drm/i915/xe2lpd: Support MDCLK:CDCLK ratio changes

Commit 394b4b7df9f7 ("drm/i915/lnl: Add CDCLK table") and commit
3d3696c0fed1 ("drm/i915/lnl: Start using CDCLK through PLL") started
adding support for CDCLK programming support for Xe2LPD. One final piece
is missing, which is the programming necessary for changed in the ratio
between MDCLK and CDCLK. Let's do that now.

BSpec instructs us to update MBUS_CTL and DBUF_CTL_S* registers when the
ratio between MDCLK and CDCLK changes. The updates must be done before
changing the CDCLK when decreasing the frequency; or after it when
increasing the frequency.

Ratio-related updates to MBUS_CTL also depend on the state of MBus
joining, so they are performed by either CDCLK change sequence or by
changes in MBus joining. Since one might happen independently of the
other, we need to make sure that both logics see the necessary state
values when programming that register. MBus joining logic needs to know
the MDCLK:CDCLK ratio and that's already provided via mdclk_cdclk_ratio
field of struct intel_dbuf_state.

For the CDCLK logic, we need to have something similar: we need to
propagate the status of MBus joining to struct intel_cdclk_state. Do
that by adding the field joined_mbus to struct intel_cdclk_config.
(Preferably, that field would be added to intel_cdclk_state, however
currently only intel_cdclk_config is passed down to the functions that
do the register programming. We might revisit this decision if we find
that refactoring the code to pass the whole intel_cdclk_state is worth
it.)

Bspec: 68864, 68868, 69090, 69482
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240312163639.172321-7-gustavo.sousa@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.h b/drivers/gpu/drm/i915/display/intel_cdclk.h
index 8e6e302bd599..e358234bfe26 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.h
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.h
@@ -18,6 +18,8 @@ struct intel_crtc_state;
 struct intel_cdclk_config {
 	unsigned int cdclk, vco, ref, bypass;
 	u8 voltage_level;
+	/* This field is only valid for Xe2LPD and above. */
+	bool joined_mbus;
 };
 
 struct intel_cdclk_state {
@@ -74,6 +76,7 @@ void intel_cdclk_get_cdclk(struct drm_i915_private *dev_priv,
 			   struct intel_cdclk_config *cdclk_config);
 int intel_cdclk_atomic_check(struct intel_atomic_state *state,
 			     bool *need_cdclk_calc);
+int intel_cdclk_state_set_joined_mbus(struct intel_atomic_state *state, bool joined_mbus);
 struct intel_cdclk_state *
 intel_atomic_get_cdclk_state(struct intel_atomic_state *state);