[U-Boot] usb_stor_BBB_transport 5 ms delay - performance

[Jim Shimer]

I agree with everything, its up to you how to apply the change.

I did see a flags field but thought having a new one was conservative (I
had no real reason to have a new field).   As for the typecasts I was
following the API which tests for device ready (Monkey See Monkey Do).
Also I have no compelling reason to need a "setter function" either.  I
have no compelling feelings towards the implementation other than the 5ms
adds an unnecessary delay when the device is already known to be ready, and
this delay accumulates to a very poor performance for large files.

Thanks for working on this!

On Fri, Jul 27, 2012 at 11:06 AM, Marek Vasut <marex at denx.de> wrote:

> Dear Benoît Thébaudeau,
>
> > 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;
>
> Can we possibly avoid the typedef?
>
> > >  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;
>
> Don't we have some flags for it already?
>
> > >
> > >  };
> > >
> > >  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;
> > > +}
> > > +
>
> We don't need a setter function really.
>
> > >  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);
>
> I think we should be much more careful about these typecasts.
>
> > >         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);
>
> Same here.
>
> > >         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);
>
> The rest is cool.
> [...]
>



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