[PATCH net-next v2 2/5] lan743x: sync only the received area of an rx ring buffer
From: Sven Van Asbroeck <hidden>
Date: 2021-02-11 17:18:25
Also in:
lkml
Subsystem:
microchip lan743x ethernet driver, networking drivers, the rest · Maintainers:
Bryan Whitehead, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Sven Van Asbroeck <redacted> On cpu architectures w/o dma cache snooping, dma_unmap() is a is a very expensive operation, because its resulting sync needs to invalidate cpu caches. Increase efficiency/performance by syncing only those sections of the lan743x's rx ring buffers that are actually in use. Signed-off-by: Sven Van Asbroeck <redacted> --- To: Bryan Whitehead <bryan.whitehead@microchip.com> To: UNGLinuxDriver@microchip.com To: "David S. Miller" <davem@davemloft.net> To: Jakub Kicinski <kuba@kernel.org> Cc: Andrew Lunn <andrew@lunn.ch> Cc: Alexey Denisov <redacted> Cc: Sergej Bauer <redacted> Cc: Tim Harvey <tharvey@gateworks.com> Cc: Anders Rønningen <redacted> Cc: Hillf Danton <redacted> Cc: Christoph Hellwig <hch@lst.de> Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com> Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org drivers/net/ethernet/microchip/lan743x_main.c | 32 +++++++++++++------ 1 file changed, 23 insertions(+), 9 deletions(-)
diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index 0c48bb559719..36cc67c72851 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c@@ -1968,35 +1968,49 @@ static int lan743x_rx_init_ring_element(struct lan743x_rx *rx, int index) struct net_device *netdev = rx->adapter->netdev; struct device *dev = &rx->adapter->pdev->dev; struct lan743x_rx_buffer_info *buffer_info; + unsigned int buffer_length, packet_length; struct lan743x_rx_descriptor *descriptor; struct sk_buff *skb; dma_addr_t dma_ptr; - int length; - length = netdev->mtu + ETH_HLEN + 4 + RX_HEAD_PADDING; + buffer_length = netdev->mtu + ETH_HLEN + 4 + RX_HEAD_PADDING; descriptor = &rx->ring_cpu_ptr[index]; buffer_info = &rx->buffer_info[index]; - skb = __netdev_alloc_skb(netdev, length, GFP_ATOMIC | GFP_DMA); + skb = __netdev_alloc_skb(netdev, buffer_length, GFP_ATOMIC | GFP_DMA); if (!skb) return -ENOMEM; - dma_ptr = dma_map_single(dev, skb->data, length, DMA_FROM_DEVICE); + dma_ptr = dma_map_single(dev, skb->data, buffer_length, DMA_FROM_DEVICE); if (dma_mapping_error(dev, dma_ptr)) { dev_kfree_skb_any(skb); return -ENOMEM; } - if (buffer_info->dma_ptr) - dma_unmap_single(dev, buffer_info->dma_ptr, - buffer_info->buffer_length, DMA_FROM_DEVICE); + if (buffer_info->dma_ptr) { + /* unmap from dma */ + packet_length = RX_DESC_DATA0_FRAME_LENGTH_GET_ + (le32_to_cpu(descriptor->data0)); + if (packet_length == 0 || + packet_length > buffer_info->buffer_length) + /* buffer is part of multi-buffer packet: fully used */ + packet_length = buffer_info->buffer_length; + /* sync used part of buffer only */ + dma_sync_single_for_cpu(dev, buffer_info->dma_ptr, + packet_length, + DMA_FROM_DEVICE); + dma_unmap_single_attrs(dev, buffer_info->dma_ptr, + buffer_info->buffer_length, + DMA_FROM_DEVICE, + DMA_ATTR_SKIP_CPU_SYNC); + } buffer_info->skb = skb; buffer_info->dma_ptr = dma_ptr; - buffer_info->buffer_length = length; + buffer_info->buffer_length = buffer_length; descriptor->data1 = cpu_to_le32(DMA_ADDR_LOW32(buffer_info->dma_ptr)); descriptor->data2 = cpu_to_le32(DMA_ADDR_HIGH32(buffer_info->dma_ptr)); descriptor->data3 = 0; descriptor->data0 = cpu_to_le32((RX_DESC_DATA0_OWN_ | - (length & RX_DESC_DATA0_BUF_LENGTH_MASK_))); + (buffer_length & RX_DESC_DATA0_BUF_LENGTH_MASK_))); lan743x_rx_update_tail(rx, index); return 0;
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2.17.1