Re: [PATCH 3/3] drm/i915: reorganize the get_cdclk assignment

[Paulo Zanoni <paulo.r.zanoni@intel.com>]

Em Ter, 2017-02-21 às 13:51 +0200, Ville Syrjälä escreveu:
> On Mon, Feb 20, 2017 at 05:00:42PM -0300, Paulo Zanoni wrote:
> > 
> > Possible problems of the current if-ladder:
> >   - It's a huge if ladder with almost a different check for each of
> >     our platforms.
> >   - It mixes 3 different types of checks: IS_GENX, IS_PLATFORM and
> >     IS_GROUP_OF_PLATFORMS.
> >   - As demonstrated by the recent IS_G4X commit, it's not easy to
> > be
> >     sure if a platform down on the list isn't also checked earlier.
> >   - As demonstrated by the WARN at the end, it's not easy to be
> > sure
> >     if we're actually checking for every single platform.
> > 
> > Possible advantages of the new switch statement:
> >   - It may be easier for the compiler to optimize stuff (I didn't
> >     check this), especially since the values are labels of an enum.
> >   - The compiler will tell us in case we miss some platform.
> >   - All platforms are explicitly there instead of maybe hidden in
> > some
> >     check for a certain group of platforms such as IS_GEN9_BC.
> > 
> > Possible disadvantages with the new code:
> >   - A few lines bigger.
> > 
> > v2: Don't unsort the list. Now the list almost matches the enum
> > definition, with the exception of CHV, KBL and GLK, which are
> > listed
> > along their predecessors (Ville).
> > 
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_cdclk.c | 105 +++++++++++++++++++++++
> > --------------
> >  1 file changed, 66 insertions(+), 39 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_cdclk.c
> > b/drivers/gpu/drm/i915/intel_cdclk.c
> > index 942adf0..e1921fe7 100644
> > --- a/drivers/gpu/drm/i915/intel_cdclk.c
> > +++ b/drivers/gpu/drm/i915/intel_cdclk.c
> > @@ -1762,49 +1762,76 @@ void intel_init_cdclk_hooks(struct
> > drm_i915_private *dev_priv)
> >  		dev_priv->display.calc_cdclk_state =
> > skl_calc_cdclk_state;
> >  	}
> >  
> > -	if (IS_GEN9_BC(dev_priv))
> > -		dev_priv->display.get_cdclk = skl_get_cdclk;
> > -	else if (IS_GEN9_LP(dev_priv))
> > -		dev_priv->display.get_cdclk = bxt_get_cdclk;
> > -	else if (IS_BROADWELL(dev_priv))
> > -		dev_priv->display.get_cdclk = bdw_get_cdclk;
> > -	else if (IS_HASWELL(dev_priv))
> > -		dev_priv->display.get_cdclk = hsw_get_cdclk;
> > -	else if (IS_VALLEYVIEW(dev_priv) ||
> > IS_CHERRYVIEW(dev_priv))
> > -		dev_priv->display.get_cdclk = vlv_get_cdclk;
> > -	else if (IS_GEN6(dev_priv) || IS_IVYBRIDGE(dev_priv))
> > +	switch (INTEL_INFO(dev_priv)->platform) {
> > +	case INTEL_PLATFORM_UNINITIALIZED:
> > +		MISSING_CASE(INTEL_INFO(dev_priv)->platform);
> > +		/* Fall through. */
> > +	case INTEL_I830:
> 
> The diff might come out nicer if you didn't reverse the list. Right
> now
> it's quite hard to read.

On the other hand, the labels in the switch statement match the enum
definition (with the exception of CHV/KBL/GLK). So IMHO this is an
"easier to review the patch now vs easier to review the code later"
problem. Still, I can change this, it won't hurt.

