[PATCH 4/4] drm/i915: Implement vblank synchronized MBUS join changes
Lisovskiy, Stanislav
stanislav.lisovskiy at intel.com
Fri Mar 22 07:48:52 UTC 2024
On Thu, Mar 21, 2024 at 03:00:53PM +0200, Ville Syrjälä wrote:
> On Thu, Mar 21, 2024 at 02:43:49PM +0200, Lisovskiy, Stanislav wrote:
> > On Thu, Mar 21, 2024 at 02:16:59PM +0200, Ville Syrjälä wrote:
> > > On Thu, Mar 21, 2024 at 10:40:37AM +0200, Lisovskiy, Stanislav wrote:
> > > > On Wed, Mar 20, 2024 at 11:08:54PM +0200, Ville Syrjälä wrote:
> > > > > On Wed, Mar 20, 2024 at 08:54:09PM +0200, Lisovskiy, Stanislav wrote:
> > > > > > On Wed, Mar 20, 2024 at 06:36:31PM +0200, Ville Syrjälä wrote:
> > > > > > > On Wed, Mar 20, 2024 at 10:28:06AM +0200, Stanislav Lisovskiy wrote:
> > > > > > > > Currently we can't change MBUS join status without doing a modeset,
> > > > > > > > because we are lacking mechanism to synchronize those with vblank.
> > > > > > > > However then this means that we can't do a fastset, if there is a need
> > > > > > > > to change MBUS join state. Fix that by implementing such change.
> > > > > > > > We already call correspondent check and update at pre_plane dbuf update,
> > > > > > > > so the only thing left is to have a non-modeset version of that.
> > > > > > > > If active pipes stay the same then fastset is possible and only MBUS
> > > > > > > > join state/ddb allocation updates would be committed.
> > > > > > > >
> > > > > > > > v2: Implement additional changes according to BSpec.
> > > > > > > > Vblank wait is needed after MBus/Dbuf programming in case if
> > > > > > > > no modeset is done and we are switching from single to multiple
> > > > > > > > displays, i.e mbus join state switches from "joined" to "non-joined"
> > > > > > > > state. Otherwise vblank wait is not needed according to spec.
> > > > > > > >
> > > > > > > > v3: Split mbus and dbox programming into to pre/post plane update parts,
> > > > > > > > how it should be done according to BSpec.
> > > > > > > >
> > > > > > > > v4: - Place "single display to multiple displays scenario" MBUS/DBOX programming
> > > > > > > > after DDB reallocation, but before crtc enabling(that is where is has
> > > > > > > > to be according to spec).
> > > > > > > > - Check if crtc is still active, not only the old state.
> > > > > > > > - Do a vblank wait if MBUX DBOX register was modified.
> > > > > > > > - And of course do vblank wait only if crtc was active.
> > > > > > > > - Do vblank wait only if we are not doing a modeset, if we are doing
> > > > > > > > something before *commit_modeset_enables, because all crtcs might be
> > > > > > > > disabled at this moment, so we will get WARN if try waiting for vblank
> > > > > > > > then.
> > > > > > > > - Still getting FIFO underrun so try waiting for vblank in pre_plane update
> > > > > > > > as well.
> > > > > > > > - Write also pipe that we need to sync with to MBUS_CTL register.
> > > > > > > >
> > > > > > > > v5: - Do vblank wait only for the first pipe, if mbus is joined
> > > > > > > > - Check also if new/old_dbuf_state is not NULL, before getting single pipe
> > > > > > > > and active pipes.
