linux-kernel - Re: [RFC PATCH] usb: dwc2: host: Rewrite the microframe scheduler

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Message-ID: <CAD=FV=VrcimjU8aeFemRQ9cO79XsoacHAzmHWRJN6nZtnipfDA@mail.gmail.com>
Date:	Mon, 9 Nov 2015 11:24:00 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	John Youn <John.Youn@...opsys.com>, Felipe Balbi <balbi@...com>
Cc:	Yunzhi Li <lyz@...k-chips.com>,
	Heiko Stübner <heiko@...ech.de>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Julius Werner <jwerner@...omium.org>,
	"Herrero, Gregory" <gregory.herrero@...el.com>,
	"Kaukab, Yousaf" <yousaf.kaukab@...el.com>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Ming Lei <ming.lei@...onical.com>,
	Douglas Anderson <dianders@...omium.org>,
	John Youn <johnyoun@...opsys.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] usb: dwc2: host: Rewrite the microframe scheduler

Hi,

On Fri, Nov 6, 2015 at 5:50 PM, Douglas Anderson <dianders@...omium.org> wrote:
> The old microframe scheduler was terribly hard to follow and (it seemed
> to me) that it had some bugs in it.
>
> Let's re-write it in a simpler, easier-to-read way.  Hopefully this will
> work better.
>
> Note: no known problems are fixed by this patch, and in fact I can see
> very little impact of the microframe scheduler overall.
>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>  drivers/usb/dwc2/hcd_queue.c | 72 ++++++++++++++++++++------------------------
>  1 file changed, 32 insertions(+), 40 deletions(-)

Self-NAKing this change.

I wrote up some test code to help visualize how things were scheduled.
That proved that the old function is pretty broken, but the new
function not only has a typo (using "i" instead of "j" in a few
places) but also suffers from some of the same problems as the old
function.

It might be easy to use the bitmap functions to implement this easily
/ properly.  I'll see if I can do that.

-Doug
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