[PATCH] net: ethernet: mtk_wed: increase WED v2 WDMA RESV_BUFF to 0x80

[PATCH] net: ethernet: mtk_wed: increase WED v2 WDMA RESV_BUFF to 0x80

[Shiji Yang]

Change WDMA RESV_BUFF from 0x40 to 0x80 to avoid CDM TX FIFO overflow.
Without this patch mt7986 and mt7981 may have WDMA TX hang issue. This
patch was pulled from mtk-openwrt-feeds GPL open source project.

Link: https://github.com/mediatek/mtk-openwrt-feeds/commit/07c87502e854b68b48544d101b6fe17ec059b97b
Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
---
 drivers/net/ethernet/mediatek/mtk_wed.c      | 5 +++++
 drivers/net/ethernet/mediatek/mtk_wed_regs.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/mediatek/mtk_wed.c b/drivers/net/ethernet/mediatek/mtk_wed.c
index 10d9beaae..53d3b7e00 100644
--- a/drivers/net/ethernet/mediatek/mtk_wed.c
+++ b/drivers/net/ethernet/mediatek/mtk_wed.c
@@ -2071,6 +2071,11 @@ mtk_wed_dma_enable(struct mtk_wed_device *dev)
 		wdma_set(dev, MTK_WDMA_GLO_CFG, MTK_WDMA_GLO_CFG_TX_DMA_EN);
 	}
 
+	if (mtk_wed_is_v2(dev->hw))
+		wdma_m32(dev, MTK_WDMA_GLO_CFG,
+			 MTK_WDMA_GLO_CFG_RESV_BUFF,
+			 FIELD_PREP(MTK_WDMA_GLO_CFG_RESV_BUFF, 0x80));
+
 	wed_set(dev, MTK_WED_GLO_CFG,
 		MTK_WED_GLO_CFG_TX_DMA_EN |
 		MTK_WED_GLO_CFG_RX_DMA_EN);
diff --git a/drivers/net/ethernet/mediatek/mtk_wed_regs.h b/drivers/net/ethernet/mediatek/mtk_wed_regs.h
index c71190924..e5f83100d 100644
--- a/drivers/net/ethernet/mediatek/mtk_wed_regs.h
+++ b/drivers/net/ethernet/mediatek/mtk_wed_regs.h
@@ -433,6 +433,7 @@ struct mtk_wdma_desc {
 #define MTK_WDMA_GLO_CFG_TX_DMA_BUSY			BIT(1)
 #define MTK_WDMA_GLO_CFG_RX_DMA_EN			BIT(2)
 #define MTK_WDMA_GLO_CFG_RX_DMA_BUSY			BIT(3)
+#define MTK_WDMA_GLO_CFG_RESV_BUFF			GENMASK(23, 16)
 #define MTK_WDMA_GLO_CFG_RX_INFO3_PRERES		BIT(26)
 #define MTK_WDMA_GLO_CFG_RX_INFO2_PRERES		BIT(27)
 #define MTK_WDMA_GLO_CFG_RX_INFO1_PRERES		BIT(28)
-- 
2.53.0

Re: [PATCH] net: ethernet: mtk_wed: increase WED v2 WDMA RESV_BUFF to 0x80

[Simon Horman]

On Wed, Aug 19, 2026 at 09:07:07PM +0800, Shiji Yang wrote:
> Change WDMA RESV_BUFF from 0x40 to 0x80 to avoid CDM TX FIFO overflow.
> Without this patch mt7986 and mt7981 may have WDMA TX hang issue. This
> patch was pulled from mtk-openwrt-feeds GPL open source project.
> 
> Link: https://github.com/mediatek/mtk-openwrt-feeds/commit/07c87502e854b68b48544d101b6fe17ec059b97b
> Signed-off-by: Shiji Yang <yangshiji66@outlook.com>

As a bug fix for code present in the net tree, this should

1. Be targeted at the net tree

   Subject: [PATCH net] ...

2. Be CCed to stable

3. Have a fixes tag. Perhaps this one?

   Fixes: cf26df8833cc ("net: ethernet: mtk_eth_wed: add mtk_wed_configure_irq and mtk_wed_dma_{enable/disable}")

I'm unsure if the maintainers would like a repost because of this.
But at any rate, please keep it in mind for the future.

More information on the netdev development processes can be found here:
https://docs.kernel.org/process/maintainer-netdev.html

The above not withstanding, this looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>