> 
> > 
> > +		dev_priv->display.get_cdclk =
> > fixed_133mhz_get_cdclk;
> > +		break;
> > +	case INTEL_I845G:
> > +		dev_priv->display.get_cdclk =
> > fixed_200mhz_get_cdclk;
> > +		break;
> > +	case INTEL_I85X:
> > +		dev_priv->display.get_cdclk = i85x_get_cdclk;
> > +		break;
> > +	case INTEL_I865G:
> > +		dev_priv->display.get_cdclk =
> > fixed_266mhz_get_cdclk;
> > +		break;
> > +	case INTEL_I915G:
> > +		dev_priv->display.get_cdclk =
> > fixed_333mhz_get_cdclk;
> > +		break;
> > +	case INTEL_I915GM:
> > +		dev_priv->display.get_cdclk = i915gm_get_cdclk;
> > +		break;
> > +	case INTEL_I945G:
> >  		dev_priv->display.get_cdclk =
> > fixed_400mhz_get_cdclk;
> > -	else if (IS_GEN5(dev_priv))
> > -		dev_priv->display.get_cdclk =
> > fixed_450mhz_get_cdclk;
> > -	else if (IS_GM45(dev_priv))
> > -		dev_priv->display.get_cdclk = gm45_get_cdclk;
> > -	else if (IS_G45(dev_priv))
> > +		break;
> > +	case INTEL_I945GM:
> > +		dev_priv->display.get_cdclk = i945gm_get_cdclk;
> > +		break;
> > +	case INTEL_G33:
> >  		dev_priv->display.get_cdclk = g33_get_cdclk;
> > -	else if (IS_I965GM(dev_priv))
> > -		dev_priv->display.get_cdclk = i965gm_get_cdclk;
> > -	else if (IS_I965G(dev_priv))
> > -		dev_priv->display.get_cdclk =
> > fixed_400mhz_get_cdclk;
> > -	else if (IS_PINEVIEW(dev_priv))
> > +		break;
> > +	case INTEL_PINEVIEW:
> >  		dev_priv->display.get_cdclk = pnv_get_cdclk;
> > -	else if (IS_G33(dev_priv))
> > +		break;
> > +	case INTEL_I965G:
> > +		dev_priv->display.get_cdclk =
> > fixed_400mhz_get_cdclk;
> > +		break;
> > +	case INTEL_I965GM:
> > +		dev_priv->display.get_cdclk = i965gm_get_cdclk;
> > +		break;
> > +	case INTEL_G45:
> >  		dev_priv->display.get_cdclk = g33_get_cdclk;
> > -	else if (IS_I945GM(dev_priv))
> > -		dev_priv->display.get_cdclk = i945gm_get_cdclk;
> > -	else if (IS_I945G(dev_priv))
> > +		break;
> > +	case INTEL_GM45:
> > +		dev_priv->display.get_cdclk = gm45_get_cdclk;
> > +		break;
> > +	case INTEL_IRONLAKE:
> > +		dev_priv->display.get_cdclk =
> > fixed_450mhz_get_cdclk;
> > +		break;
> > +	case INTEL_SANDYBRIDGE:
> > +	case INTEL_IVYBRIDGE:
> >  		dev_priv->display.get_cdclk =
> > fixed_400mhz_get_cdclk;
> > -	else if (IS_I915GM(dev_priv))
> > -		dev_priv->display.get_cdclk = i915gm_get_cdclk;
> > -	else if (IS_I915G(dev_priv))
> > -		dev_priv->display.get_cdclk =
> > fixed_333mhz_get_cdclk;
> > -	else if (IS_I865G(dev_priv))
> > -		dev_priv->display.get_cdclk =
> > fixed_266mhz_get_cdclk;
> > -	else if (IS_I85X(dev_priv))
> > -		dev_priv->display.get_cdclk = i85x_get_cdclk;
> > -	else if (IS_I845G(dev_priv))
> > -		dev_priv->display.get_cdclk =
> > fixed_200mhz_get_cdclk;
> > -	else { /* 830 */
> > -		WARN(!IS_I830(dev_priv),
> > -		     "Unknown platform. Assuming 133 MHz
> > CDCLK\n");
> > -		dev_priv->display.get_cdclk =
> > fixed_133mhz_get_cdclk;
> > +		break;
> > +	case INTEL_VALLEYVIEW:
> > +	case INTEL_CHERRYVIEW:
> > +		dev_priv->display.get_cdclk = vlv_get_cdclk;
> > +		break;
> > +	case INTEL_HASWELL:
> > +		dev_priv->display.get_cdclk = hsw_get_cdclk;
> > +		break;
> > +	case INTEL_BROADWELL:
> > +		dev_priv->display.get_cdclk = bdw_get_cdclk;
> > +		break;
> > +	case INTEL_SKYLAKE:
> > +	case INTEL_KABYLAKE:
> > +		dev_priv->display.get_cdclk = skl_get_cdclk;
> > +		break;
> > +	case INTEL_BROXTON:
> > +	case INTEL_GEMINILAKE:
> > +		dev_priv->display.get_cdclk = bxt_get_cdclk;
> > +		break;
> >  	}
> >  }
> > -- 
> > 2.7.4
> 
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