linux-kernel - Re: [PATCH v2] USB: ehci-s5p: Fix phy reset

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Date:	Thu, 14 Mar 2013 08:31:20 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Thomas Abraham <thomas.abraham@...aro.org>
Cc:	Alexander Graf <agraf@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-usb@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	dmueller@...e.de, Vivek Gautam <gautam.vivek@...sung.com>,
	Jingoo Han <jg1.han@...sung.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Vincent Palatin <vpalatin@...omium.org>, jwerner@...omium.org
Subject: Re: [PATCH v2] USB: ehci-s5p: Fix phy reset

Hi,

On Thu, Mar 14, 2013 at 7:58 AM, Thomas Abraham
<thomas.abraham@...aro.org> wrote:
>> I can see your point, but as I mentioned earlier there seems to be some timing issue here. By simply doing the reset a few ms earlier (in the first probe, before the driver detects that it needs to defer probing), I already can't find the hub on the bus later.
>>
>> So I'm assuming that the same thing would also happen if I put it even earlier in machine init.
>
> True, I missed that point. The usb hub connected over hsic interface,
> after power-on-reset, might have initiated the 'connect' state on
> seeing the idle condition on the bus and since the host/phy controller
> is not ready yet, the connect might have failed.
>
> So the correct sequence would be, after the usb host controller and
> the phy controllers are initialized, the 'reset' pin on the on-board
> usb hub should be asserted. Upon releasing that reset, the usb hub
> would initiate the 'connect' state on the HSIC bus.

I think we ran into similar issues on one of our boards that had a hub
attached to the HSIC port.  We had to make our fix in a version of the
code that's nowhere near what landed upstream (so our change is not
relevant), but we're definitely interested in whatever solution you
come up with.  :)

-Doug
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