linux-kernel - Re: [PATCH v6 3/4] usb: ehci: Add new EHCI driver for Broadcom STB SoC's

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Message-ID: <CAHp75VeA8JnsJgEgkv0wivinsxvk51JTVyaPhmLhsjzkqZYR8A@mail.gmail.com>
Date:   Thu, 7 May 2020 00:01:16 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Alan Cooper <alcooperx@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        ": Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        DTML <devicetree@...r.kernel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        USB list <linux-usb@...r.kernel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v6 3/4] usb: ehci: Add new EHCI driver for Broadcom STB SoC's

On Wed, May 6, 2020 at 11:23 PM Alan Cooper <alcooperx@...il.com> wrote:
> On Tue, May 5, 2020 at 7:00 AM Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> > On Thu, Apr 30, 2020 at 07:12:57AM -0400, Al Cooper wrote:

...

> > > +     /* Hook the hub control routine to work around a bug */
> >
> > What bug?  This feels wrong.
>
> The bug is explained in a comment above the ehci_brcm_hub_control()
> routine as follows:
> /*
>  * ehci_brcm_hub_control
>  * Intercept echi-hcd request to complete RESUME and align it to the start
>  * of the next microframe.
>  * If RESUME is complete too late in the microframe, host controller
>  * detects babble on suspended port and resets the port afterwards.
>  * This s/w workaround allows to avoid this problem.
>  * See SWLINUX-1909 for more details
>  */
> I'll remove the internal bug tracking reference from the comment.

I guess you may leave the internal bug reference. I can tell from my
experience that's hard to understand what was going on in the driver
in years perspective. It will help whoever in this company have a
chance to look after the driver.

-- 
With Best Regards,
Andy Shevchenko