drm/amd/powerplay: maintain SMU FW backward compatibility

Do not halt driver loading on if_version mismatch. As our
driver and FWs are backward compatible.
Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/powerplay/smu_v11_0.c

@@ -261,14 +261,20 @@ static int smu_v11_0_check_fw_version(struct smu_context *smu)
 	smu_minor = (smu_version >> 8) & 0xff;
 	smu_debug = (smu_version >> 0) & 0xff;
 
-
+	/*
+	 * 1. if_version mismatch is not critical as our fw is designed
+	 * to be backward compatible.
+	 * 2. New fw usually brings some optimizations. But that's visible
+	 * only on the paired driver.
+	 * Considering above, we just leave user a warning message instead
+	 * of halt driver loading.
+	 */
 	if (if_version != smu->smc_if_version) {
 		pr_info("smu driver if version = 0x%08x, smu fw if version = 0x%08x, "
 			"smu fw version = 0x%08x (%d.%d.%d)\n",
 			smu->smc_if_version, if_version,
 			smu_version, smu_major, smu_minor, smu_debug);
-		pr_err("SMU driver if version not matched\n");
-		ret = -EINVAL;
+		pr_warn("SMU driver if version not matched\n");
 	}
 
 	return ret;