netdev - [PATCH 1/2] net: fec: use dma_alloc

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Date:   Mon, 21 Nov 2022 10:56:30 +0100
From:   Christoph Hellwig <hch@....de>
To:     Greg Ungerer <gerg@...ux-m68k.org>,
        Joakim Zhang <qiangqing.zhang@....com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-m68k@...ts.linux-m68k.org, uclinux-dev@...inux.org,
        netdev@...r.kernel.org
Subject: [PATCH 1/2] net: fec: use dma_alloc_noncoherent for m532x

The m532x coldfire platforms can't properly implement dma_alloc_coherent
and currently just return noncoherent memory from it.  The fec driver
than works around this with a flush of all caches in the receive path.
Make this hack a little less bad by using the explicit
dma_alloc_noncoherent API and documenting the hacky cache flushes.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 drivers/net/ethernet/freescale/fec_main.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 28ef4d3c18789..5230698310b5e 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -1580,6 +1580,10 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
 	struct page *page;
 
 #ifdef CONFIG_M532x
+	/*
+	 * Hacky flush of all caches instead of using the DMA API for the TSO
+	 * headers.
+	 */
 	flush_cache_all();
 #endif
 	rxq = fep->rx_queue[queue_id];
@@ -3123,10 +3127,17 @@ static void fec_enet_free_queue(struct net_device *ndev)
 	for (i = 0; i < fep->num_tx_queues; i++)
 		if (fep->tx_queue[i] && fep->tx_queue[i]->tso_hdrs) {
 			txq = fep->tx_queue[i];
+#ifdef CONFIG_M532x
 			dma_free_coherent(&fep->pdev->dev,
 					  txq->bd.ring_size * TSO_HEADER_SIZE,
 					  txq->tso_hdrs,
 					  txq->tso_hdrs_dma);
+#else
+			dma_free_noncoherent(&fep->pdev->dev,
+					  txq->bd.ring_size * TSO_HEADER_SIZE,
+					  txq->tso_hdrs, txq->tso_hdrs_dma,
+					  DMA_BIDIRECTIONAL);
+#endif
 		}
 
 	for (i = 0; i < fep->num_rx_queues; i++)
@@ -3157,10 +3168,18 @@ static int fec_enet_alloc_queue(struct net_device *ndev)
 		txq->tx_wake_threshold =
 			(txq->bd.ring_size - txq->tx_stop_threshold) / 2;
 
+#ifdef CONFIG_M532x
 		txq->tso_hdrs = dma_alloc_coherent(&fep->pdev->dev,
 					txq->bd.ring_size * TSO_HEADER_SIZE,
 					&txq->tso_hdrs_dma,
 					GFP_KERNEL);
+#else
+		/* m68knommu manually flushes all caches in fec_enet_rx_queue */
+		txq->tso_hdrs = dma_alloc_noncoherent(&fep->pdev->dev,
+					txq->bd.ring_size * TSO_HEADER_SIZE,
+					&txq->tso_hdrs_dma, DMA_BIDIRECTIONAL,
+					GFP_KERNEL);
+#endif
 		if (!txq->tso_hdrs) {
 			ret = -ENOMEM;
 			goto alloc_failed;
-- 
2.30.2