[PATCH 01/13] drm/i915/cdclk: Fix CDCLK programming order when pipes are active

[Ville Syrjälä]

On Thu, Mar 28, 2024 at 09:16:06AM +0000, Murthy, Arun R wrote:
> 
> > -----Original Message-----
> > From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Ville
> > Syrjala
> > Sent: Wednesday, March 27, 2024 11:16 PM
> > To: intel-gfx at lists.freedesktop.org
> > Subject: [PATCH 01/13] drm/i915/cdclk: Fix CDCLK programming order when
> > pipes are active
> > 
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > Currently we always reprogram CDCLK from the
> > intel_set_cdclk_pre_plane_update() when using squahs/crawl.
> Typo squashs->squash
> 
> > The code only works correctly for the cd2x update or full modeset cases, and it
> > was simply never updated to deal with squash/crawl.
> > 
> > If the CDCLK frequency is increasing we must reprogram it before we do
> > anything else that might depend on the new higher frequency, and conversely
> > we must not decrease the frequency until everything that might still depend on
> > the old higher frequency has been dealt with.
> > 
> > Since cdclk_state->pipe is only relevant when doing a cd2x update we can't use
> > it to determine the correct sequence during squash/crawl. To that end
> > introduce cdclk_state->disable_pipes which simply indicates that we must
> > perform the update while the pipes are disable (ie. during
> > intel_set_cdclk_pre_plane_update()). Otherwise we use the same old vs. new
> > CDCLK frequency comparsiong as for cd2x updates.
> > 
> > The only remaining problem case is when the voltage_level needs to increase
> > due to a DDI port, but the CDCLK frequency is decreasing (and not all pipes are
> > being disabled). The current approach will not bump the voltage level up until
> > after the port has already been enabled, which is too late.
> > But we'll take care of that case separately.
> > 
> > v2: Don't break the "must disable pipes case"
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_cdclk.c | 15 +++++++++------
> > drivers/gpu/drm/i915/display/intel_cdclk.h |  3 +++
> >  2 files changed, 12 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c
> > b/drivers/gpu/drm/i915/display/intel_cdclk.c
> > index 31aaa9780dfc..619529dba095 100644
> > --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> > +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> > @@ -2600,7 +2600,6 @@ intel_set_cdclk_pre_plane_update(struct
> > intel_atomic_state *state)
> >  		intel_atomic_get_old_cdclk_state(state);
> >  	const struct intel_cdclk_state *new_cdclk_state =
> >  		intel_atomic_get_new_cdclk_state(state);
> > -	enum pipe pipe = new_cdclk_state->pipe;
> Looks like this cdclk_state->pipe is not more used in the driver and can it be removed?

It is still used for its primary purpose (cd2x update pipe select).

The only thing changing here is that we no longer use it as a
canary to indicate whether we need to do the cdclk programming
with pipes off or not.

-- 
Ville Syrjälä
Intel