Re: [PATCH] drm/i915: Simplify has_sagv

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

Em Seg, 2018-10-22 às 17:06 -0700, Rodrigo Vivi escreveu:
> On Mon, Oct 22, 2018 at 04:48:50PM -0700, Paulo Zanoni wrote:
> > Em Seg, 2018-10-22 às 09:57 -0700, Rodrigo Vivi escreveu:
> > > Let's add a platform has_sagv instead of having a full
> > > function that handle platform by platform.
> > > 
> > > The specially case for SKL for not controlled sagv
> > > is already taken care inside intel_enable_sagv, so there's
> > > no need to duplicate the check here.
> > > 
> > > v2: Go one step further and remove skl special case. (Jani)
> > > 
> > > v3: Separate runtime status handle from has_sagv flag. (Jani)
> > 
> > I know this has probably been discussed in the past and I missed it
> > (since I know this was done a few times for other things), but
> > how/why
> > is this approach better than the current one? Can you please write
> > it
> > in the commit message?
> 
> my bad... after stripping this out of my RFC series this got
> indeed out of context.
> 
> I'm trying to get rid of many platform codename checks spread
> around the code.
> 
> I believe we should do most of the decisions based on display_gen
> or has_feature. And use the platform codename as the last resource
> only when gen or feature cannot describe things better.

In terms of "describing things better", I don't see a lot of difference
between HAS_SOMETHING() and intel_has_something(). The
intel_has_something() version even already gives us a signal that maybe
the decision is made based on runtime information instead of being
simply per-platform, which is this case.

> 
> > Quickly checking the implementation of intel_has_sagv() seems much
> > easier than swimming through the nested macros of i915_pci.c. And
> > the 
> > special-caseness of the NOT_CONTROLLED case being restricted to
> > gen9 in
> > the current (non-patched) code also at first appears to be better
> > than
> > this proposal. But I'm totally willing to read your arguments and
> > reevaluate my decisions based on them, so please present them.
> 
> When you are looking only to a single feature this might be true.
> When you are looking to the platform itself consolidating the
> features
> definitions in a single place is easier to check legacy features and
> add new platforms.

So please make sure this is in the commit message. I may or may not
agree this is the best way to proceed, but at least now I can know why
it is the way it is when I git-blame/git-log.


> 
> Specially I'd like to add a new platform gen line gen++ without
> need to use any codename. Or without mixing things up.
> INTEL_GEN >= 11 || IS_CANNONLAKE :/

You can achieve this by redefining intel_has_sagv() instead of killing
it. Currently, our code assumes new platforms won't support sagv, but
that seems unlikely considering the recent history. Just invert it:

has_sagv() {
	if (is_gen9_lp || intel_gen < 9)
		return false;

	if (!is_skl)
		return true;

	return (status != controlled)
}


Note: I'm not blocking this patch.

