netdev - [PATCH 5/6] net: fec: use dma_alloc

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Message-Id: <20231009074121.219686-6-hch@lst.de>
Date: Mon,  9 Oct 2023 09:41:20 +0200
From: Christoph Hellwig <hch@....de>
To: iommu@...ts.linux.dev
Cc: Robin Murphy <robin.murphy@....com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Wei Fang <wei.fang@....com>,
	Shenwei Wang <shenwei.wang@....com>,
	Clark Wang <xiaoning.wang@....com>,
	NXP Linux Team <linux-imx@....com>,
	linux-m68k@...ts.linux-m68k.org,
	netdev@...r.kernel.org,
	Jim Quinlan <james.quinlan@...adcom.com>
Subject: [PATCH 5/6] net: fec: use dma_alloc_noncoherent for m532x

The coldfire platforms can't properly implement dma_alloc_coherent and
currently just return noncoherent memory from dma_alloc_coherent.

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 so
that the DMA API level hack can be removed.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 drivers/net/ethernet/freescale/fec_main.c | 84 ++++++++++++++++++++---
 1 file changed, 75 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 77c8e9cfb44562..aa032ea0ebf0c2 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -406,6 +406,70 @@ static void fec_dump(struct net_device *ndev)
 	} while (bdp != txq->bd.base);
 }
 
+/*
+ * Coldfire does not support DMA coherent allocations, and has historically used
+ * a band-aid with a manual flush in fec_enet_rx_queue.
+ */
+#ifdef CONFIG_COLDFIRE
+static void *fec_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
+		gfp_t gfp)
+{
+	return dma_alloc_noncoherent(dev, size, handle, DMA_BIDIRECTIONAL, gfp);
+}
+
+static void fec_dma_free(struct device *dev, size_t size, void *cpu_addr,
+		dma_addr_t handle)
+{
+	dma_free_noncoherent(dev, size, cpu_addr, handle, DMA_BIDIRECTIONAL);
+}
+#else /* CONFIG_COLDFIRE */
+static void *fec_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
+		gfp_t gfp)
+{
+	return dma_alloc_coherent(dev, size, handle, gfp);
+}
+
+static void fec_dma_free(struct device *dev, size_t size, void *cpu_addr,
+		dma_addr_t handle)
+{
+	dma_free_coherent(dev, size, cpu_addr, handle);
+}
+#endif /* !CONFIG_COLDFIRE */
+
+struct fec_dma_devres {
+	size_t		size;
+	void		*vaddr;
+	dma_addr_t	dma_handle;
+};
+
+static void fec_dmam_release(struct device *dev, void *res)
+{
+	struct fec_dma_devres *this = res;
+
+	fec_dma_free(dev, this->size, this->vaddr, this->dma_handle);
+}
+
+static void *fec_dmam_alloc(struct device *dev, size_t size, dma_addr_t *handle,
+		gfp_t gfp)
+{
+	struct fec_dma_devres *dr;
+	void *vaddr;
+
+	dr = devres_alloc(fec_dmam_release, sizeof(*dr), gfp);
+	if (!dr)
+		return NULL;
+	vaddr = fec_dma_alloc(dev, size, handle, gfp);
+	if (!vaddr) {
+		devres_free(dr);
+		return NULL;
+	}
+	dr->vaddr = vaddr;
+	dr->dma_handle = *handle;
+	dr->size = size;
+	devres_add(dev, dr);
+	return vaddr;
+}
+
 static inline bool is_ipv4_pkt(struct sk_buff *skb)
 {
 	return skb->protocol == htons(ETH_P_IP) && ip_hdr(skb)->version == 4;
@@ -1661,6 +1725,10 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
 #endif
 
 #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];
@@ -3288,10 +3356,9 @@ 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];
-			dma_free_coherent(&fep->pdev->dev,
-					  txq->bd.ring_size * TSO_HEADER_SIZE,
-					  txq->tso_hdrs,
-					  txq->tso_hdrs_dma);
+			fec_dma_free(&fep->pdev->dev,
+				     txq->bd.ring_size * TSO_HEADER_SIZE,
+				     txq->tso_hdrs, txq->tso_hdrs_dma);
 		}
 
 	for (i = 0; i < fep->num_rx_queues; i++)
@@ -3321,10 +3388,9 @@ static int fec_enet_alloc_queue(struct net_device *ndev)
 		txq->tx_stop_threshold = FEC_MAX_SKB_DESCS;
 		txq->tx_wake_threshold = FEC_MAX_SKB_DESCS + 2 * MAX_SKB_FRAGS;
 
-		txq->tso_hdrs = dma_alloc_coherent(&fep->pdev->dev,
+		txq->tso_hdrs = fec_dma_alloc(&fep->pdev->dev,
 					txq->bd.ring_size * TSO_HEADER_SIZE,
-					&txq->tso_hdrs_dma,
-					GFP_KERNEL);
+					&txq->tso_hdrs_dma, GFP_KERNEL);
 		if (!txq->tso_hdrs) {
 			ret = -ENOMEM;
 			goto alloc_failed;
@@ -4043,8 +4109,8 @@ static int fec_enet_init(struct net_device *ndev)
 	bd_size = (fep->total_tx_ring_size + fep->total_rx_ring_size) * dsize;
 
 	/* Allocate memory for buffer descriptors. */
-	cbd_base = dmam_alloc_coherent(&fep->pdev->dev, bd_size, &bd_dma,
-				       GFP_KERNEL);
+	cbd_base = fec_dmam_alloc(&fep->pdev->dev, bd_size, &bd_dma,
+				  GFP_KERNEL);
 	if (!cbd_base) {
 		ret = -ENOMEM;
 		goto free_queue_mem;
-- 
2.39.2