[Intel-gfx] [PATCH] drm/i915: Don't try to handle GuC when GuC is not supported.

[Daniel Vetter]

On Thu, Sep 22, 2016 at 04:55:07PM +0000, Vivi, Rodrigo wrote:
> On Wed, 2016-09-21 at 18:00 -0300, Paulo Zanoni wrote:
> > Em Qua, 2016-09-21 às 11:22 -0700, Rodrigo Vivi escreveu:
> > > Avoid any kind of GuC handling if GuC is not supported
> > > on a giving platform.
> > > 
> > > Besides being useless handling, our driver needs
> > > to be smarter than the user trying to use an invalid paramenter.
> > 
> > So the problem is when a platform doesn't support guc and the user
> > passes i915.enable_guc_something=1, right?
> 
> 1 is not a problem actually since it means "use if available". There is
> not firmware and execution continues.
> 
> 2 is the problem because it means "use guc or fail if not available".
> But platforms that don't have guc can't fail. driver needs to be smarter
> than that.

Not sure it needs to be smarter than that really, since all these debug
options auto-taint the kernel if you touch them. As in: You get to keep
all the pieces.

We can still do some auto-cleanup of modoptions ofc if there's a good need
for them.
-Daniel

> 
> > 
> > > 
> > > Cc: Jani Nikula <jani.nikula at intel.com>
> > > Cc: Anusha Srivatsa <anusha.srivatsa at intel.com>
> > > Cc: Christophe Prigent <christophe.prigent at intel.com>
> > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97573
> > > Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_guc_loader.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c
> > > b/drivers/gpu/drm/i915/intel_guc_loader.c
> > > index 6fd39ef..da0f5ed 100644
> > > --- a/drivers/gpu/drm/i915/intel_guc_loader.c
> > > +++ b/drivers/gpu/drm/i915/intel_guc_loader.c
> > > @@ -720,6 +720,13 @@ void intel_guc_init(struct drm_device *dev)
> > >  	struct intel_guc_fw *guc_fw = &dev_priv->guc.guc_fw;
> > >  	const char *fw_path;
> > >  
> > > +	if (!HAS_GUC(dev)) {
> > > +		i915.enable_guc_loading = 0;
> > > +		i915.enable_guc_submission = 0;
> > > +		fw_path = NULL;
> > > +		return;
> > > +	}
> > 
> > Instead of this, how about we just patch the code below with:
> > 
> > if (!HAS_GUC(dev_priv)) {
> > 	i915.enable_guc_loading = 0;
> > 	i915.enable_guc_submission = 0;
> > } else {
> > 	/* A negative value means "use platform default" */
> > 	if (i915.enable_guc_loading < 0)
> > 		i915.enable_guc_loading = HAS_GUC_UCODE(dev_priv);
> > 	if (i915.enable_guc_submission < 0)
> > 		i915.enable_guc_submission = HAS_GUC_SCHED(dev_priv);
> > }
> 
> yeap, this works as well. I just went for the simplest option that
> minimized at most any interactions for platforms where GuC simply
> doesn't exist.
> 
> > 
> > Or we could even go with our current "design pattern" and create
> > intel_sanitize_guc_options().
> 
> This is indeed a very good idea.
> 
> > 
> > This way we'll be able to avoid adding a second failure code path,
> > since we already have one for platforms with guc but options disabled.
> > 
> > 
> > > +
> > >  	/* A negative value means "use platform default" */
> > >  	if (i915.enable_guc_loading < 0)
> > >  		i915.enable_guc_loading = HAS_GUC_UCODE(dev);
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch