[PATCH] drm/i915/cdclk: Rename intel_cdclk_needs_modeset to intel_cdclk_params_changed

[Ville Syrjälä]

On Fri, Feb 02, 2024 at 09:58:37PM +0200, Ville Syrjälä wrote:
> On Fri, Feb 02, 2024 at 10:12:08AM -0300, Gustavo Sousa wrote:
> > Looks like the name and description of intel_cdclk_needs_modeset()
> > became inacurate as of commit 59f9e9cab3a1 ("drm/i915: Skip modeset for
> > cdclk changes if possible"), when it became possible to update the cdclk
> > without requiring disabling the pipes when only changing the cd2x
> > divider was enough.
> > 
> > Later on we also added the same type of support with squash and crawling
> > with commit 25e0e5ae5610 ("drm/i915/display: Do both crawl and squash
> > when changing cdclk"), commit d4a23930490d ("drm/i915: Allow cdclk
> > squasher to be reconfigured live") and commit d62686ba3b54
> > ("drm/i915/adl_p: CDCLK crawl support for ADL").
> > 
> > As such, update that function's name and documentation to something more
> > appropriate, since the real checks for requiring modeset are done
> > elsewhere.
> > 
> > Signed-off-by: Gustavo Sousa <gustavo.sousa at intel.com>
> > ---
> > 
> > One thing worth noting here is that, with this change, we are left with an
> > awkward situation where two function names related to checking changes in cdclk:
> > 
> >   intel_cdclk_params_changed() and intel_cdclk_changed()
> > 
> > ,
> > 
> > and I find it weird that we have intel_cdclk_changed(), which checks for the
> > voltage level as well. Shouldn't the voltage level be a function of cdclk and
> > ddi clock? Why do we need that?
> > 
> >  drivers/gpu/drm/i915/display/intel_cdclk.c        | 15 +++++++--------
> >  drivers/gpu/drm/i915/display/intel_cdclk.h        |  4 ++--
> >  .../drm/i915/display/intel_display_power_well.c   |  4 ++--
> >  3 files changed, 11 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
> > index 26200ee3e23f..caadd880865f 100644
> > --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> > +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> > @@ -2233,17 +2233,16 @@ static bool intel_cdclk_can_squash(struct drm_i915_private *dev_priv,
> >  }
> >  
> >  /**
> > - * intel_cdclk_needs_modeset - Determine if changong between the CDCLK
> > - *                             configurations requires a modeset on all pipes
> > + * intel_cdclk_params_changed - Check whether CDCLK parameters changed
> >   * @a: first CDCLK configuration
> >   * @b: second CDCLK configuration
> >   *
> >   * Returns:
> > - * True if changing between the two CDCLK configurations
> > - * requires all pipes to be off, false if not.
> > + * True if parameters changed in a way that requires programming the CDCLK
> > + * and False otherwise.
> >   */
> > -bool intel_cdclk_needs_modeset(const struct intel_cdclk_config *a,
> > -			       const struct intel_cdclk_config *b)
> > +bool intel_cdclk_params_changed(const struct intel_cdclk_config *a,
> > +				const struct intel_cdclk_config *b)
> 
> The new name isn't very descriptive either.
> 
> Outside the cd2x/crawl/squash cases we stil have to consider
> two cases:
> 1. cdclk frequency/pll changes (voltage level can change or not)
> 2. cdclk frequency/pll doesn't change, but voltage level needs to change
> 
> And that difference is what intel_cdclk_needs_modeset() is trying
> convey. And intel_cdclk_changed() tells us whether anything at all
> is changing.

intel_cdclk_clock_changed() is perhaps the best name I can
think of, off the top of my head. But I'm notoriously bad at
naming things so take that with a pinch of salt.

-- 
Ville Syrjälä
Intel