> 
> So adding gen_n+1 should be as trivial
> as gen_n + 1 legacy...
> 
> > 
> > > 
> > > Cc: Jani Nikula <jani.nikula@intel.com>
> > > Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> > > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_drv.h          |  1 +
> > >  drivers/gpu/drm/i915/i915_pci.c          |  1 +
> > >  drivers/gpu/drm/i915/intel_device_info.h |  1 +
> > >  drivers/gpu/drm/i915/intel_pm.c          | 29 ++++++++--------
> > > ----
> > > ----
> > >  4 files changed, 13 insertions(+), 19 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > > b/drivers/gpu/drm/i915/i915_drv.h
> > > index 3017ef037fed..9b98ceb2d029 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.h
> > > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > > @@ -2650,6 +2650,7 @@ intel_info(const struct drm_i915_private
> > > *dev_priv)
> > >  #define HAS_DDI(dev_priv)		 ((dev_priv)-
> > > >info.has_ddi)
> > >  #define HAS_FPGA_DBG_UNCLAIMED(dev_priv) ((dev_priv)-
> > > > info.has_fpga_dbg)
> > > 
> > >  #define HAS_PSR(dev_priv)		 ((dev_priv)-
> > > >info.has_psr)
> > > +#define HAS_SAGV(dev_priv)		 ((dev_priv)-
> > > > info.has_sagv)
> > > 
> > >  
> > >  #define HAS_RC6(dev_priv)		 ((dev_priv)-
> > > >info.has_rc6)
> > >  #define HAS_RC6p(dev_priv)		 ((dev_priv)-
> > > > info.has_rc6p)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_pci.c
> > > b/drivers/gpu/drm/i915/i915_pci.c
> > > index 44e745921ac1..0b09155eab62 100644
> > > --- a/drivers/gpu/drm/i915/i915_pci.c
> > > +++ b/drivers/gpu/drm/i915/i915_pci.c
> > > @@ -465,6 +465,7 @@ static const struct intel_device_info
> > > intel_cherryview_info = {
> > >  	.has_csr = 1, \
> > >  	.has_guc = 1, \
> > >  	.has_ipc = 1, \
> > > +	.has_sagv = 1, \
> > >  	.ddb_size = 896
> > >  
> > >  #define SKL_PLATFORM \
> > > diff --git a/drivers/gpu/drm/i915/intel_device_info.h
> > > b/drivers/gpu/drm/i915/intel_device_info.h
> > > index af7002640cdf..e77c8b62783f 100644
> > > --- a/drivers/gpu/drm/i915/intel_device_info.h
> > > +++ b/drivers/gpu/drm/i915/intel_device_info.h
> > > @@ -117,6 +117,7 @@ enum intel_ppgtt {
> > >  	func(hws_needs_physical); \
> > >  	func(overlay_needs_physical); \
> > >  	func(supports_tv); \
> > > +	func(has_sagv); \
> > >  	func(has_ipc);
> > >  
> > >  #define GEN_MAX_SLICES		(6) /* CNL upper bound */
> > > diff --git a/drivers/gpu/drm/i915/intel_pm.c
> > > b/drivers/gpu/drm/i915/intel_pm.c
> > > index 67a4d0735291..7e38ed8421c7 100644
> > > --- a/drivers/gpu/drm/i915/intel_pm.c
> > > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > > @@ -3609,20 +3609,6 @@ static bool skl_needs_memory_bw_wa(struct
> > > intel_atomic_state *state)
> > >  	return false;
> > >  }
> > >  
> > > -static bool
> > > -intel_has_sagv(struct drm_i915_private *dev_priv)
> > > -{
> > > -	if (IS_KABYLAKE(dev_priv) || IS_COFFEELAKE(dev_priv) ||
> > > -	    IS_CANNONLAKE(dev_priv) || IS_ICELAKE(dev_priv))
> > > -		return true;
> > > -
> > > -	if (IS_SKYLAKE(dev_priv) &&
> > > -	    dev_priv->sagv_status != I915_SAGV_NOT_CONTROLLED)
> > > -		return true;
> > > -
> > > -	return false;
> > > -}
> > > -
> > >  /*
> > >   * SAGV dynamically adjusts the system agent voltage and clock
> > > frequencies
> > >   * depending on power and performance requirements. The display
> > > engine access
> > > @@ -3639,10 +3625,11 @@ intel_enable_sagv(struct drm_i915_private
> > > *dev_priv)
> > >  {
> > >  	int ret;
> > >  
> > > -	if (!intel_has_sagv(dev_priv))
> > > +	if (!HAS_SAGV(dev_priv))
> > >  		return 0;
> > >  
> > > -	if (dev_priv->sagv_status == I915_SAGV_ENABLED)
> > > +	if (dev_priv->sagv_status == I915_SAGV_ENABLED ||
> > > +	    dev_priv->sagv_status == I915_SAGV_NOT_CONTROLLED)
> > >  		return 0;
> > >  
> > >  	DRM_DEBUG_KMS("Enabling the SAGV\n");
> > > @@ -3676,10 +3663,11 @@ intel_disable_sagv(struct
> > > drm_i915_private
> > > *dev_priv)
> > >  {
> > >  	int ret;
> > >  
> > > -	if (!intel_has_sagv(dev_priv))
> > > +	if (!HAS_SAGV(dev_priv))
> > >  		return 0;
> > >  
> > > -	if (dev_priv->sagv_status == I915_SAGV_DISABLED)
> > > +	if (dev_priv->sagv_status == I915_SAGV_DISABLED ||
> > > +	    dev_priv->sagv_status == I915_SAGV_NOT_CONTROLLED)
> > >  		return 0;
> > >  
> > >  	DRM_DEBUG_KMS("Disabling the SAGV\n");
> > > @@ -3721,7 +3709,10 @@ bool intel_can_enable_sagv(struct
> > > drm_atomic_state *state)
> > >  	int level, latency;
> > >  	int sagv_block_time_us;
> > >  
> > > -	if (!intel_has_sagv(dev_priv))
> > > +	if (!HAS_SAGV(dev_priv))
> > > +		return false;
> > > +
> > > +	if (dev_priv->sagv_status == I915_SAGV_NOT_CONTROLLED)
> > >  		return false;
> > >  
> > >  	if (IS_GEN9(dev_priv))
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