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

[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?

-Jim

On Mon, Jul 30, 2012 at 6:54 PM, Marek Vasut <marex at 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
>



-- 
*James H Shimer*
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