On Fri, Oct 05, 2018 at 12:07:06PM +0000, Tony Chuang wrote:
> > > +static void rtw_pci_dma_check(struct rtw_dev *rtwdev,
> > > + struct rtw_pci_rx_ring *rx_ring,
> > > + u32 idx)
> > > +{
> > > + struct rtw_chip_info *chip = rtwdev->chip;
> > > + struct rtw_pci_rx_buffer_desc *buf_desc;
> > > + u32 desc_sz = chip->rx_buf_desc_sz;
> > > + u16 total_pkt_size;
> > > + int i;
> > > +
> > > + buf_desc = (struct rtw_pci_rx_buffer_desc *)(rx_ring->r.head +
> > > + idx * desc_sz);
> > > + for (i = 0; i < 20; i++) {
> > > + total_pkt_size = le16_to_cpu(buf_desc->total_pkt_size);
> > > + if (total_pkt_size)
> > > + return;
> > > + }
> > > +
> > > + if (i >= 20)
> > > + rtw_warn(rtwdev, "pci bus timeout, drop packet\n");
> > This is not right, most likely you need to use
> > dma_sync_single_for_cpu() .
>
> Not really understand how dma_sync_single_for_cpu() works.
> Can you show me if possible?
dma_sync_single_for_cpu() and dma_sync_single_for_device()
transfer dma buffer ownership to respectivly CPU and device.
It is well documented in:
Documentation/DMA-API-HOWTO.txt:
Documentation/DMA-API.txt
Thanks
Stanislaw
