netdev - [PATCH v3 net-next 4/8] net: mvneta: sync dma buffers before refilling hw queues

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Date:   Mon, 14 Oct 2019 12:49:51 +0200
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     netdev@...r.kernel.org
Cc:     lorenzo.bianconi@...hat.com, davem@...emloft.net,
        thomas.petazzoni@...tlin.com, brouer@...hat.com,
        ilias.apalodimas@...aro.org, matteo.croce@...hat.com,
        mw@...ihalf.com
Subject: [PATCH v3 net-next 4/8] net: mvneta: sync dma buffers before refilling hw queues

mvneta driver can run on not cache coherent devices so it is
necessary to sync DMA buffers before sending them to the device
in order to avoid memory corruptions. Running perf analysis we can
see a performance cost associated with this DMA-sync (anyway it is
already there in the original driver code). In follow up patches we
will add more logic to reduce DMA-sync as much as possible.

Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
 drivers/net/ethernet/marvell/mvneta.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 77d4e8a48dd9..1722dffe265d 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -1821,6 +1821,7 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
 			    struct mvneta_rx_queue *rxq,
 			    gfp_t gfp_mask)
 {
+	enum dma_data_direction dma_dir;
 	dma_addr_t phys_addr;
 	struct page *page;
 
@@ -1830,6 +1831,9 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
 		return -ENOMEM;
 
 	phys_addr = page_pool_get_dma_addr(page) + pp->rx_offset_correction;
+	dma_dir = page_pool_get_dma_dir(rxq->page_pool);
+	dma_sync_single_for_device(pp->dev->dev.parent, phys_addr,
+				   MVNETA_MAX_RX_BUF_SIZE, dma_dir);
 	mvneta_rx_desc_fill(rx_desc, phys_addr, page, rxq);
 
 	return 0;
-- 
2.21.0