Re: [PATCH next v2 3/6] usb: xhci-mtk: update fs bus bandwidth by bw_budget_table

[Chunfeng Yun (云春峰)]

On Mon, 2021-08-30 at 11:49 +0800, Ikjoon Jang wrote:
> On Fri, Aug 27, 2021 at 5:49 PM Chunfeng Yun (云春峰)
> <Chunfeng.Yun@xxxxxxxxxxxx> wrote:
> > 
> > On Fri, 2021-08-27 at 17:14 +0800, Ikjoon Jang wrote:
> > > On Fri, Aug 27, 2021 at 2:49 PM Chunfeng Yun (云春峰)
> > > <Chunfeng.Yun@xxxxxxxxxxxx> wrote:
> > > > 
> > > > On Thu, 2021-08-26 at 19:54 +0800, Ikjoon Jang wrote:
> > > > > Hi Chunfeng,
> > > > > 
> > > > > On Thu, Aug 26, 2021 at 10:52 AM Chunfeng Yun <
> > > > > chunfeng.yun@xxxxxxxxxxxx> wrote:
> > > > > > 
> > > > > > Use @bw_budget_table[] to update fs bus bandwidth due to
> > > > > > not all microframes consume @bw_cost_per_microframe, see
> > > > > > setup_sch_info().
> > > > > > 
> > > > > > Signed-off-by: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>
> > > > > > ---
> > > > > > v2: new patch, move from another series
> > > > > > ---
> > > > > >  drivers/usb/host/xhci-mtk-sch.c | 17 +++++++----------
> > > > > >  1 file changed, 7 insertions(+), 10 deletions(-)
> > > > > > 
> > > > > > diff --git a/drivers/usb/host/xhci-mtk-sch.c
> > > > > > b/drivers/usb/host/xhci-mtk-sch.c
> > > > > > index cffcaf4dfa9f..83abd28269ca 100644
> > > > > > --- a/drivers/usb/host/xhci-mtk-sch.c
> > > > > > +++ b/drivers/usb/host/xhci-mtk-sch.c
> > > > > > @@ -458,8 +458,8 @@ static int check_fs_bus_bw(struct
> > > > > > mu3h_sch_ep_info *sch_ep, int offset)
> > > > > >                  * Compared with hs bus, no matter what ep
> > > > > > type,
> > > > > >                  * the hub will always delay one uframe to
> > > > > > send
> > > > > > data
> > > > > >                  */
> > > > > > -               for (j = 0; j < sch_ep->cs_count; j++) {
> > > > > > -                       tmp = tt->fs_bus_bw[base + j] +
> > > > > > sch_ep-
> > > > > > > bw_cost_per_microframe;
> > > > > > 
> > > > > > +               for (j = 0; j < sch_ep-
> > > > > > >num_budget_microframes;
> > > > > > j++) {
> > > > > > +                       tmp = tt->fs_bus_bw[base + j] +
> > > > > > sch_ep-
> > > > > > > bw_budget_table[j];
> > > > > 
> > > > > I'm worrying about this case with two endpoints,
> > > > > * EP1OUT: isochronous, maxpacket=192: bw_budget_table[] = {
> > > > > 188,
> > > > > 188,
> > > > > 0, ... }
> > > > > * EP2IN: interrupt, maxpacket=64: bw_budget_table[] = { 0, 0,
> > > > > 64,
> > > > > 64,
> > > > > ... }
> > > > > (Is this correct bw_budget_table contents for those eps?)
> > > > 
> > > > Yes, ep1out isoc use two uframe, ep2in intr use a extra cs;
> > > > > 
> > > > > I'm not sure if it's okay for those two endpoints to be
> > > > > allocated
> > > > > on the same u-frame slot.
> > > > > Can you please check if this is okay for xhci-mtk?
> > > > 
> > > > Already test it this afternoon, can transfer data rightly on
> > > > our
> > > > dvt
> > > > env.
> > > > 
> > > > > (I feel like I already asked the same questions many times.)
> > > > 
> > > > Yes, as said before, prefer to use bw_budget_table[], if there
> > > > is
> > > > issue, we can fix it by building this table.
> > > 
> > > So do you mean such an allocation shouldn't be a problem by IP
> > > design?
> > 
> > Yes, at least on our dvt platform
> 
> Did you check that your side also has a similar allocation
> (SSPLIT-all sits between SSPLIT-start ~ -end for another ep)?
> My audio headset doesn't work properly with this scheme.
> 
> > 
> > > 
> > > This patch starts to allow such an allocation (again).
> > > But i remember my earlier tests showed that when those two eps
> > > in the above example are allocated on the same u-frame slot,
> > > xhci-mtk puts "SSPLIT for EP2" between
> > > "SSPLIT-start and SSPLIT-end for EP1OUT transaction",
> > > which is a spec violation.
> > 
> > Which section in usb2.0 spec?
> 
> I think that's just a basic rule - if software wants to send 192
> bytes
> through a full-speed bus, HC should send OUT/DATA 192 bytes
> continuously without inserting any other packets during that 192
> bytes.
> and usb2 11.14.2 mentions that TT has separated
> Start-Split and Complete-Split buffers
> but not tracked each transaction per endpoint basis.
> 
> > 
> > > Hub will generate bit stuffing errors on the
> > > full-speed bus.
> > 
> > which platform?
> 
> I remember it was mt8173.
Does it happen on mt8192?

