On Tue, Sep 25, 2012 at 2:19 PM, Sarah Sharp
<sarah.a.sharp@xxxxxxxxxxxxxxx> wrote:
> On Tue, Sep 25, 2012 at 09:26:00AM +0300, Adrian Sandu wrote:
>> On Tue, Sep 25, 2012 at 12:38 AM, Sarah Sharp
>> <sarah.a.sharp@xxxxxxxxxxxxxxx> wrote:
>> > Ok, so 3.4.11 doesn't work, and the log file was from 3.5.
>>
>> If you want I can provide a 3.4 log...
>
> Hmm, does a 3.3 stable kernel work for you? I have a hypothesis.
>
> Alan, I'm wondering if the xHCI ring expansion is causing issues with
> USB hard drives under xHCI. Testing with a Buffalo USB 3.0 hard drive
> with an NEC uPD720200 xHCI host, I see that the usb-storage and SCSI
> initialization produces I/O errors on random sectors in 3.4.0, 3.4.6,
> and 3.5.0. I can't get those errors to be reproduced in 3.3.1.
Do you see the ring get expanded(more than 2 segments) when the errors occur?
>
> The xHCI ring expansion was added in 3.4, and we changed the xHCI's
> sg_tablesize:
>
> int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
> {
> ...
> /* Accept arbitrarily long scatter-gather lists */
> hcd->self.sg_tablesize = ~0;
Actually this line is copied from ehci-hcd.
Thanks,
Andiry
>
> The usb-storage driver sets the tablesize thus:
>
> static unsigned int usb_stor_sg_tablesize(struct usb_interface *intf)
> {
> struct usb_device *usb_dev = interface_to_usbdev(intf);
>
> if (usb_dev->bus->sg_tablesize) {
> return usb_dev->bus->sg_tablesize;
> }
> return SG_ALL;
> }
>
> I notice that SG_ALL is set to SCSI_MAX_SG_SEGMENTS, which is only 128.
> Should we be passing an arbitrarily large number to the SCSI core?
> There's some wording in include/scsi/scsi.h about also limiting the
> number of chained sgs to 2048. I'm wondering if we're hitting some bugs
> in the SCSI layer because we're setting the sg_tablesize so high.
>
> Alternately, we could be hitting bugs in the USB 3.0 firmware when we
> attempt to issue a read or write that's too big. The read on Adrian's
> hard drive failed on a bigger read request (122880 bytes). It would be
> interesting to see if it works fine if the xHCI sg_tablesize is limited.
> I'm going to try that with my own drive on 3.5.4 and see if it helps.
>
> Sarah Sharp
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