USB DMA memory Allocation

[Hans Petter Selasky]

Hi,

On 08/12/13 03:19, aseem.jolly wrote:
>          if (EHCI_HCC_64BIT(cparams)) {
>                  DPRINTF("HCC uses 64-bit structures\n");
>
>                  /* MUST clear segment register if 64 bit capable */
>                  EWRITE4(sc, EHCI_CTRLDSSEGMENT, 0);
>          }
>          sc->sc_bus.usbrev = USB_REV_2_0;
>
>          /* Reset the controller */
>          DPRINTF("%s: resetting\n", device_get_nameunit(sc->sc_bus.bdev));
>
>          err = ehci_hcreset(sc);
>
> Doubt 1) Whats the need to clear 'CTRLDSSEGMENT' register when host
> controller reset is going to set it to
> default value(0x00000000) anyways. I think we should move this code to after
> reset or before we turn on the controller.

You cannot assume this, unless it is written somewhere.

>
> Doubt 2) We should be using EOWRITE4(sc, EHCI_CTRLDSSEGMENT, 0); instead of
> EWRITE4(sc, EHCI_CTRLDSSEGMENT, 0);

You are right!

http://svnweb.freebsd.org/changeset/base/254238

>
>
> #define EOWRITE4(sc, a, x)                                              \
>              bus_space_write_4((sc)->sc_io_tag, (sc)->sc_io_hdl,
> (sc)->sc_offs+(a), (x))
> #define EWRITE4(sc, a, x)                                               \
>              bus_space_write_4((sc)->sc_io_tag, (sc)->sc_io_hdl, (a), (x))
>

--HPS