Hi,
On Fri, 30 Jun 2017 11:49:56 +0800 Bin Meng wrote:
> Hi,
>
> On Fri, Jun 23, 2017 at 5:54 PM, Bin Meng <bmeng...@gmail.com> wrote:
> > The only work we need do in usb_setup_descriptor() is to initialize
> > dev->descriptor.bMaxPacketSize0, when do_read is false. Other steps
> > are the same as do_read being true.
> >
> > While we are here, update the comment block to be within 80 cols.
> >
> > Signed-off-by: Bin Meng <bmeng...@gmail.com>
> > ---
> >
> > common/usb.c | 40 ++++++++++++++++++----------------------
> > 1 file changed, 18 insertions(+), 22 deletions(-)
> >
> > diff --git a/common/usb.c b/common/usb.c
> > index 15e1e4c..293d968 100644
> > --- a/common/usb.c
> > +++ b/common/usb.c
> > @@ -962,37 +962,33 @@ static int usb_setup_descriptor(struct usb_device
> > *dev, bool do_read)
> > * some more, or keeps on retransmitting the 8 byte header.
> > */
> >
> > - if (dev->speed == USB_SPEED_LOW) {
> > - dev->descriptor.bMaxPacketSize0 = 8;
> > - dev->maxpacketsize = PACKET_SIZE_8;
> > - } else {
> > - dev->descriptor.bMaxPacketSize0 = 64;
> > - dev->maxpacketsize = PACKET_SIZE_64;
> > - }
> > - dev->epmaxpacketin[0] = dev->descriptor.bMaxPacketSize0;
> > - dev->epmaxpacketout[0] = dev->descriptor.bMaxPacketSize0;
> > -
> > if (do_read) {
> > int err;
> >
> > /*
> > - * Validate we've received only at least 8 bytes, not that
> > we've
> > - * received the entire descriptor. The reasoning is:
> > - * - The code only uses fields in the first 8 bytes, so
> > that's all we
> > - * need to have fetched at this stage.
> > - * - The smallest maxpacket size is 8 bytes. Before we know
> > the actual
> > - * maxpacket the device uses, the USB controller may only
> > accept a
> > - * single packet. Consequently we are only guaranteed to
> > receive 1
> > - * packet (at least 8 bytes) even in a non-error case.
> > + * Validate we've received only at least 8 bytes, not that
> > + * we've received the entire descriptor. The reasoning is:
> > + * - The code only uses fields in the first 8 bytes, so
> > that's
> > + * all we need to have fetched at this stage.
> > + * - The smallest maxpacket size is 8 bytes. Before we know
> > + * the actual maxpacket the device uses, the USB
> > controller
> > + * may only accept a single packet. Consequently we are
> > only
> > + * guaranteed to receive 1 packet (at least 8 bytes) even
> > in
> > + * a non-error case.
> > *
> > - * At least the DWC2 controller needs to be programmed with
> > the number
> > - * of packets in addition to the number of bytes. A request
> > for 64
> > - * bytes of data with the maxpacket guessed as 64 (above)
> > yields a
> > - * request for 1 packet.
> > + * At least the DWC2 controller needs to be programmed with
> > + * the number of packets in addition to the number of bytes.
> > + * A request for 64 bytes of data with the maxpacket guessed
> > + * as 64 (above) yields a request for 1 packet.
> > */
> > err = get_descriptor_len(dev, 64, 8);
> > if (err)
> > return err;
> > + } else {
> > + if (dev->speed == USB_SPEED_LOW)
> > + dev->descriptor.bMaxPacketSize0 = 8;
> > + else
> > + dev->descriptor.bMaxPacketSize0 = 64;
> > }
> >
> > dev->epmaxpacketin[0] = dev->descriptor.bMaxPacketSize0;
> > --
>
> For some reason that I don't understand, this patch breaks EHCI.
> dev->maxpacketsize is equal to zero with this patch, which leads to a
> 'divide error' exception in ehci_submit_async(). Not sure if anyone
> has some hints?
>
In the do_read case the dev->descriptor.bMaxPacketSize0 is not set up.
Lothar Waßmann
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