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

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Message-ID: <CAATdQgD2OAmf7_NWSVwzyJE7mF0vngzE=QeE79PS7MJsgPhbtA@mail.gmail.com>
Date:   Tue, 12 Jan 2021 13:48:39 +0800
From:   Ikjoon Jang <ikjn@...omium.org>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc:     Chunfeng Yun <chunfeng.yun@...iatek.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, 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:

+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
>