Re: [RESEND PATCH 1/6] dma: rcar-dma: add wait after stopping dma engine

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Hello.

On 09/21/2015 02:30 PM, Hamza Farooq wrote:

>>> +#define NR_READS_TO_WAIT (5) /* number of times to check if DE = 0 */
>>
>>     Parens not needed. (I'm seeing this patchset for the first time.)

> They prevent funny things from happening so I use them all the time.

    No, they don't in this case.

> First time when I sent the patch-set, I had missed linux-sh mailing
> list.
> Here's the link from dmaengine mailing list in case you're interested
> http://www.spinics.net/lists/dmaengine/msg06103.html

    Thanks for the link.

>>> +static inline int rcar_dmac_wait_stop(struct rcar_dmac_chan *chan)
>>> +{
>>> +       unsigned int i = 0;
>>> +
>>> +       do {
>>> +               u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
>>> +
>>> +               if (!(chcr & RCAR_DMACHCR_DE))
>>> +                       return 0;
>>> +               cpu_relax();
>>> +               dev_dbg(chan->chan.device->dev, "DMA xfer couldn't be stopped");
>>> +       } while (++i < NR_READS_TO_WAIT);
>>
>>     Hm, this can be a *for* loop, no?

> Could you explain why would you prefer a for loop here? do..while
> makes sure even if NR_READS_TO_WAIT is set to 0, the stop action takes
> place

    Hm, this doesn't make sense to me. If # of reads is 0, we shouldn't read, no?

>>   Please don't change the existing indentation, it doesn't seem like you're changing anything else here

> ok. How should I send the updates patch though, through replying to
> this email or a new thread?

    New thread I think.

> Thanks!
> Hamza

MBR, Sergei