> > > > > > > >
> > > > > > > > v6: - Add pre/post ddb call sites for doing mbus/mbox updates for switching
> > > > > > > > between single/multiple displays(Ville Syrjälä)
> > > > > > > > - When writing MBUS_CTL check if synced pipe is enabled, otherwise use
> > > > > > > > PIPE_NONE sync option(Ville Syrjälä)
> > > > > > > > - Use for_each_crtc_in_pipe_mask to go through all active pipes, not
> > > > > > > > just ones in state, when updating mbox registers(Ville Syrjälä)
> > > > > > > > - Improve checks for switching between multiple <=> single displays
> > > > > > > >
> > > > > > > > v7: - Extract sync pipe calculation to separate function(Ville Syrjälä)
> > > > > > > > - Removed redundant loop over crtc in post ddb call site(Ville Syrjälä)
> > > > > > > > - Use old_dbuf_state to determine synced pipe when switching to multiple
> > > > > > > > displays in post ddb call site(Ville Syrjälä)
> > > > > > > > - Removed num_active_pipes checks and use joined_mbus only(Ville Syrjälä)
> > > > > > > > - Extracted dbox update change to separate patch(Ville Syrjälä)
> > > > > > > > - Added handling for the case, when mbus_joined state didn't change
> > > > > > > > (Ville Syrjälä)
> > > > > > > >
> > > > > > > > v8: - Removed redundant comments(Ville Syrjälä)
> > > > > > > > - Pass dbuf_state to intel_dbuf_mbus_join_update instead of pipe(Ville Syrjälä)
> > > > > > > > - Moved non-changed mbus_join logic from pre_plane to post_ddb hook(Ville Syrjälä)
> > > > > > > >
> > > > > > > > Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> > > > > > > > ---
> > > > > > > > drivers/gpu/drm/i915/display/intel_display.c | 6 +-
> > > > > > > > drivers/gpu/drm/i915/display/skl_watermark.c | 106 +++++++++++++++----
> > > > > > > > drivers/gpu/drm/i915/display/skl_watermark.h | 2 +
> > > > > > > > 3 files changed, 90 insertions(+), 24 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> > > > > > > > index b88f214e111ae..d5351f6fa2eb4 100644
> > > > > > > > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > > > > > > > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > > > > > > > @@ -6895,6 +6895,8 @@ static void skl_commit_modeset_enables(struct intel_atomic_state *state)
> > > > > > > > intel_pre_update_crtc(state, crtc);
> > > > > > > > }
> > > > > > > >
> > > > > > > > + intel_dbuf_mbus_pre_ddb_update(state);
> > > > > > > > +
> > > > > > > > while (update_pipes) {
> > > > > > > > for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
> > > > > > > > new_crtc_state, i) {
> > > > > > > > @@ -6925,6 +6927,8 @@ static void skl_commit_modeset_enables(struct intel_atomic_state *state)
> > > > > > > > }
> > > > > > > > }
> > > > > > > >
> > > > > > > > + intel_dbuf_mbus_post_ddb_update(state);
> > > > > > > > +
> > > > > > > > update_pipes = modeset_pipes;
> > > > > > > >
> > > > > > > > /*
> > > > > > > > @@ -7169,9 +7173,7 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
> > > > > > > > }
> > > > > > > >
> > > > > > > > intel_encoders_update_prepare(state);
> > > > > > > > -
> > > > > > > > intel_dbuf_pre_plane_update(state);
> > > > > > > > - intel_mbus_dbox_update(state);
> > > > > > > >
> > > > > > > > for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
> > > > > > > > if (new_crtc_state->do_async_flip)
> > > > > > > > diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c b/drivers/gpu/drm/i915/display/skl_watermark.c
