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

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Date:   Tue, 10 Aug 2021 01:45:16 +0000
From:   Chunfeng Yun (云春峰) 
        <Chunfeng.Yun@...iatek.com>
To:     "ikjn@...omium.org" <ikjn@...omium.org>
CC:     "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mathias.nyman@...el.com" <mathias.nyman@...el.com>,
        Eddie Hung (洪正鑫) 
        <Eddie.Hung@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>
Subject: Re: [PATCH 08/11] usb: xhci-mtk: update fs bus bandwidth by
 bw_budget_table

On Wed, 2021-08-04 at 22:06 +0800, Ikjoon Jang wrote:
> 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)?
No, that is another question, when update bus_bw[] and fs_bus_bw[] for
FS with TT should use the same bw_budget_table[] which is filled in
setup_sch_info(). If the bw_budget_table[] is something wrong, we can
prepare new patch to fix it.

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