[Intel-gfx] [PATCH] drm/i915/bdw: Don't use forcewake needlessly

[Daniel Vetter]

On Tue, Dec 10, 2013 at 11:47:17AM -0800, Ben Widawsky wrote:
> On Tue, Dec 10, 2013 at 03:24:52PM +0200, ville.syrjala at linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > Not all registers need forcewake even if they're not shadowed.
> > Add the missing NEEDS_FORCE_WAKE() check to gen8_writeX() to
> > avoid needless forcewake usage when writing eg. display
> > registers.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> > I didn't test this at all, so be warned.
> > 
> >  drivers/gpu/drm/i915/intel_uncore.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> > index e63658e..78fe8d6 100644
> > --- a/drivers/gpu/drm/i915/intel_uncore.c
> > +++ b/drivers/gpu/drm/i915/intel_uncore.c
> > @@ -616,7 +616,8 @@ static bool is_gen8_shadowed(struct drm_i915_private *dev_priv, u32 reg)
> >  #define __gen8_write(x) \
> >  static void \
> >  gen8_write##x(struct drm_i915_private *dev_priv, off_t reg, u##x val, bool trace) { \
> > -	bool __needs_put = !is_gen8_shadowed(dev_priv, reg); \
> > +	bool __needs_put = NEEDS_FORCE_WAKE(dev_priv, reg) && \
> > +		!is_gen8_shadowed(dev_priv, reg); \
> >  	REG_WRITE_HEADER; \
> >  	if (__needs_put) { \
> >  		dev_priv->uncore.funcs.force_wake_get(dev_priv, \
> 
> I would prefer if this was simply checking the display offset, as
> opposed to NEEDS_FORCE_WAKE - since if someone adds to the macro we run
> the risk of a potentially hard to track down bug.

Yeah, I agree that an explicit check would be better since the forcewake
stuff works a bit different on gen8+
-Daniel

> 
> In any case, the patch is functionally correct, and I'd prefer the
> change, but up to you:
> Reviewed-by: Ben Widawsky <ben at bwidawsk.net>
> 
> > -- 
> > 1.8.3.2
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Ben Widawsky, Intel Open Source Technology Center
> _______________________________________________
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> Intel-gfx at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch