h in a
> > > >      header file and it's already included in intel_vblank.c;
> > > > 
> > > >  drivers/gpu/drm/i915/display/intel_display.h |  1 +
> > > >  drivers/gpu/drm/i915/display/intel_vblank.c  | 45 +++++++++++++++-----
> > > >  2 files changed, 36 insertions(+), 10 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/display/intel_display.h b/drivers/gpu/drm/i915/display/intel_display.h
> > > > index 8548f49e3972..5ff299bc4b87 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_display.h
> > > > +++ b/drivers/gpu/drm/i915/display/intel_display.h
> > > > @@ -29,6 +29,7 @@
> > > >  
> > > >  #include "i915_reg_defs.h"
> > > >  #include "intel_display_limits.h"
> > > > +#include "i915_drv.h"
> > > 
> > > please move this include to intel_vblank.c
> > 
> > Oops, this is a leftover of some tests I was making to see just how
> > much worse things would get by adding this here.
> > 
> > Actually, why don't we move the drm_i915_private structure (and maybe
> > others?) to a lighter header file than i915_drv.h? IMHO it's really
> > annoying to have the forward declarations for it in many places just
> > because we don't want to include the actual header.  When I want to
> > find its global definition, cscope always returns tens of results
> > because of the forward declarations... This is obviously orthogonal to
> > the current patch.
> 
> yeah, I know. It is really inconvenient sometimes. I got used to run
> cscope and then search for "struct something {" to find the right place.

That's what I do as well.  Actually, just searching for " {" in the
results usually suffices.  But anyway inconvenient.


> But this inconvenience is actually smaller when compared to the compilation
> time whenever a header gets modified and included by other headers. If I
> remember correctly Jani did the initial assessment of compilation times
> and started to move headers including out of other headers. He might
> have more details/data on his findings.

Okay, I'll talk to him.  But it's always nice to rant a bit in public,
so my blurt stands. :D

--
Cheers,
Luca.