[PATCH net] net: ethernet: mtk_eth_soc: fix SER panic with 4GB+ RAM

[Daniel Golle]

On Sat, Apr 26, 2025 at 02:25:23AM +0100, Daniel Golle wrote:
> From: Chad Monroe <chad at monroe.io>
> 
> If the mtk_poll_rx() function detects the MTK_RESETTING flag, it will
> jump to release_desc and refill the high word of the SDP on the 4GB RFB.
> Subsequently, mtk_rx_clean will process an incorrect SDP, leading to a
> panic.
> 
> Add patch from Mediatek SDK to resolve this.
> 
> Fixes: 2d75891ebc09 ("net: ethernet: mtk_eth_soc: support 36-bit DMA addressing on MT7988")
> Link: https://git01.mediatek.com/plugins/gitiles/openwrt/feeds/mtk-openwrt-feeds/+/11857ce2f90bf065b5e53211d182622d999a4542

The above link has to be replaced by
Link: https://git01.mediatek.com/plugins/gitiles/openwrt/feeds/mtk-openwrt-feeds/+/71f47ea785699c6aa3b922d66c2bdc1a43da25b1

> Signed-off-by: Chad Monroe <chad at monroe.io>
> ---
>  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index 47807b202310..7bac5ccfb79c 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -2252,14 +2252,17 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget,
>  		ring->data[idx] = new_data;
>  		rxd->rxd1 = (unsigned int)dma_addr;
>  release_desc:
> +		if (MTK_HAS_CAPS(eth->soc->caps, MTK_36BIT_DMA)) {
> +			if (unlikely(dma_addr == DMA_MAPPING_ERROR))
> +				addr64 = FIELD_GET(RX_DMA_ADDR64_MASK, rxd->rxd2);
> +			else
> +				addr64 = RX_DMA_PREP_ADDR64(dma_addr);
> +		}
> +
>  		if (MTK_HAS_CAPS(eth->soc->caps, MTK_SOC_MT7628))
>  			rxd->rxd2 = RX_DMA_LSO;
>  		else
> -			rxd->rxd2 = RX_DMA_PREP_PLEN0(ring->buf_size);
> -
> -		if (MTK_HAS_CAPS(eth->soc->caps, MTK_36BIT_DMA) &&
> -		    likely(dma_addr != DMA_MAPPING_ERROR))
> -			rxd->rxd2 |= RX_DMA_PREP_ADDR64(dma_addr);
> +			rxd->rxd2 = RX_DMA_PREP_PLEN0(ring->buf_size) | addr64;
>  
>  		ring->calc_idx = idx;
>  		done++;
> -- 
> 2.49.0
> 
>