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Date:   Tue, 19 Jan 2021 10:33:14 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     Ikjoon Jang <ikjn@...omium.org>
CC:     Mathias Nyman <mathias.nyman@...ux.intel.com>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>, <linux-usb@...r.kernel.org>,
        Tianping Fang <tianping.fang@...iatek.com>,
        Zhanyong Wang <zhanyong.wang@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5] usb: xhci-mtk: fix unreleased bandwidth data

On Fri, 2021-01-15 at 10:51 +0800, Ikjoon Jang wrote:
> On Thu, Jan 14, 2021 at 4:30 PM Chunfeng Yun <chunfeng.yun@...iatek.com> wrote:
> >
> > Hi Ikjoon,
> >
> > On Tue, 2021-01-12 at 13:48 +0800, Ikjoon Jang wrote:
> > > On Fri, Jan 8, 2021 at 10:44 PM Mathias Nyman
> > > <mathias.nyman@...ux.intel.com> wrote:
> > > >
> > > > On 8.1.2021 8.11, Chunfeng Yun wrote:
> > > > > On Thu, 2021-01-07 at 13:09 +0200, Mathias Nyman wrote:
> > > > >> On 29.12.2020 8.24, Ikjoon Jang wrote:
> > > > >>> xhci-mtk has hooks on add_endpoint() and drop_endpoint() from xhci
> > > > >>> to handle its own sw bandwidth managements and stores bandwidth data
> > > > >>> into internal table every time add_endpoint() is called,
> > > > >>> so when bandwidth allocation fails at one endpoint, all earlier
> > > > >>> allocation from the same interface could still remain at the table.
> > > > >>>
> > > > >>> This patch adds two more hooks from check_bandwidth() and
> > > > >>> reset_bandwidth(), and make mtk-xhci to releases all failed endpoints
> > > > >>> from reset_bandwidth().
> > > > >>>
> > > > >>> Fixes: 08e469de87a2 ("usb: xhci-mtk: supports bandwidth scheduling with multi-TT")
> > > > >>> Signed-off-by: Ikjoon Jang <ikjn@...omium.org>
> > > > >>>
> > > > >>
> > > > >> ...
> > > > >>
> > > > >>>
> > > > >>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> > > > >>> index d4a8d0efbbc4..e1fcd3cf723f 100644
> > > > >>> --- a/drivers/usb/host/xhci.c
> > > > >>> +++ b/drivers/usb/host/xhci.c
> > > > >>> @@ -2882,6 +2882,12 @@ static int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
> > > > >>>     xhci_dbg(xhci, "%s called for udev %p\n", __func__, udev);
> > > > >>>     virt_dev = xhci->devs[udev->slot_id];
> > > > >>>
> > > > >>> +   if (xhci->quirks & XHCI_MTK_HOST) {
> > > > >>> +           ret = xhci_mtk_check_bandwidth(hcd, udev);
> > > > >>> +           if (ret < 0)
> > > > >>> +                   return ret;
> > > > >>> +   }
> > > > >>> +
> > > > >>
> > > > >> Just noticed that XHCI_MTK_HOST quirk is only set in xhci-mtk.c.
> > > > >> xhci-mtk.c calls xhci_init_driver(..., xhci_mtk_overrides) with a .reset override function.
> > > > >>
> > > > >> why not add override functions for .check_bandwidth and .reset_bandwidth to xhci_mtk_overrides instead?
> > > > >>
> > > > >> Another patch to add similar overrides for .add_endpoint and .drop_endpoint should probably be
> > > > >> done so that we can get rid of the xhci_mtk_add/drop_ep_quirk() calls in xhci.c as well
> > > > > You mean, we can export xhci_add/drop_endpoint()?
> > > >
> > > > I think so, unless you have a better idea.
> > > > I prefer exporting the generic add/drop_endpoint functions rather than the vendor specific quirk functions.
> > > >
> > >
> > > When moving out all MTK_HOST quirks and unlink xhci-mtk-sch from xhci,
> > > xhci-mtk-sch still needs to touch the xhci internals, at least struct
> > > xhci_ep_ctx.
> > >
> > > My naive idea is just let xhci export one more function to expose xhci_ep_ctx.
> > > But I'm not sure whether this is acceptable:
> > I find that xhci_add_endpoint() ignores some errors with return 0, for
> > these cases we needn't call xhci_mtk_add_ep-quirk(), so may be not a
> > good way to just export xhci_add_endpoint().
> 
> yeah, maybe that's from ep0 case?
> 
> And I've thought that we could also unlink xhci-mtk-sch from the xhci module
> if MTK_HOST quirk functions are moved out to mtk platform driver's overrides.
> I guess I've gone too far.
> 
> If we keep xhci-mtk-sch being built with the xhci module,
> xhci-mtk-sch can directly access input control context and its drop/add flags,
> so I think we can simply remove {add|drop}_endpoint() quirks and just handle
> them all in {check|reset}_bandwidth() overrides.
It's ok if check_bandwidth() could get added ep and update context.

I'll spend some time to look at the code and test it.

Thank you

> 
> >
> > >
> > > +struct xhci_ep_ctx* xhci_get_ep_contex(struct xhci_hcd *xhci, struct
> > > usb_host_endpoint *ep)
> > > +{ ... }
> > > +EXPORT_SYMBOL(xhci_get_ep_context);
> > >
> > > But for v6, I'm going to submit a patch with {check|reset}_bandwidth()
> > > quirk function
> > >  switched into xhci_driver_overrides first. (and preserve existing
> > > MTK_HOST quirk functions).
> > >
> > > Thanks!
> > >
> > > > -Mathias
> > > >
> >

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