Re: [PATCH 1/2] dma: Add interface to calculate data transferred

Vinod Koul
2013-10-16T06:31:59Z

On Tue, Oct 15, 2013 at 08:55:20AM -0700, Dan Williams wrote:
> On Tue, Oct 15, 2013 at 11:31 AM, Youquan Song
> <youquan.song@linux.intel.com> wrote:
> > On Sun, Oct 13, 2013 at 08:56:33PM +0530, Vinod Koul wrote:
> >> On Fri, Oct 11, 2013 at 06:33:43AM -0700, Greg KH wrote:
> >> > On Fri, Oct 11, 2013 at 05:42:17PM -0400, Youquan Song wrote:
> > The issue is that when I using UART to transfer data between to COMs
> > which using Designware DMA controller channel. But I check the specific
> > DMA channel by "cat /sys/class/dma/dma0chan3/bytes_transferred", but it
> > should all "0". I have transferred data by UART port, why its DMA
> > channel report "0" bytes transferred? So I guess that it is possible
> > the DMA device driver issue or the data does not use the Designware DMA channel
> > fro transferred. After check the code, I notice only when the DMA
> > channel used by network device driver and it will record how much data has been
> > tranferred, why other device driver will not calculate it. Since DMA
> > channel is used by other device driver, why only network is specific? since it is
> > common interface, the current /sys/class/dma/dma0chan*/bytes_transferred has
> > much possibility to mislead the user.
>
> Yes, and for that reason I think we should delete "
> /sys/class/dma/dma0chan*/bytes_transferred" it really serves no useful
> purpose besides "is my dma channel working" which can be determined by
> other means.
Well am going to take it a bit further and ask you why do we need the
/sys/class/dma? I have never used it for slave work.

Does it get used anywhere in async_tx?

--
~Vinod