[U-Boot] XHCI behavior

Bin Meng bmeng.cn at gmail.com
Sat Sep 7 03:59:00 UTC 2019

Hi Aaron,

On Sat, Sep 7, 2019 at 11:08 AM Aaron Williams <awilliams at marvell.com> wrote:
> Hi,
> I am seeing crashes in our XHCI implementation based on a Designware USB 3.1
> core. One thing I noticed is that this core sets the PAE bit in the HCCparams.
> The result of this is that when there is a short packet and there are two TDs,
> then when PAE is set there will be two responses with the second one being
> success. I'm still not sure if the length field I'm seeing is correct or not,
> but it appears that neither Linux nor U-Boot can handle HCs with the PAE bit
> set. See the eXtendable Host Controller Interface 1.1 sections and
> 5.3.6.

It looks this PAE bit was introduced in spec 1.1. U-Boot xHCI driver
was ported from an earlier version of Linux xHCI driver, and I doubt
it could correctly handle it. But you mentioned that Linux could not
handle HCs with PAE set. Did you try the latest kernel?

> With short packets with the PAE bit set with to TRBs I get two responses when
> the data fits in the first TRB. The first event TRB contains a short packet
> response with the length set to the amount of space within the first TRB that
> is actually used. The second TRB event is a success completion code, as is
> described in section
> Personally I find this PAE bit a major pain in the arse that causes more
> trouble than it's worth.


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