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

Dan Williams
2013-10-15T15:55:26Z

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.

--
Dan