> > > > > > > > index 2207ecd2605c2..4c1c2f558e3e7 100644
> > > > > > > > --- a/drivers/gpu/drm/i915/display/skl_watermark.c
> > > > > > > > +++ b/drivers/gpu/drm/i915/display/skl_watermark.c
> > > > > > > > @@ -4,6 +4,7 @@
> > > > > > > > */
> > > > > > > >
> > > > > > > > #include <drm/drm_blend.h>
> > > > > > > > +#include <drm/drm_print.h>
> > > > > > > >
> > > > > > > > #include "i915_drv.h"
> > > > > > > > #include "i915_fixed.h"
> > > > > > > > @@ -2636,13 +2637,6 @@ skl_compute_ddb(struct intel_atomic_state *state)
> > > > > > > > if (ret)
> > > > > > > > return ret;
> > > > > > > >
> > > > > > > > - if (old_dbuf_state->joined_mbus != new_dbuf_state->joined_mbus) {
> > > > > > > > - /* TODO: Implement vblank synchronized MBUS joining changes */
> > > > > > > > - ret = intel_modeset_all_pipes_late(state, "MBUS joining change");
> > > > > > > > - if (ret)
> > > > > > > > - return ret;
> > > > > > > > - }
> > > > > > > > -
> > > > > > > > drm_dbg_kms(&i915->drm,
> > > > > > > > "Enabled dbuf slices 0x%x -> 0x%x (total dbuf slices 0x%x), mbus joined? %s->%s\n",
> > > > > > > > old_dbuf_state->enabled_slices,
> > > > > > > > @@ -3594,30 +3588,49 @@ static void intel_dbuf_mdclk_min_tracker_update(struct intel_atomic_state *state
> > > > > > > > new_dbuf_state->joined_mbus);
> > > > > > > > }
> > > > > > > >
> > > > > > > > +static enum pipe intel_dbuf_get_sync_pipe(const struct intel_dbuf_state *dbuf_state)
> > > > > > > > +{
> > > > > > > > + return ffs(dbuf_state->active_pipes) - 1;
> > > > > > > > +}
> > > > > > > > +
> > > > > > > > /*
> > > > > > > > * Configure MBUS_CTL and all DBUF_CTL_S of each slice to join_mbus state before
> > > > > > > > * update the request state of all DBUS slices.
> > > > > > > > */
> > > > > > > > -static void intel_dbuf_mbus_join_update(struct intel_atomic_state *state)
> > > > > > > > +static void intel_dbuf_mbus_join_update(struct intel_atomic_state *state,
> > > > > > > > + const struct intel_dbuf_state *dbuf_state)
> > > > > > > > {
> > > > > > > > struct drm_i915_private *i915 = to_i915(state->base.dev);
> > > > > > > > u32 mbus_ctl;
> > > > > > > > const struct intel_dbuf_state *new_dbuf_state =
> > > > > > > > intel_atomic_get_new_dbuf_state(state);
> > > > > > > > + struct intel_crtc *crtc;
> > > > > > > > + struct intel_crtc_state *new_crtc_state;
> > > > > > > > + u32 pipe_select;
> > > > > > > > + enum pipe sync_pipe;
> > > > > > > >
> > > > > > > > if (!HAS_MBUS_JOINING(i915))
> > > > > > > > return;
> > > > > > > >
> > > > > > > > + sync_pipe = intel_dbuf_get_sync_pipe(dbuf_state);
> > > > > > > > + crtc = intel_crtc_for_pipe(i915, sync_pipe);
> > > > > > > > + new_crtc_state = intel_atomic_get_new_crtc_state(state, crtc);
> > > > > > > > +
> > > > > > > > + if (new_crtc_state && !intel_crtc_needs_modeset(new_crtc_state))
> > > > > > > > + pipe_select = MBUS_JOIN_PIPE_SELECT(sync_pipe);
> > > > > > > > + else
> > > > > > > > + pipe_select = MBUS_JOIN_PIPE_SELECT_NONE;
> > > > > > >
> > > > > > > As I said before, that stuff should be a separate function
> > > > > > > that the pre/post ddb update things can call with the proper
> > > > > > > arguments. Trying to shoehorn it into this function whose
> > > > > > > only job should be to write the MBUS_CTL is not a good idea.
> > > > > >
> > > > > > That previous comment from you, I interpreted that I return the pipe
> > > > > > instead of pipe select.
