drm/amd/display: Allocate zero bw after bw alloc enable

[Why]
During DP tunnel creation, CM preallocates BW and reduces
estimated BW of other DPIA. CM release preallocation only
when allocation is complete. Display mode validation logic
validates timings based on bw available per host router.
In multi display setup, this causes bw allocation failure
when allocation greater than estimated bw.

[How]
Do zero alloc to make the CM to release preallocation and
update estimated BW correctly for all DPIAs per host router.

Reviewed-by: PeiChen Huang <[email protected]>
Acked-by: Aurabindo Pillai <[email protected]>
Signed-off-by: Meenakshikumar Somasundaram <[email protected]>
Tested-by: Daniel Wheeler <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: Meenakshikumar Somasundaram

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_dpia_bw.c

@@ -270,7 +270,7 @@ static void set_usb4_req_bw_req(struct dc_link *link, int req_bw)
 
 	/* Error check whether requested and allocated are equal */
 	req_bw = requested_bw * (Kbps_TO_Gbps / link->dpia_bw_alloc_config.bw_granularity);
-	if (req_bw == link->dpia_bw_alloc_config.allocated_bw) {
+	if (req_bw && (req_bw == link->dpia_bw_alloc_config.allocated_bw)) {
 		DC_LOG_ERROR("%s: Request bw equals to allocated bw for link(%d)\n",
 			__func__, link->link_index);
 	}
@@ -341,6 +341,14 @@ bool link_dp_dpia_set_dptx_usb4_bw_alloc_support(struct dc_link *link)
 			ret = true;
 			init_usb4_bw_struct(link);
 			link->dpia_bw_alloc_config.bw_alloc_enabled = true;
+
+			/*
+			 * During DP tunnel creation, CM preallocates BW and reduces estimated BW of other
+			 * DPIA. CM release preallocation only when allocation is complete. Do zero alloc
+			 * to make the CM to release preallocation and update estimated BW correctly for
+			 * all DPIAs per host router
+			 */
+			link_dp_dpia_allocate_usb4_bandwidth_for_stream(link, 0);
 		}
 	}