linux-kernel - Re: [PATCH 08/11] usb: xhci-mtk: update fs bus bandwidth by bw_budget

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Date:   Wed, 4 Aug 2021 22:06:21 +0800
From:   Ikjoon Jang <ikjn@...omium.org>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-usb@...r.kernel.org,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Eddie Hung <eddie.hung@...iatek.com>
Subject: Re: [PATCH 08/11] usb: xhci-mtk: update fs bus bandwidth by bw_budget_table

Hi,

On Wed, Aug 4, 2021 at 1:19 PM Chunfeng Yun <chunfeng.yun@...iatek.com> wrote:
>
> On Tue, 2021-08-03 at 14:05 +0800, Ikjoon Jang wrote:
> > Hi Chunfeng,
> >
> > On Fri, Jul 30, 2021 at 4:51 PM Chunfeng Yun <chunfeng.yun@...iatek.com> 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@...iatek.com>
> > > ---
> > >  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 0bb1a6295d64..10c0f0f6461f 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];
> > >                         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];
> >
> > I agree that xhci-mtk-sch still has more rooms for tt periodic bandwidth
> > but I think this approach could trigger a problem.
> See updat_bus_bw(), when add fs ep's bandwidth, it uses
> bw_budget_table[], so prefer to use the same way
>
> >
> > for example, if there are two endpoints scheduled in the same u-frame index,
> > * ep1out  = iso 192bytes bw_budget_table[] = { 188, 188, 0, ...} --> y0
> > * ep2in = int 64bytes, bw_budget_table[] = { 0, 0, 64, ... }  --> y0
> >
> > (If this is possible allocation from this patch),
> > I guess xhci-mtk could have some problems on internal scheduling?
>
> Test it on dvt env. don't encounter issues;
>

As you can see In the above example, this patch starts to allow that allocation.
Do you mean that we don't have to worry about such a case (on all MTK
platforms)?

thanks

> Thanks
>
> >
> > >         }
> > >
> > >         if (used)
> >
> > > --
> > > 2.18.0
> > >
>