> > > > > > In previous revision I already had this as a function:
> > > > > >
> > > > > > >> + crtc = intel_crtc_for_pipe(i915, sync_pipe);
> > > > > > >> + new_crtc_state = intel_atomic_get_new_crtc_state(state, crtc);
> > > > > > >> +
> > > > > > >> + if (new_crtc_state && !intel_crtc_needs_modeset(new_crtc_state))
> > > > > > >> + pipe_select = MBUS_JOIN_PIPE_SELECT(sync_pipe);
> > > > > > >> + else
> > > > > > >> + pipe_select = MBUS_JOIN_PIPE_SELECT_NONE;
> > > > > > >> +
> > > > > > >> + return pipe_select;
> > > > > >
> > > > > > > I would return an enum pipe from here, and leave it up to the
> > > > > > > caller to deal with whatever is needed to stuff it into the register.
> > > > > > > Isolates the implementation from changes in the register layout/etc.
> > > > > >
> > > > > > Also I don't get why can't we calculate PIPE_SELECT mask in a function,
> > > > > > which is the only place where it is calculated.
> > > > >
> > > > > You also need it for the vblank wait in the caller. Right now
> > > > > you're calculating it in two or three different places and
> > > > > a bit differently in each case. We want a single function that
> > > > > does the right thing every time.
> > > >
> > > > For vblank wait I need just pipe, which I was getting in previous
> > > > revision with intel_dbuf_get_sync_pipe, now it is hidden into
> > > > mbus_join_update, in prev revision it was used from ddb hooks, as you suggest now.
> > > >
> > > > But here we are talking about where pipe_select is constructed.
> > > > If I would be returning pipe with mbus_joined_pipe, as you suggest,
> > > > then someone must construct pipe_select.
> > >
> > > Either you can just do
> > > if (pipe == INVALID)
> > > mbus_ctl |= PIPE_SELECT_NONE;
> > > else
> > > mbus_ctl |= PIPE_SELECT(pipe);
> > >
> > > or you put that into a small helper ala. bxt_cdclk_cd2x_pipe().
> > >
> > > The point is that no one outside the mbus_update() function needs
> > > to know about the details of MBUS_CTL, but they do need to know the
> > > correct pipe, hence have a single function to determine the pipe and
> > > pass it around where needed.
> > >
> > > > Above you commented that
> > > > you would return "just pipe" in leave constructing to caller(i.e mbus_join func).
> > > >
> > > > Should this be also one more function or doing it inside mbus_join programming
> > > > function(what I do now) is fine?
> > > > I'm fine with both.
> > > >
> > > > >
> > > > > > We are anyway constructing
> > > > > > what we are writing to mbus_ctl here.
> > > > > > Ok, I will change it since I probably got no other choice to get this reviewed :)
> > > > > >
> > > > > > Is that all what has to be changed or there is something else besides?
> > > > > > I don't see a point in sending another revision, if that's not the final
> > > > > > list of things to fix.
> > > > >
> > > > > The way I see these should look more or less is:
> > > > >
> > > > > mbus_joined_pipe(dbuf_state)
> > > > > {
> > > > > pipe = ffs(dbuf_state->active_pipes) - 1;
> > > > >
> > > > > drm_WARN_ON(!dbuf_state->join);
> > > > > drm_WARN_ON(!is_pot(dbuf_state->active_pipes));
> > > > >
> > > > > if (needs_modeset)
> > > > > return INVALID;
> > > > > else
> > > > > return pipe;
> > > > > }
> > > >
> > > > But that is almost exactly how it was done in previous revision,
> > > > it was intel_dbuf_get_sync_pipe.
> > >
> > > I have not seen any version with a function like that.
> >
> > intel_dbuf_get_sync_pipe is defined in that revision as well.
> > It is lacking both WARNS though and doesn't return invalid
> > pipe, but I didn't want to add WARNS here because if you
> > ever try to get a sync pipe using non-joined dbuf_state,
> > both will trigger.
> > Also I thought "needs_modeset" is another level of hierarchy,
> > probably we shouldn't try calling that function in that case at all.
>
>
> The whole point of the warns and such is to make sure we don't use this
> in the wrong context. It is only to be used when we are changing
> mbus_join.
I was thinking more of those like sanity check. But of course if we think
of this function, only supposed to be invoked with joined dbuf_state only,
then yes, makes sense.
>
> --
> Ville Syrjälä
> Intel
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