[Intel-gfx] [PATCH v2 1/4] drm/i915/display: Program PIPE_MBUS_DBOX_CTL with adl-p values

["José Roberto de Souza" <jose.souza@intel.com>]

From: Caz Yokoyama <caz.yokoyama@intel.com>

B credits set by IFWI do not match with specification default, so here
programming the right value.

Also while at it, taking the oportunity to do a read-modify-write to
not overwrite all other bits in this register that specification don't
ask us to change.

BSpec: 49213
BSpec: 50343
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Caz Yokoyama <caz.yokoyama@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index dc6e21e4ef0b9..424cd7e9afe60 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -1830,13 +1830,19 @@ static void icl_pipe_mbus_enable(struct intel_crtc *crtc, bool joined_mbus)
 	enum pipe pipe = crtc->pipe;
 	u32 val;
 
+	val = intel_de_read(dev_priv, PIPE_MBUS_DBOX_CTL(pipe));
+	val &= ~MBUS_DBOX_A_CREDIT_MASK;
 	/* Wa_22010947358:adl-p */
 	if (IS_ALDERLAKE_P(dev_priv))
-		val = joined_mbus ? MBUS_DBOX_A_CREDIT(6) : MBUS_DBOX_A_CREDIT(4);
+		val |= joined_mbus ? MBUS_DBOX_A_CREDIT(6) : MBUS_DBOX_A_CREDIT(4);
 	else
-		val = MBUS_DBOX_A_CREDIT(2);
+		val |= MBUS_DBOX_A_CREDIT(2);
 
-	if (DISPLAY_VER(dev_priv) >= 12) {
+	val &= ~(MBUS_DBOX_BW_CREDIT_MASK | MBUS_DBOX_B_CREDIT_MASK);
+	if (IS_ALDERLAKE_P(dev_priv)) {
+		val |= MBUS_DBOX_BW_CREDIT(2);
+		val |= MBUS_DBOX_B_CREDIT(8);
+	} else if (DISPLAY_VER(dev_priv) >= 12) {
 		val |= MBUS_DBOX_BW_CREDIT(2);
 		val |= MBUS_DBOX_B_CREDIT(12);
 	} else {
-- 
2.35.1