> 
> And for bit stuffing errors I mentioned in the earlier mail.
> when I read the spec again, 11.21 mentions that bit stuffing error
> is generated when _a microframe_ should be passed without
> corresponding SSPLIT-mid/end. So this is not the case and also
> I'm not sure what will happen on the full-speed bus, sorry.
> In my case what I can be sure of is that the audio output was
> broken with those allotments.
> 
> What is the xhci-mtk's policy when there are more than two EPs
> marked as the same u-frame offset like in the above example?
Seems no this limitation, an EP doesn't monopolize an u-frame

> 
> > 
> > > 
> > > 
> > > > 
> > > > Thanks
> > > > > 
> > > > > 
> > > > > >                         if (tmp > FS_PAYLOAD_MAX)
> > > > > >                                 return -ESCH_BW_OVERFLOW;
> > > > > >                 }
> > > > > > @@ -534,21 +534,18 @@ static void update_sch_tt(struct
> > > > > > mu3h_sch_ep_info *sch_ep, bool used)
> > > > > >  {
> > > > > >         struct mu3h_sch_tt *tt = sch_ep->sch_tt;
> > > > > >         u32 base, num_esit;
> > > > > > -       int bw_updated;
> > > > > >         int i, j;
> > > > > > 
> > > > > >         num_esit = XHCI_MTK_MAX_ESIT / sch_ep->esit;
> > > > > > 
> > > > > > -       if (used)
> > > > > > -               bw_updated = sch_ep-
> > > > > > >bw_cost_per_microframe;
> > > > > > -       else
> > > > > > -               bw_updated = -sch_ep-
> > > > > > >bw_cost_per_microframe;
> > > > > > -
> > > > > >         for (i = 0; i < num_esit; i++) {
> > > > > >                 base = sch_ep->offset + i * sch_ep->esit;
> > > > > > 
> > > > > > -               for (j = 0; j < sch_ep->cs_count; j++)
> > > > > > -                       tt->fs_bus_bw[base + j] +=
> > > > > > bw_updated;
> > > > > > +               for (j = 0; j < sch_ep-
> > > > > > >num_budget_microframes;
> > > > > > j++)
> > > > > > +                       if (used)
> > > > > > +                               tt->fs_bus_bw[base + j] +=
> > > > > > sch_ep-
> > > > > > > bw_budget_table[j];
> > > > > > 
> > > > > > +                       else
> > > > > > +                               tt->fs_bus_bw[base + j] -=
> > > > > > sch_ep-
> > > > > > > bw_budget_table[j];
> > > > > > 
> > > > > >         }
> > > > > > 
> > > > > >         if (used)
> > > > > > --
> > > > > > 2.18.0
> > > > > >