Re: [RFC v2 03/12] rtw88: hci files

[Stanislaw Gruszka <sgruszka@redhat.com>]

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