[PATCH v3 2/2] rtw88: pci: Use DMA sync instead of remapping in RX ISR

[Jian-Hong Pan]

Since each skb in RX ring is reused instead of new allocation, we can
treat the DMA in a more efficient way by DMA synchronization.

Signed-off-by: Jian-Hong Pan <jian-h...@endlessm.com>
Cc: <sta...@vger.kernel.org>
---
v2:
 - New patch by following [PATCH v3 1/2] rtw88: pci: Rearrange the
   memory usage for skb in RX ISR.

v3:
 - Remove rtw_pci_sync_rx_desc_cpu and call dma_sync_single_for_cpu in
   rtw_pci_rx_isr directly.
 - Remove the return value of rtw_pci_sync_rx_desc_device.
 - Use DMA_FROM_DEVICE instead of PCI_DMA_FROMDEVICE.

 drivers/net/wireless/realtek/rtw88/pci.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw88/pci.c 
b/drivers/net/wireless/realtek/rtw88/pci.c
index e9fe3ad896c8..485d30c06935 100644
--- a/drivers/net/wireless/realtek/rtw88/pci.c
+++ b/drivers/net/wireless/realtek/rtw88/pci.c
@@ -206,6 +206,23 @@ static int rtw_pci_reset_rx_desc(struct rtw_dev *rtwdev, 
struct sk_buff *skb,
        return 0;
 }
 
+static void rtw_pci_sync_rx_desc_device(struct rtw_dev *rtwdev, dma_addr_t dma,
+                                       struct rtw_pci_rx_ring *rx_ring,
+                                       u32 idx, u32 desc_sz)
+{
+       struct device *dev = rtwdev->dev;
+       struct rtw_pci_rx_buffer_desc *buf_desc;
+       int buf_sz = RTK_PCI_RX_BUF_SIZE;
+
+       dma_sync_single_for_device(dev, dma, buf_sz, DMA_FROM_DEVICE);
+
+       buf_desc = (struct rtw_pci_rx_buffer_desc *)(rx_ring->r.head +
+                                                    idx * desc_sz);
+       memset(buf_desc, 0, sizeof(*buf_desc));
+       buf_desc->buf_size = cpu_to_le16(RTK_PCI_RX_BUF_SIZE);
+       buf_desc->dma = cpu_to_le32(dma);
+}
+
 static int rtw_pci_init_rx_ring(struct rtw_dev *rtwdev,
                                struct rtw_pci_rx_ring *rx_ring,
                                u8 desc_size, u32 len)
@@ -782,8 +799,8 @@ static void rtw_pci_rx_isr(struct rtw_dev *rtwdev, struct 
rtw_pci *rtwpci,
                rtw_pci_dma_check(rtwdev, ring, cur_rp);
                skb = ring->buf[cur_rp];
                dma = *((dma_addr_t *)skb->cb);
-               pci_unmap_single(rtwpci->pdev, dma, RTK_PCI_RX_BUF_SIZE,
-                                PCI_DMA_FROMDEVICE);
+               dma_sync_single_for_cpu(rtwdev->dev, dma, RTK_PCI_RX_BUF_SIZE,
+                                       DMA_FROM_DEVICE);
                rx_desc = skb->data;
                chip->ops->query_rx_desc(rtwdev, rx_desc, &pkt_stat, 
&rx_status);
 
@@ -818,7 +835,8 @@ static void rtw_pci_rx_isr(struct rtw_dev *rtwdev, struct 
rtw_pci *rtwpci,
 
 next_rp:
                /* new skb delivered to mac80211, re-enable original skb DMA */
-               rtw_pci_reset_rx_desc(rtwdev, skb, ring, cur_rp, buf_desc_sz);
+               rtw_pci_sync_rx_desc_device(rtwdev, dma, ring, cur_rp,
+                                           buf_desc_sz);
 
                /* host read next element in ring */
                if (++cur_rp >= ring->r.len)
-- 
2.22.0