[Cbe-oss-dev] [PATCH 3/5] usb: PS3 EHCI QH read work-around

[Greg KH]

On Thu, Nov 17, 2011 at 02:44:36PM -0800, Geoff Levand wrote:
> On Tue, 2011-11-15 at 11:57 -0500, Alan Stern wrote:
> > On Tue, 15 Nov 2011, Geoff Levand wrote:
> > 
> > > PS3 EHCI HC errata fix 244.  The SCC EHCI HC will not correctly perform QH
> > > reads that occur near or span a micro-frame boundry.  This is due to a problem
> > > in the Nak Count Reload Control logic (EHCI Specification 1.0 Section 4.9.1).
> > > 
> > > The work-around for this problem is for the HC driver to set I=1 (inactive) for
> > > QHs with H=1 (list head).
> > > 
> > > diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
> > > index e43cb5a..4ff0b7e 100644
> > > --- a/drivers/usb/host/ehci-hcd.c
> > > +++ b/drivers/usb/host/ehci-hcd.c
> > > @@ -621,6 +621,7 @@ static int ehci_init(struct usb_hcd *hcd)
> > >  	hw->hw_next = QH_NEXT(ehci, ehci->async->qh_dma);
> > >  	hw->hw_info1 = cpu_to_hc32(ehci, QH_HEAD);
> > >  	hw->hw_info1 |= cpu_to_hc32(ehci, (2 << 28));	/* RL = 2 */
> > > +	hw->hw_info1 |= cpu_to_hc32(ehci, (1 << 7));	/* I = 1 */
> > >  	hw->hw_token = cpu_to_hc32(ehci, QTD_STS_HALT);
> > >  	hw->hw_qtd_next = EHCI_LIST_END(ehci);
> > >  	ehci->async->qh_state = QH_STATE_LINKED;
> > 
> > This should be okay, although the RL stuff isn't needed.  Have you 
> > tested it on desktop PCs?
> 
> No, I will try it and report.
> 
> Just as a side note, I would certainly appreciate if you could request
> any future desktop PC related changes be tested on a PS3...

Given that one can not install Linux on a PS3 anymore, that might be a
bit difficult :)

greg k-h