[Intel-gfx] [PATCH] drm/i915: Add relocation exceptions for two other platforms

[Zbigniew Kempczyński]

On Thu, Jun 10, 2021 at 10:36:12AM -0400, Rodrigo Vivi wrote:
> On Thu, Jun 10, 2021 at 12:39:55PM +0200, Zbigniew Kempczyński wrote:
> > We have established previously we stop using relocations starting
> > from gen12 platforms with Tigerlake as an exception. We keep this
> > statement but we want to enable relocations conditionally for
> > Rocketlake and Alderlake under require_force_probe flag set.
> > 
> > Keeping relocations under require_force_probe flag is interim solution
> > until IGTs will be rewritten to use softpin.
> 
> hmm... to be really honest I'm not so happy that we are introducing
> a new criteria to the force_probe.
> 
> The criteria was to have a functional driver and not to track uapi.
> 
> But on the other hand I do recognize that the current definition
> of the flag allows that, because we have established that with
> this behavior, the "driver for new Intel graphics devices that
> are recognized but not properly supported by this kernel version"
> (as stated in the Kconfig for the DRM_I915_FORCE_PROBE).
> 
> However...
> 
> > 
> > v2: - remove inline from function definition (Jani)
> >     - fix indentation
> > 
> > v3: change to GRAPHICS_VER() (Zbigniew)
> > 
> > Signed-off-by: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
> > Cc: Dave Airlie <airlied at redhat.com>
> > Cc: Daniel Vetter <daniel.vetter at intel.com>
> > Cc: Jason Ekstrand <jason at jlekstrand.net>
> > Acked-by: Dave Airlie <airlied at redhat.com>
> > ---
> >  .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 24 +++++++++++++++----
> >  1 file changed, 19 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> > index a8abc9af5ff4..30c4f0549ea0 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> > @@ -491,16 +491,30 @@ eb_unreserve_vma(struct eb_vma *ev)
> >  	ev->flags &= ~__EXEC_OBJECT_RESERVED;
> >  }
> >  
> > +static bool platform_has_relocs_enabled(const struct i915_execbuffer *eb)
> > +{
> > +	/*
> > +	 * Relocations are disallowed starting from gen12 with Tigerlake
> > +	 * as an exception. We allow temporarily use relocations for Rocketlake
> > +	 * and Alderlake when require_force_probe flag is set.
> > +	 */
> > +	if (GRAPHICS_VER(eb->i915) < 12 || IS_TIGERLAKE(eb->i915))
> > +		return true;
> > +
> > +	if (INTEL_INFO(eb->i915)->require_force_probe &&
> > +	    (IS_ROCKETLAKE(eb->i915)
> 
> This ship has sailed... RKL is not protected by this flag any longer.
> Should this be on the TGL side now?

+Lucas

I think no, RKL has relocations disabled so we cannot put it to TGL side.
So if RKL is already released then putting it under require_force_probe 
flag is wrong and only I can do is to remove it from that condition. 
There's no option to unblock RKL on IGT CI until we rewrite all the tests.
We have to rely then on ADL* with require_force_probe flag to check how
ADL will work with relocations. 

> 
> >  || IS_ALDERLAKE_S(eb->i915) ||
> > +	     IS_ALDERLAKE_P(eb->i915)))
> 
> How to ensure that we will easily catch this when removing the
> flag?
> 
> I mean, should we have a GEM_BUG or drm_err message when these
> platforms in this list has not the required_force_probe?

I don't think we need GEM_BUG()/drm_err() - when IGT tests will support
both - reloc + no-reloc - then condition will be limited to:

        if (GRAPHICS_VER(eb->i915) < 12 || IS_TIGERLAKE(eb->i915))
                return true;
 
        return false;

so require_force_probe condition will be deleted and we won't need it
anymore (IGTs will be ready).

--
Zbigniew

> 
> > +		return true;
> > +
> > +	return false;
> > +}
> > +
> >  static int
> >  eb_validate_vma(struct i915_execbuffer *eb,
> >  		struct drm_i915_gem_exec_object2 *entry,
> >  		struct i915_vma *vma)
> >  {
> > -	/* Relocations are disallowed for all platforms after TGL-LP.  This
> > -	 * also covers all platforms with local memory.
> > -	 */
> > -	if (entry->relocation_count &&
> > -	    GRAPHICS_VER(eb->i915) >= 12 && !IS_TIGERLAKE(eb->i915))
> > +	if (entry->relocation_count && !platform_has_relocs_enabled(eb))
> >  		return -EINVAL;
> >  
> >  	if (unlikely(entry->flags & eb->invalid_flags))
> > -- 
> > 2.26.0
> > 
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