diff --git a/package/kernel/mac80211/patches/349-v4.21-0001-brcmutil-print-invalid-chanspec-when-WARN-ing.patch b/package/kernel/mac80211/patches/349-v4.21-0001-brcmutil-print-invalid-chanspec-when-WARN-ing.patch
new file mode 100644
index 00000000000..566336cbc32
--- /dev/null
+++ b/package/kernel/mac80211/patches/349-v4.21-0001-brcmutil-print-invalid-chanspec-when-WARN-ing.patch
@@ -0,0 +1,83 @@
+From ae5848cb4511bbbfe0306fcdbe5d9a95cd9546a9 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
+Date: Fri, 26 Oct 2018 13:22:32 +0200
+Subject: [PATCH] brcmutil: print invalid chanspec when WARN-ing
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+On one of my devices I got WARNINGs when brcmfmac tried to decode
+chanspec. I couldn't tell if it was some unsupported format or just a
+malformed value passed by a firmware.
+
+Print chanspec value so it's possible to debug a possible problem.
+
+Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
+Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
+---
+ drivers/net/wireless/broadcom/brcm80211/brcmutil/d11.c | 14 +++++++-------
+ 1 file changed, 7 insertions(+), 7 deletions(-)
+
+--- a/drivers/net/wireless/broadcom/brcm80211/brcmutil/d11.c
++++ b/drivers/net/wireless/broadcom/brcm80211/brcmutil/d11.c
+@@ -128,7 +128,7 @@ static void brcmu_d11n_decchspec(struct
+ 		}
+ 		break;
+ 	default:
+-		WARN_ON_ONCE(1);
++		WARN_ONCE(1, "Invalid chanspec 0x%04x\n", ch->chspec);
+ 		break;
+ 	}
+ 
+@@ -140,7 +140,7 @@ static void brcmu_d11n_decchspec(struct
+ 		ch->band = BRCMU_CHAN_BAND_2G;
+ 		break;
+ 	default:
+-		WARN_ON_ONCE(1);
++		WARN_ONCE(1, "Invalid chanspec 0x%04x\n", ch->chspec);
+ 		break;
+ 	}
+ }
+@@ -167,7 +167,7 @@ static void brcmu_d11ac_decchspec(struct
+ 			ch->sb = BRCMU_CHAN_SB_U;
+ 			ch->control_ch_num += CH_10MHZ_APART;
+ 		} else {
+-			WARN_ON_ONCE(1);
++			WARN_ONCE(1, "Invalid chanspec 0x%04x\n", ch->chspec);
+ 		}
+ 		break;
+ 	case BRCMU_CHSPEC_D11AC_BW_80:
+@@ -188,7 +188,7 @@ static void brcmu_d11ac_decchspec(struct
+ 			ch->control_ch_num += CH_30MHZ_APART;
+ 			break;
+ 		default:
+-			WARN_ON_ONCE(1);
++			WARN_ONCE(1, "Invalid chanspec 0x%04x\n", ch->chspec);
+ 			break;
+ 		}
+ 		break;
+@@ -222,13 +222,13 @@ static void brcmu_d11ac_decchspec(struct
+ 			ch->control_ch_num += CH_70MHZ_APART;
+ 			break;
+ 		default:
+-			WARN_ON_ONCE(1);
++			WARN_ONCE(1, "Invalid chanspec 0x%04x\n", ch->chspec);
+ 			break;
+ 		}
+ 		break;
+ 	case BRCMU_CHSPEC_D11AC_BW_8080:
+ 	default:
+-		WARN_ON_ONCE(1);
++		WARN_ONCE(1, "Invalid chanspec 0x%04x\n", ch->chspec);
+ 		break;
+ 	}
+ 
+@@ -240,7 +240,7 @@ static void brcmu_d11ac_decchspec(struct
+ 		ch->band = BRCMU_CHAN_BAND_2G;
+ 		break;
+ 	default:
+-		WARN_ON_ONCE(1);
++		WARN_ONCE(1, "Invalid chanspec 0x%04x\n", ch->chspec);
+ 		break;
+ 	}
+ }