From: Caz Yokoyama <caz.yokoy...@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.ro...@intel.com>
Cc: Stanislav Lisovskiy <stanislav.lisovs...@intel.com>
Cc: Jani Nikula <jani.nik...@intel.com>
Signed-off-by: Caz Yokoyama <caz.yokoy...@intel.com>
Signed-off-by: José Roberto de Souza <jose.so...@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 3d2ff258f0a94..078ada041e1cd 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

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