netdev - Re: [PATCH v4 2/2] rtw88: pci: Use DMA sync instead of remapping in RX ISR

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Date:   Thu, 11 Jul 2019 13:30:25 +0800
From:   Jian-Hong Pan <jian-hong@...lessm.com>
To:     Yan-Hsuan Chuang <yhchuang@...ltek.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S . Miller" <davem@...emloft.net>,
        Larry Finger <Larry.Finger@...inger.net>,
        David Laight <David.Laight@...lab.com>,
        Christoph Hellwig <hch@...radead.org>
Cc:     linux-wireless@...r.kernel.org,
        Linux Netdev List <netdev@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Linux Upstreaming Team <linux@...lessm.com>,
        Daniel Drake <drake@...lessm.com>, stable@...r.kernel.org
Subject: Re: [PATCH v4 2/2] rtw88: pci: Use DMA sync instead of remapping in
 RX ISR

Jian-Hong Pan <jian-hong@...lessm.com> 於 2019年7月11日 週四 下午1:25寫道：
>
> 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-hong@...lessm.com>
> Cc: <stable@...r.kernel.org>
> ---

Sorry, also forget to place the version difference here

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.

v4:
 - Same as v3.

>  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 c415f5e94fed..68fae52151dd 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
>