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Subject[PATCH net-next 11/14] net: ethernet: mtk_eth_soc: only read the full RX descriptor if DMA is done
Date
From: Felix Fietkau <nbd@nbd.name>

Uncached memory access is expensive, and there is no need to access all
descriptor words if we can't process them anyway

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>
---
drivers/net/ethernet/mediatek/mtk_eth_soc.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index 01ad10c76d53..5a531bb83348 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -775,13 +775,18 @@ static inline int mtk_max_buf_size(int frag_size)
return buf_size;
}

-static inline void mtk_rx_get_desc(struct mtk_rx_dma *rxd,
+static inline bool mtk_rx_get_desc(struct mtk_rx_dma *rxd,
struct mtk_rx_dma *dma_rxd)
{
- rxd->rxd1 = READ_ONCE(dma_rxd->rxd1);
rxd->rxd2 = READ_ONCE(dma_rxd->rxd2);
+ if (!(rxd->rxd2 & RX_DMA_DONE))
+ return false;
+
+ rxd->rxd1 = READ_ONCE(dma_rxd->rxd1);
rxd->rxd3 = READ_ONCE(dma_rxd->rxd3);
rxd->rxd4 = READ_ONCE(dma_rxd->rxd4);
+
+ return true;
}

/* the qdma core needs scratch memory to be setup */
@@ -1253,8 +1258,7 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget,
rxd = &ring->dma[idx];
data = ring->data[idx];

- mtk_rx_get_desc(&trxd, rxd);
- if (!(trxd.rxd2 & RX_DMA_DONE))
+ if (!mtk_rx_get_desc(&trxd, rxd))
break;

/* find out which mac the packet come from. values start at 1 */
--
2.31.1
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