From nobody Mon Jun 15 07:35:32 2026 Received: from pidgin.makrotopia.org (pidgin.makrotopia.org [185.142.180.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 568FD3890F3; Wed, 8 Apr 2026 23:34:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.142.180.65 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775691260; cv=none; b=FkJvhu3pZ9dhNcJypEo4O3TO8akwzQvNHQanEr/lZbNBaNk1avsqqno7crBpg+TWqPWNe5WCIjJtOM2OouwRffqKsbMAc5QUVvaNY9tLP3I7FUvDh1MTUt+1iHg2IlN27Yoe+HifUo2KdMKtt7hg+odBqD0pCFqikrV1nz8SlD4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775691260; c=relaxed/simple; bh=owcjYvHdhsk/xKPWAlGi5smlRrt8tgbOLgudLUwyWL4=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=mDhpjlENE1AyBoKCIIY8c2HnDK1OgrscwKNqgKVd+ArQIM6wgK6Hg9xwR+Gw8xGvYitvEaCp/7sNEeBy1sVtqswkkjaahZoSFn2J0eMyOdnEQGwfQ/rbeq5DkOkIdElec6jN3QR+GJ4gVzj2sgFhHlFmokzkfmNu0lxpnXH4Bek= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=makrotopia.org; spf=pass smtp.mailfrom=makrotopia.org; arc=none smtp.client-ip=185.142.180.65 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=makrotopia.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=makrotopia.org Received: from local by pidgin.makrotopia.org with esmtpsa (TLS1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.99) (envelope-from ) id 1wAcPF-000000004lk-2YmF; Wed, 08 Apr 2026 23:33:57 +0000 Date: Thu, 9 Apr 2026 00:33:47 +0100 From: Daniel Golle To: Felix Fietkau , Lorenzo Bianconi , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Matthias Brugger , AngeloGioacchino Del Regno , Pablo Neira Ayuso , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org Cc: Chad Monroe , Elad Yifee , =?iso-8859-1?Q?Jo=E3o?= Duarte , John Crispin Subject: [PATCH net] net: ethernet: mtk_eth_soc: initialize PPE per-tag-layer MTU registers Message-ID: <164435c1de5b4ccfd773ee623ad1bc65b5366250.1775690659.git.daniel@makrotopia.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The PPE enforces output frame size limits via per-tag-layer VLAN_MTU registers that the driver never initializes. The hardware defaults do not account for PPPoE overhead, causing the PPE to punt encapsulated frames back to the CPU instead of forwarding them. Initialize the registers at PPE start and on MTU changes using the maximum GMAC MTU. This is a conservative approximation -- the actual per-PPE requirement depends on egress path, but using the global maximum ensures the limits are never too small. Fixes: ba37b7caf1ed2 ("net: ethernet: mtk_eth_soc: add support for initiali= zing the PPE") Signed-off-by: Daniel Golle --- drivers/net/ethernet/mediatek/mtk_eth_soc.c | 22 ++++++++++++++- drivers/net/ethernet/mediatek/mtk_ppe.c | 30 +++++++++++++++++++++ drivers/net/ethernet/mediatek/mtk_ppe.h | 1 + 3 files changed, 52 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethe= rnet/mediatek/mtk_eth_soc.c index 1767463475de4..06880fa86f0ea 100644 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c @@ -3922,12 +3922,23 @@ static int mtk_device_event(struct notifier_block *= n, unsigned long event, void return NOTIFY_DONE; } =20 +static int mtk_max_gmac_mtu(struct mtk_eth *eth) +{ + int i, max_mtu =3D ETH_DATA_LEN; + + for (i =3D 0; i < ARRAY_SIZE(eth->netdev); i++) + if (eth->netdev[i] && eth->netdev[i]->mtu > max_mtu) + max_mtu =3D eth->netdev[i]->mtu; + + return max_mtu; +} + static int mtk_open(struct net_device *dev) { struct mtk_mac *mac =3D netdev_priv(dev); struct mtk_eth *eth =3D mac->hw; struct mtk_mac *target_mac; - int i, err, ppe_num; + int i, err, ppe_num, mtu; =20 ppe_num =3D eth->soc->ppe_num; =20 @@ -3974,6 +3985,10 @@ static int mtk_open(struct net_device *dev) mtk_gdm_config(eth, target_mac->id, gdm_config); } =20 + mtu =3D mtk_max_gmac_mtu(eth); + for (i =3D 0; i < ARRAY_SIZE(eth->ppe); i++) + mtk_ppe_update_mtu(eth->ppe[i], mtu); + napi_enable(ð->tx_napi); napi_enable(ð->rx_napi[0].napi); mtk_tx_irq_enable(eth, MTK_TX_DONE_INT); @@ -4788,6 +4803,7 @@ static int mtk_change_mtu(struct net_device *dev, int= new_mtu) int length =3D new_mtu + MTK_RX_ETH_HLEN; struct mtk_mac *mac =3D netdev_priv(dev); struct mtk_eth *eth =3D mac->hw; + int max_mtu, i; =20 if (rcu_access_pointer(eth->prog) && length > MTK_PP_MAX_BUF_SIZE) { @@ -4798,6 +4814,10 @@ static int mtk_change_mtu(struct net_device *dev, in= t new_mtu) mtk_set_mcr_max_rx(mac, length); WRITE_ONCE(dev->mtu, new_mtu); =20 + max_mtu =3D mtk_max_gmac_mtu(eth); + for (i =3D 0; i < ARRAY_SIZE(eth->ppe); i++) + mtk_ppe_update_mtu(eth->ppe[i], max_mtu); + return 0; } =20 diff --git a/drivers/net/ethernet/mediatek/mtk_ppe.c b/drivers/net/ethernet= /mediatek/mtk_ppe.c index 79c11e179d894..9e829a2e4354e 100644 --- a/drivers/net/ethernet/mediatek/mtk_ppe.c +++ b/drivers/net/ethernet/mediatek/mtk_ppe.c @@ -973,6 +973,36 @@ static void mtk_ppe_init_foe_table(struct mtk_ppe *ppe) } } =20 +void mtk_ppe_update_mtu(struct mtk_ppe *ppe, int mtu) +{ + int base; + u32 val; + + if (!ppe) + return; + + /* The PPE checks output frame size against per-tag-layer MTU limits, + * treating PPPoE and DSA tags just like 802.1Q VLAN tags. The Linux + * device MTU already accounts for PPPoE (PPPOE_SES_HLEN) and DSA tag + * overhead, but 802.1Q VLAN tags are handled transparently without + * being reflected by the lower device MTU being increased by 4. + * Use the maximum MTU across all GMAC interfaces so that PPE output + * frame limits are sufficiently high regardless of which port a flow + * egresses through. + */ + base =3D ETH_HLEN + mtu; + + val =3D FIELD_PREP(MTK_PPE_VLAN_MTU0_NONE, base) | + FIELD_PREP(MTK_PPE_VLAN_MTU0_1TAG, base + VLAN_HLEN); + ppe_w32(ppe, MTK_PPE_VLAN_MTU0, val); + + val =3D FIELD_PREP(MTK_PPE_VLAN_MTU1_2TAG, + base + 2 * VLAN_HLEN) | + FIELD_PREP(MTK_PPE_VLAN_MTU1_3TAG, + base + 3 * VLAN_HLEN); + ppe_w32(ppe, MTK_PPE_VLAN_MTU1, val); +} + void mtk_ppe_start(struct mtk_ppe *ppe) { u32 val; diff --git a/drivers/net/ethernet/mediatek/mtk_ppe.h b/drivers/net/ethernet= /mediatek/mtk_ppe.h index 223f709e2704f..ba85e39a155bf 100644 --- a/drivers/net/ethernet/mediatek/mtk_ppe.h +++ b/drivers/net/ethernet/mediatek/mtk_ppe.h @@ -346,6 +346,7 @@ struct mtk_ppe { struct mtk_ppe *mtk_ppe_init(struct mtk_eth *eth, void __iomem *base, int = index); =20 void mtk_ppe_deinit(struct mtk_eth *eth); +void mtk_ppe_update_mtu(struct mtk_ppe *ppe, int mtu); void mtk_ppe_start(struct mtk_ppe *ppe); int mtk_ppe_stop(struct mtk_ppe *ppe); int mtk_ppe_prepare_reset(struct mtk_ppe *ppe); --=20 2.53.0