[Intel-gfx] [PATCH] drm/i915/gen9: fix error path in intel_init_workaround_bb

[Chris Wilson]

On Tue, Jun 23, 2015 at 06:58:42PM +0300, Imre Deak wrote:
> On ti, 2015-06-23 at 16:44 +0100, Chris Wilson wrote:
> > On Tue, Jun 23, 2015 at 06:18:21PM +0300, Imre Deak wrote:
> > > On ti, 2015-06-23 at 16:13 +0100, Siluvery, Arun wrote:
> > > > On 23/06/2015 15:36, Imre Deak wrote:
> > > > > On ti, 2015-06-23 at 15:31 +0100, Chris Wilson wrote:
> > > > >> On Tue, Jun 23, 2015 at 05:26:13PM +0300, Imre Deak wrote:
> > > > >>> On the GEN!=8 error path we call kmap_atomic() which returns in atomic
> > > > >>> context and then lrc_destroy_wa_ctx_obj() which can be called only in
> > > > >>> process context. Fix this by preserving the correct cleanup order on
> > > > >>> this error path.
> > > > >>>
> > > > >>> Also convert the WARN to DRM_ERROR the stack trace isn't really useful.
> > > > >>>
> > > > >>> Signed-off-by: Imre Deak <imre.deak at intel.com>
> > > > >>> ---
> > > > >>>   drivers/gpu/drm/i915/intel_lrc.c | 10 +++++++---
> > > > >>>   1 file changed, 7 insertions(+), 3 deletions(-)
> > > > >>>
> > > > >>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> > > > >>> index 1b50dd7..8bff1a2 100644
> > > > >>> --- a/drivers/gpu/drm/i915/intel_lrc.c
> > > > >>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> > > > >>> @@ -1289,10 +1289,14 @@ static int intel_init_workaround_bb(struct intel_engine_cs *ring)
> > > > >>>   		if (ret)
> > > > >>>   			goto out;
> > > > >>>   	} else {
> > > > >>> -		WARN(INTEL_INFO(ring->dev)->gen >= 8,
> > > > >>> -		     "WA batch buffer is not initialized for Gen%d\n",
> > > > >>> -		     INTEL_INFO(ring->dev)->gen);
> > > > >>> +		if (INTEL_INFO(ring->dev)->gen >= 8)
> > > > >>> +			DRM_ERROR("WA batch buffer is not initialized for Gen%d\n",
> > > > >>> +				  INTEL_INFO(ring->dev)->gen);
> > > > >>> +
> > > > >>
> > > > >> Do this test upfront, then we don't have multiple error paths.
> > > > >> http://paste.debian.net/255769
> > > > >
> > > > > I didn't bother moving it, I suppose GEN9 support will be added soon
> > > > > anyway and we get a bit more test coverage on GEN9 meanwhile. But if you
> > > > > insist I can move it.
> > > > 
> > > > Hi Imre,
> > > > 
> > > > I sent the following patch with the changes suggested by Chris.
> > > > https://patchwork.kernel.org/patch/6661891/
> > > > Since you sent it first, my patch can be ignored if your patch is updated.
> > > 
> > > I'm fine applying your patch, but I would ask to convert the WARN to
> > > DRM_ERROR. The stack trace doesn't add much to the error message and the
> > > WARN is needlessly verbose now on BXT,SKL..
> > 
> > I presumed Arun choose WARN because we are missing w/a and wanted
> > someone to step forward and prove the fixes?
> 
> Imo it's unnecessarily verbose, during development when loading the
> driver I know that things are mostly ok if I can't see any such
> backtraces. But no strong opinion, I can also change this locally.

An alternative would be to provide the stub wa_bb emission functions so
that future wa need only start with a plain copy'n'paste.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre