disp: msm: sde: fix crtc count based on layer mixer

Fix the max crtc count based on the number of real layer mixers
available. Usermode can use the crtc count to derive the number
of layer mixers. This will be used in usermode to check if a new
DP/IWE/WB session can be supported by the HW, based on the existing
displays at that point. This will avoid atomic_check validation
failures in driver.

Change-Id: I63b033604ac549fc01bccef2a9320e0befab5926
Signed-off-by: Veera Sundaram Sankaran <quic_veeras@quicinc.com>

msm/sde/sde_kms.c

@@ -2132,7 +2132,7 @@ static int _sde_kms_drm_obj_init(struct sde_kms *sde_kms)
 
 	u32 sspp_id[MAX_PLANES];
 	u32 master_plane_id[MAX_PLANES];
-	u32 num_virt_planes = 0;
+	u32 num_virt_planes = 0, dummy_mixer_count = 0;
 
 	if (!sde_kms || !sde_kms->dev || !sde_kms->dev->dev) {
 		SDE_ERROR("invalid sde_kms\n");
@@ -2153,7 +2153,11 @@ static int _sde_kms_drm_obj_init(struct sde_kms *sde_kms)
 	if (!_sde_kms_get_displays(sde_kms))
 		(void)_sde_kms_setup_displays(dev, priv, sde_kms);
 
-	max_crtc_count = min(catalog->mixer_count, priv->num_encoders);
+	for (i = 0; i < catalog->mixer_count; i++)
+		if (catalog->mixer[i].dummy_mixer)
+			dummy_mixer_count++;
+
+	max_crtc_count = catalog->mixer_count - dummy_mixer_count;
 
 	/* Create the planes */
 	for (i = 0; i < catalog->sspp_count; i++) {