linux-kernel - Re: [PATCH v3 1/2] usb: host: ehci-tegra: Grab the correct UTMI pads reset

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Message-ID: <20160504145710.GA14708@kroah.com>
Date:	Wed, 4 May 2016 07:57:10 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Stephen Warren <swarren@...dotorg.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Jon Hunter <jonathanh@...dia.com>, linux-usb@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] usb: host: ehci-tegra: Grab the correct UTMI pads
 reset

On Wed, May 04, 2016 at 04:39:59PM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
> 
> There are three EHCI controllers on Tegra SoCs, each with its own reset
> line. However, the first controller contains a set of UTMI configuration
> registers that are shared with its siblings. These registers will only
> be reset as part of the first controller's reset. For proper operation
> it must be ensured that the UTMI configuration registers are reset
> before any of the EHCI controllers are enabled, irrespective of the
> probe order.
> 
> Commit a47cc24cd1e5 ("USB: EHCI: tegra: Fix probe order issue leading to
> broken USB") introduced code that ensures the first controller is always
> reset before setting up any of the controllers, and is never again reset
> afterwards.
> 
> This code, however, grabs the wrong reset. Each EHCI controller has two
> reset controls attached: 1) the USB controller reset and 2) the UTMI
> pads reset (really the first controller's reset). In order to reset the
> UTMI pads registers the code must grab the second reset, but instead it
> grabbing the first.
> 
> Signed-off-by: Thierry Reding <treding@...dia.com>

Any reason you don't want this backported to stable kernels?