drm/amdgpu: Fix discovery initialization failure during pci rescan

Waiting for system ready to fix the discovery initialization
failure issue. This failure usually occurs when dGPU is removed
and then rescanned via command line.
It's caused by following two errors:
[1] vram size is 0
[2] wrong binary signature
Signed-off-by: Ma Jun <Jun.Ma2@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c

@@ -255,7 +255,6 @@ static int amdgpu_discovery_read_binary_from_mem(struct amdgpu_device *adev,
 	uint64_t vram_size;
 	u32 msg;
 	int i, ret = 0;
-	int ip_discovery_ver = 0;
 
 	/* It can take up to a second for IFWI init to complete on some dGPUs,
 	 * but generally it should be in the 60-100ms range.  Normally this starts
@@ -265,17 +264,13 @@ static int amdgpu_discovery_read_binary_from_mem(struct amdgpu_device *adev,
 	 * continue.
 	 */
 
-	ip_discovery_ver = RREG32(mmIP_DISCOVERY_VERSION);
-	if ((dev_is_removable(&adev->pdev->dev)) ||
-	    (ip_discovery_ver == IP_DISCOVERY_V2) ||
-	    (ip_discovery_ver == IP_DISCOVERY_V4)) {
 	for (i = 0; i < 1000; i++) {
 		msg = RREG32(mmMP0_SMN_C2PMSG_33);
 		if (msg & 0x80000000)
 			break;
-			msleep(1);
-		}
+		usleep_range(1000, 1100);
 	}
+
 	vram_size = (uint64_t)RREG32(mmRCC_CONFIG_MEMSIZE) << 20;
 
 	if (vram_size) {