[Intel-gfx] [PATCH 2/3] drm/i915/: Initialise trans_min for skl_compute_transition_wm()

[Chris Wilson]

Quoting Rodrigo Vivi (2017-11-16 01:12:15)
> On Wed, Nov 15, 2017 at 10:50:35AM +0000, Chris Wilson wrote:
> > clang spots
> > 
> > drivers/gpu/drm/i915/intel_pm.c:4655:6: warning: variable 'trans_min' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
> >         if (INTEL_GEN(dev_priv) >= 10)
> > 
> > but fortunately for us we skip the function unless on a gen10+ device.
> > However, to keep the function generic in case we do want to re-enable it
> > for gen9 again, initialise trans_min to 0.
> 
> Based on this comment:  /* Transition WM are not recommended by HW team for GEN9 */
> 
> I believe the function should be called cnl_compute_transition_wm
> 
> plus:
> 
> -  uint16_t trans_min, trans_y_tile_min;
> +  u16 trans_min = 4, trans_y_tile_min;
> 
> -  if (INTEL_GEN(dev_priv) >= 10)
> -       trans_min = 4;
> 
> Also Wa for CNL A0 can be removed... We never put our hands in on A0...
> 
> But in case you want to go with the quick fix:
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>

This code still hasn't been fixed. At this rate I'll merge this patch
just to suppress the compiler warning... But please fix the code!
 
> up to you.
> 
> > 
> > References: ca47667f523e ("drm/i915/gen10: Calculate and enable transition WM")
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Mahesh Kumar <mahesh1.kumar at intel.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> > Cc: Jani Nikula <jani.nikula at linux.intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_pm.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index 8c69ec9eb6ee..5d8babfaec30 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -4649,6 +4649,7 @@ static void skl_compute_transition_wm(struct intel_crtc_state *cstate,
> >       if (!dev_priv->ipc_enabled)
> >               goto exit;
> >  
> > +     trans_min = 0;
> >       if (INTEL_GEN(dev_priv) >= 10)
> >               trans_min = 4;
> >  
> > -- 
> > 2.15.0
> > 
>