2019-07-09 10:24:21

by Jian-Hong Pan

Subject: [PATCH v2 2/2] rtw88: pci: Use DMA sync instead of remapping in RX ISR

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 <[email protected]>
---
drivers/net/wireless/realtek/rtw88/pci.c | 35 ++++++++++++++++++++++--
1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c
index e9fe3ad896c8..28ca76f71dfe 100644
--- a/drivers/net/wireless/realtek/rtw88/pci.c
+++ b/drivers/net/wireless/realtek/rtw88/pci.c
@@ -206,6 +206,35 @@ static int rtw_pci_reset_rx_desc(struct rtw_dev *rtwdev, struct sk_buff *skb,
return 0;
}

+static int rtw_pci_sync_rx_desc_cpu(struct rtw_dev *rtwdev, dma_addr_t dma)
+{
+ struct device *dev = rtwdev->dev;
+ int buf_sz = RTK_PCI_RX_BUF_SIZE;
+
+ dma_sync_single_for_cpu(dev, dma, buf_sz, PCI_DMA_FROMDEVICE);
+
+ return 0;
+}
+
+static int 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, PCI_DMA_FROMDEVICE);
+
+ 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);
+
+ return 0;
+}
+
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 +811,7 @@ 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);
+ rtw_pci_sync_rx_desc_cpu(rtwdev, dma);
rx_desc = skb->data;
chip->ops->query_rx_desc(rtwdev, rx_desc, &pkt_stat, &rx_status);

@@ -818,7 +846,8 @@ 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

2019-07-09 16:17:41

by Christoph Hellwig

Subject: Re: [PATCH v2 2/2] rtw88: pci: Use DMA sync instead of remapping in RX ISR

On Tue, Jul 09, 2019 at 06:21:01PM +0800, Jian-Hong Pan wrote:
> 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 <[email protected]>
> ---
> drivers/net/wireless/realtek/rtw88/pci.c | 35 ++++++++++++++++++++++--
> 1 file changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c
> index e9fe3ad896c8..28ca76f71dfe 100644
> --- a/drivers/net/wireless/realtek/rtw88/pci.c
> +++ b/drivers/net/wireless/realtek/rtw88/pci.c
> @@ -206,6 +206,35 @@ static int rtw_pci_reset_rx_desc(struct rtw_dev *rtwdev, struct sk_buff *skb,
> return 0;
> }
>
> +static int rtw_pci_sync_rx_desc_cpu(struct rtw_dev *rtwdev, dma_addr_t dma)
> +{
> + struct device *dev = rtwdev->dev;
> + int buf_sz = RTK_PCI_RX_BUF_SIZE;
> +
> + dma_sync_single_for_cpu(dev, dma, buf_sz, PCI_DMA_FROMDEVICE);
> +
> + return 0;
> +}

No need to return a value from this helper. In fact I'm not even sure
you need the helper at all. Also please use the DMA_FROM_DEVICE
constant instead of the deprecated PCI variant.

> +static int 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, PCI_DMA_FROMDEVICE);
> +
> + 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);
> +
> + return 0;
> +}

Same comment on the PCI constant and the return value here.