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

From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Cooper <alcooperx@gmail.com>,
	": Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	BCM Kernel Feedback <bcm-kernel-feedback-list@broadcom.com>,
	DTML <devicetree@vger.kernel.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	USB list <linux-usb@vger.kernel.org>,
	Mathias Nyman <mathias.nyman@intel.com>,
	Rob Herring <robh+dt@kernel.org>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: Re: [PATCH v6 3/4] usb: ehci: Add new EHCI driver for Broadcom STB SoC's
Date: Thu, 7 May 2020 12:06:24 +0300	[thread overview]
Message-ID: <CAHp75Vdok4WxH9b2q1GK7W_mcmNW-OuReC0y1wLQH9YLYqupmg@mail.gmail.com> (raw)
In-Reply-To: <20200507064145.GB777100@kroah.com>

On Thu, May 7, 2020 at 9:41 AM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> On Thu, May 07, 2020 at 12:01:16AM +0300, Andy Shevchenko wrote:
> > On Wed, May 6, 2020 at 11:23 PM Alan Cooper <alcooperx@gmail.com> wrote:
> > > On Tue, May 5, 2020 at 7:00 AM Greg Kroah-Hartman
> > > <gregkh@linuxfoundation.org> 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.
>
> "internal bug references" mean nothing to the 99% of the people that can
> see this.  Document the heck out of what this is instead please.

As far as I understand the bug is being described in the same file
somewhere else, that's why internal reference *on top of explanation*
would be valid.

-- 
With Best Regards,
Andy Shevchenko