Re: [Qemu-devel] [PATCH 1/2 v5-test] add function DMA_set_return and DMA_set_channel_async in dma.c

[Zhi Hui Li]

> > +
> > +void DMA_set_return(int nret, int nchan)
> > +{
> > +    struct dma_regs *r;
> > +    struct dma_cont *d;
> > +    int icont, ichan;
> > +
> > +    icont = nchan>  3;
> > +    ichan = nchan&  3;
> > +    d = dma_controllers;
> > +    r =&d[icont].regs[ichan];
> > +    r->now[COUNT] = nret;
> > +    assert(r->channel_is_asynchronous);
> > +    assert(r->channel_running);
>
> Thanks, this is very much like what I had in mind, except that here I
> would have called DMA_run.  Also you can then remove the bottom half
> (and rearm logic) completely.
>
> If calling DMA_run is not working, perhaps it is because you didn't
> remove the bottom half.

You have written to me :

   assert(channel_is_asynchronous[ichan]);
   assert(channel_running[ichan] == 1);
   channel_running[ichan]--;
   if ((0 == (d->mask & mask)) && (0 != (d->status & (mask << 4)))) {
       channel_run (icont, ichan);
   }

If I add the code :
   if ((0 == (d->mask & mask)) && (0 != (d->status & (mask << 4)))) {
       channel_run (icont, ichan);
   }
Because function DMA_set_return is called in fdctrl_read_DMA_cb and 
fdctrl_write_DMA_cb, the fdctrl_stop_transfer will release the channel,
but fdctrl_stop_transfer is after the DMA_set_return, so the channel_run 
will run again, so here I delete the above code.

> I would hope that you can also change the "if (running) goto out;" to an
> "assert(!running)", but I'm not so sure.

sorry, here I don't understand well,or you can explain in detail.  :)


Thank you very much for your feedback!   :)