linux-kernel - Re: [PATCH v5] usb: xhci-mtk: fix unreleased bandwidth data

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Message-ID: <1610612988.30053.15.camel@mhfsdcap03>
Date:   Thu, 14 Jan 2021 16:29:48 +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

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().

> 
> +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
> >