[PATCH] dwc_otg: Reduce interrupt load

[Sebastian Huber]

On 30/10/15 15:53, Hans Petter Selasky wrote:
> On 10/30/15 14:38, Sebastian Huber wrote:
>> Tested on an Altera Cyclone V development kit.  Here the controller has
>> 16 host channels.  This change significantly reduced the time spent in
>> the dwc_otg_interrupt_poll_locked() function.
>
> Hi,
>
> Thank you for your optimisation patch:
>
> https://svnweb.freebsd.org/changeset/base/290195

Thanks.

>
>
> How does the DWC OTG driver from FreeBSD work with your setup? 

After an update of the USB stack from 9.3 to current it worked out of 
the box. Thanks a lot for your great USB stack!

It seems that this driver doesn't support DMA. I see a quite high CPU 
utilization in this area:

static void
dwc_otg_interrupt_poll_locked(struct dwc_otg_softc *sc)
{
[...]
         if (sc->sc_last_rx_status != 0) {
[...]
             temp = GRXSTSRD_BCNT_GET(
                 sc->sc_last_rx_status);
             ep_no = GRXSTSRD_CHNUM_GET(
                 sc->sc_last_rx_status);

             /* receive data, if any */
             if (temp != 0) {
                 DPRINTF("Reading %d bytes from ep %d\n", temp, ep_no);
                 bus_space_read_region_4(sc->sc_io_tag, sc->sc_io_hdl,
                     DOTG_DFIFO(ep_no),
                     sc->sc_rx_bounce_buffer, (temp + 3) / 4);
             }

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
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E-Mail  : sebastian.huber at embedded-brains.de
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