[U-Boot] usb_stor_BBB_transport 5 ms delay - performance

[Jim Shimer]

With the code that skips the 5 msecond delay if the device is ready, my fat
load time went from 80 seconds to 8 seconds.  This is actually fairly close
to what it takes to do the same transfer in Linux (5 seconds).  So I assume
the 5 msdelay when the device is already ready is not necessary.

On Thu, Jul 26, 2012 at 8:43 PM, Benoît Thébaudeau <
benoit.thebaudeau at advansee.com> wrote:

> Hi Jim,
>
> On Thu, Jul 26, 2012 at 10:20:48 PM, Jim Shimer wrote:
> > I'm seeing a 5ms delay in usb_stor_BBB_transport, which occurs every
> > 10K of
> > data for fatload usb or 500ms of delay per 1MB of image size.  This
> > adds up
> > to quite a bit of delay if you're loading a large ramdisk.
> >
> > Does anyone know what the reason for the 5ms delay really is?  I'm
> > assuming
> > that this delay is to debounce the 5V/100ma USB power up.  I made
> > some
> > modification, where the delay is skipped if the device has already
> > been
> > queried as ready.  This has save me 500ms/M on fatload times (eg,
> > 140M=70seconds).  Is there anything wrong with this tweak?
> >
> > Here's a diff of what I've done to get the performance I need:
> >
> > --- usb_storage.c.orig  2012-07-26 16:06:40.775251000 -0400
> > +++ usb_storage.c       2012-07-26 13:49:36.000000000 -0400
> > @@ -132,6 +132,7 @@ static block_dev_desc_t usb_dev_desc[USB
> >  struct us_data;
> >  typedef int (*trans_cmnd)(ccb *cb, struct us_data *data);
> >  typedef int (*trans_reset)(struct us_data *data);
> > +typedef enum us_status { USB_NOT_READY, USB_READY} us_status;
> >
> >  struct us_data {
> >         struct usb_device *pusb_dev;     /* this usb_device */
> > @@ -154,6 +155,7 @@ struct us_data {
> >         ccb             *srb;                   /* current srb */
> >         trans_reset     transport_reset;        /* reset routine */
> >         trans_cmnd      transport;              /* transport routine
> >         */
> > +       us_status       status;
> >  };
> >
> >  static struct us_data usb_stor[USB_MAX_STOR_DEV];
> > @@ -691,7 +693,10 @@ int usb_stor_BBB_transport(ccb *srb, str
> >                 usb_stor_BBB_reset(us);
> >                 return USB_STOR_TRANSPORT_FAILED;
> >         }
> > -       wait_ms(5);
> > +       if(us->status != USB_READY)
> > +       {
> > +               wait_ms(5);
> > +       }
> >         pipein = usb_rcvbulkpipe(us->pusb_dev, us->ep_in);
> >         pipeout = usb_sndbulkpipe(us->pusb_dev, us->ep_out);
> >         /* DATA phase + error handling */
> > @@ -957,7 +962,10 @@ static int usb_test_unit_ready(ccb *srb,
> >                 srb->datalen = 0;
> >                 srb->cmdlen = 12;
> >                 if (ss->transport(srb, ss) ==
> >                 USB_STOR_TRANSPORT_GOOD)
> > +               {
> > +                       ss->status = USB_READY;
> >                         return 0;
> > +               }
> >                 usb_request_sense(srb, ss);
> >                 wait_ms(100);
> >         } while (retries--);
> > @@ -965,6 +973,11 @@ static int usb_test_unit_ready(ccb *srb,
> >         return -1;
> >  }
> >
> > +static void usb_set_unit_not_ready(struct us_data *ss)
> > +{
> > +       ss->status = USB_NOT_READY;
> > +}
> > +
> >  static int usb_read_capacity(ccb *srb, struct us_data *ss)
> >  {
> >         int retry;
> > @@ -1108,6 +1121,7 @@ retry_it:
> >                 blks -= smallblks;
> >                 buf_addr += srb->datalen;
> >         } while (blks != 0);
> > +       usb_set_unit_not_ready((struct us_data *)dev->privptr);
> >
> >         USB_STOR_PRINTF("usb_read: end startblk %lx, blccnt %x buffer
> > %lx\n",
> >                         start, smallblks, buf_addr);
> > @@ -1188,6 +1202,7 @@ retry_it:
> >                 blks -= smallblks;
> >                 buf_addr += srb->datalen;
> >         } while (blks != 0);
> > +       usb_set_unit_not_ready((struct us_data *)dev->privptr);
> >
> >         USB_STOR_PRINTF("usb_write: end startblk %lx, blccnt %x
> >         buffer
> > %lx\n",
> >                         start, smallblks, buf_addr);
> > @@ -1398,6 +1413,7 @@ int usb_stor_get_info(struct usb_device
> >                 cap[0] = 2880;
> >                 cap[1] = 0x200;
> >         }
> > +       usb_set_unit_not_ready((struct us_data *)dev->privptr);
> >         USB_STOR_PRINTF("Read Capacity returns: 0x%lx, 0x%lx\n",
> >         cap[0],
> >                         cap[1]);
> >  #if 0
> >
> >
> > I'd appreciate any feedback.
> > Regards
>
> I have not looked into this delay issue, but I had similar performance
> issues
> that I fixed with the following series:
> http://patchwork.ozlabs.org/patch/172052/
> http://patchwork.ozlabs.org/patch/172204/
> http://patchwork.ozlabs.org/patch/172054/
> http://patchwork.ozlabs.org/patch/172055/
> http://patchwork.ozlabs.org/patch/172056/
>
> Your suggestion is interesting and might be a complement to my series. I
> don't
> have time to check its correctness right now, but I'll try soon.
>
> Best regards,
> Benoît
>



-- 
*James H Shimer*
Motorola Mobility T3-12-HH72
900 Chelmsford Street
Lowell MA 08151
978-614-3550