[U-Boot] usb_test_unit_ready called every block read - performance

Marek Vasut
2012-07-30T23:41:52Z

Dear Jim Shimer,

> Marek,
>
> I don't have a USB 1.x device to do that regression. Taking the call to
> usb_test_unit_ready out of the block reads/writes and leaving it only in
> get info really speed up ext2load. With the recent cache changes on top of
> this and the 5ms delay, we're getting fairly close to the Linux USB
> transfer times and are happy with the results. Can you look into
> integrating this?

Can you send a patch that'll yank it out? I should be able to test it in a bit.

> -Jim
>
> On Mon, Jul 30, 2012 at 6:54 PM, Marek Vasut <marex@denx.de> wrote:
> > Dear Jim Shimer,
> >
> > > While tuning ext2load, we found that usb_test_unit_ready was being
> > > called every block read. We compared the usb block storage to the
> > > scsi block storage cmd_scsi.c, and found that the scsi device was only
> > > calling its scsi_setup_test_unit_ready() during scsi_can. It appears
> > > that usb_test_unit_ready() really only needs to be called once during
> > > usb_stor_scan(), via usb_stor_get_info(). Is there a particular
> > > reason usb_test_unit_ready is called for every block read, or do you
> > > think its
> >
> > ok
> >
> > > to only call during usb_stor_scan()? We're finding this speeds up
> >
> > ext2load
> >
> > > quite a bit.
> >
> > Could it be because the USB is actually quite slower than SCSI and the
> > device
> > might get congested? It seems the code was there ever since (I can't seem
> > to
> > find the origin of it) and we might actually want to try if this doesn't
> > break
> > some usb 1.x things.
> >
> > > Regards,
> > > Jim
> >
> > Best regards,
> > Marek Vasut

Best regards,
Marek Vasut