Re: [PATCH 1/2 v2] dmaengine: rcar-dmac: ensure CHCR DE bit is actually 0 after clear

[Geert Uytterhoeven]

Hi Morimoto-san,

On Fri, Nov 17, 2017 at 1:10 AM, Kuninori Morimoto
<kuninori.morimoto.gx@xxxxxxxxxxx> wrote:
>> > +static void rcar_dmac_chcr_de_barrier(struct rcar_dmac_chan *chan)
>> > +{
>> > +       u32 chcr;
>> > +       int i;
>>
>> unsigned int
>>
>> > +
>> > +       /*
>> > +        * Ensure that the setting of the DE bit is actually 0 after
>> > +        * clearing it.
>> > +        */
>> > +       for (i = 0; i < 1024; i++) {
>> > +               chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
>> > +               if (!(chcr & RCAR_DMACHCR_DE))
>> > +                       return;
>> > +               udelay(1);
>> > +       }
>>
>> What's a typical number of loops needed before DE is really cleared?
>
> It case by case, but I don't want to use while(1) loop

I understand that, and I agree wholeheartedly with limiting the number
of cycles.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds