netdev - [PATCH net v2] net: mtk: wed: add dma mask limitation and GFP

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Message-Id: <20251009-wed-4g-ram-limitation-v2-1-c0ca75b26a29@kernel.org>
Date: Thu, 09 Oct 2025 08:29:34 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Felix Fietkau <nbd@....name>, Sean Wang <sean.wang@...iatek.com>, 
 Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Matthias Brugger <matthias.bgg@...il.com>, 
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
 Lorenzo Bianconi <lorenzo@...nel.org>, 
 Sujuan Chen <sujuan.chen@...iatek.com>
Cc: netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 linux-mediatek@...ts.infradead.org, Rex Lu <rex.lu@...iatek.com>, 
 Daniel Pawlik <pawlik.dan@...il.com>, Matteo Croce <teknoraver@...a.com>
Subject: [PATCH net v2] net: mtk: wed: add dma mask limitation and
 GFP_DMA32 for device with more than 4GB DRAM

From: Rex Lu <rex.lu@...iatek.com>

Limit tx/rx buffer address to 32-bit address space for board with more
than 4GB DRAM.

Fixes: 804775dfc2885 ("net: ethernet: mtk_eth_soc: add support for Wireless Ethernet Dispatch (WED)")
Fixes: 6757d345dd7db ("net: ethernet: mtk_wed: introduce hw_rro support for MT7988")
Tested-by: Daniel Pawlik <pawlik.dan@...il.com>
Tested-by: Matteo Croce <teknoraver@...a.com>
Signed-off-by: Rex Lu <rex.lu@...iatek.com>
Co-developed-by: Lorenzo Bianconi <lorenzo@...nel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
Changes in v2:
- Add missing Fixes tags
- Avoid possible deadlock if dma_set_mask_and_coherent fails
- Link to v1: https://lore.kernel.org/r/20251008-wed-4g-ram-limitation-v1-1-16fe55e1d042@kernel.org
---
 drivers/net/ethernet/mediatek/mtk_wed.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_wed.c b/drivers/net/ethernet/mediatek/mtk_wed.c
index 3dbb113b792cf00fb4f89ab20f7e7fa72ecac260..1ed1f88dd7f8bc69bf4cb2803b907c8d7776ae20 100644
--- a/drivers/net/ethernet/mediatek/mtk_wed.c
+++ b/drivers/net/ethernet/mediatek/mtk_wed.c
@@ -677,7 +677,7 @@ mtk_wed_tx_buffer_alloc(struct mtk_wed_device *dev)
 		void *buf;
 		int s;

-		page = __dev_alloc_page(GFP_KERNEL);
+		page = __dev_alloc_page(GFP_KERNEL | GFP_DMA32);
 		if (!page)
 			return -ENOMEM;

@@ -800,7 +800,7 @@ mtk_wed_hwrro_buffer_alloc(struct mtk_wed_device *dev)
 		struct page *page;
 		int s;

-		page = __dev_alloc_page(GFP_KERNEL);
+		page = __dev_alloc_page(GFP_KERNEL | GFP_DMA32);
 		if (!page)
 			return -ENOMEM;

@@ -2426,6 +2426,10 @@ mtk_wed_attach(struct mtk_wed_device *dev)
 	dev->version = hw->version;
 	dev->hw->pcie_base = mtk_wed_get_pcie_base(dev);

+	ret = dma_set_mask_and_coherent(hw->dev, DMA_BIT_MASK(32));
+	if (ret)
+		goto out;
+
 	if (hw->eth->dma_dev == hw->eth->dev &&
 	    of_dma_is_coherent(hw->eth->dev->of_node))
 		mtk_eth_set_dma_device(hw->eth, hw->dev);

---
base-commit: 07fdad3a93756b872da7b53647715c48d0f4a2d0
change-id: 20250930-wed-4g-ram-limitation-6490e7ed9d39

Best regards,
-- 
Lorenzo Bianconi <lorenzo@...nel.org>