From: Felipe Balbi <balbi@ti.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Felipe Balbi <balbi@ti.com>,
Venu Byravarasu <vbyravarasu@nvidia.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"swarren@wwwdotorg.org" <swarren@wwwdotorg.org>,
"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>
Subject: Re: [PATCH v2 4/4] usb: Add APIs to access host registers from Tegra PHY
Date: Thu, 17 Jan 2013 17:32:29 +0200 [thread overview]
Message-ID: <20130117153229.GA21904@arwen.pp.htv.fi> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1301171016550.1339-100000@iolanthe.rowland.org>
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On Thu, Jan 17, 2013 at 10:21:53AM -0500, Alan Stern wrote:
> On Thu, 17 Jan 2013, Felipe Balbi wrote:
>
> > > Bits 31 & 30 from PORTSC register were allocated by our SOC designers
> > > to inform the host controller about the PHY type to be used.
> >
> > Wow, that's something you should never do. PORTSC register belongs to
> > the EHCI controller and those bits are reserved for future use and they
> > *MUST* return zero. I wouldn't be surprised if current EHCI driver
> > assumes those bits will be zero and/or makes sure they're set to zero
> > when writing to PORTSC register.
>
> In fact, those bits _have_ been assigned an official purpose in the
> EHCI-1.1 addendum. Presumably the Tegra hardware only supports
> EHCI-1.0.
I see, they're used for device addresses now.
How can we make sure on Tegra systems we won't use those top two bits ?
--
balbi
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next prev parent reply other threads:[~2013-01-17 15:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-17 8:28 [PATCH v2 4/4] usb: Add APIs to access host registers from Tegra PHY Venu Byravarasu
2013-01-17 9:02 ` Felipe Balbi
2013-01-17 12:37 ` Venu Byravarasu
2013-01-17 13:50 ` Felipe Balbi
2013-01-17 15:21 ` Alan Stern
2013-01-17 15:32 ` Felipe Balbi [this message]
2013-01-17 16:03 ` Alan Stern
2013-01-18 5:39 ` Venu Byravarasu
2013-01-17 22:18 ` Stephen Warren
2013-01-17 15:15 ` Alan Stern
2013-01-18 4:56 ` Venu Byravarasu
2013-01-18 5:42 ` Venu Byravarasu
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