On Thu, 2021-08-12 at 17:31 +0800, Ikjoon Jang wrote:
> HI,
>
> On Wed, Aug 11, 2021 at 5:02 PM Chunfeng Yun (云春峰)
> <Chunfeng.Yun@xxxxxxxxxxxx> wrote:
> >
> > On Mon, 2021-08-09 at 17:42 +0800, Ikjoon Jang wrote:
> > > On Mon, Aug 9, 2021 at 5:11 PM Greg Kroah-Hartman
> > > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > > >
> > > > On Mon, Aug 09, 2021 at 04:59:29PM +0800, Ikjoon Jang wrote:
> > > > > xhci-mtk has 64 slots for periodic bandwidth calculations and
> > > > > each
> > > > > slot represents byte budgets on a microframe. When an
> > > > > endpoint's
> > > > > allocation sits on the boundary of the table, byte budgets'
> > > > > slot
> > > > > should be rolled over but the current implementation doesn't.
> > > > >
> > > > > This patch applies a 6 bits mask to the microframe index to
> > > > > handle
> > > > > its rollover 64 slots and prevent out-of-bounds array access.
> > > > >
> > > > > Signed-off-by: Ikjoon Jang <ikjn@xxxxxxxxxxxx>
> > > > > ---
> > > > >
> > > > > drivers/usb/host/xhci-mtk-sch.c | 79 +++++++++------------
> > > > > ----
> > > > > --------
> > > > > drivers/usb/host/xhci-mtk.h | 1 +
> > > > > 2 files changed, 23 insertions(+), 57 deletions(-)
> > > >
> > > > Why is this "RFC"? What needs to be addressed in this change
> > > > before it
> > > > can be accepted?
> > >
> > > sorry, I had to mention why this is RFC:
> > >
> > > I simply don't know about the details of the xhci-mtk internals.
> > > It was okay from my tests with mt8173 and I think this will be
> > > harmless
> > > as this is "better than before".
> > >
> > > But when I removed get_esit_boundary(), I really have no idea why
> > > it was there. I'm wondering if there was another reason of that
> > > function
> > > other than just preventing out-of-bounds. Maybe chunfeng can
> > > answer
> > > this?
> >
> > We use @esit to prevent out-of-bounds array access. it's not a
> > ring,
> > can't insert out-of-bounds value into head slot.
>
> Thanks, so that function was only for out-of-bounds array access.
> then I think we just can remove that function and use it as a ring.
> Can you tell me _why_ it can't be used as a ring?
Treat it as a period, roll over slot equals to put it into the next
period.
>
> I think a transaction (e.g. esit_boundary = 7) can start its first
> SSPLIT
> from Y_7 (offset = 7). But will that allocation be matched with this?
>
> - if ((offset + sch_ep->num_budget_microframes) >
> esit_boundary)
> - break;
>
> I mean I'm not sure why this is needed.
Prevent out-of-bounds.
>
> Until now, I couldn't find a way to accept the USB audio headset
> with a configuration of { INT-IN 64 + ISOC-OUT 384 + ISOC-IN 192 }
> without this patch.
what is the interval value of each endpoint?
>
> >
> > >
> > > Thanks!
> > >
> > > >
> > > > thanks,
> > > >
> > > > greg k-h
