[U-Boot] [PATCH 03/16] usb: Remove unnecessary work in usb_setup_descriptor()

[Lothar Waßmann]

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.cn at 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.cn at 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