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From: Alan Stern <stern@rowland.harvard.edu>
To: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Emilio Lopez <emilio@elopez.com.ar>,
	Mike Turquette <mturquette@linaro.org>, <kishon@ti.com>,
	<hdegoede@redhat.com>, Boris Brezillon <boris@free-electrons.com>,
	<linux-kernel@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-usb@vger.kernel.org>, <kevin.z.m.zh@gmail.com>,
	<sunny@allwinnertech.com>, <shuge@allwinnertech.com>,
	<zhuzhenhua@allwinnertech.com>, <linux-sunxi@googlegroups.com>,
	Boris BREZILLON <boris.brezillon@free-electrons.com>
Subject: Re: [PATCH 4/7] usb: ehci-platform: add optional reset controller retrieval
Date: Wed, 7 May 2014 10:25:55 -0400 (EDT)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1405071020490.1325-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <1399434623-20383-5-git-send-email-maxime.ripard@free-electrons.com>

On Tue, 6 May 2014, Maxime Ripard wrote:

> From: Boris BREZILLON <boris.brezillon@free-electrons.com>
> 
> On the Allwinner's A31 SoC the reset line connected to the EHCI IP has to
> be deasserted for the EHCI block to be usable.
> 
> Add support for an optional reset controller that will be deasserted on
> power off and asserted on power on.
> 
> Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Is this really a _reset_ line?  That is, when you assert the reset 
line, does it actually reset the EHCI controller, or does it merely 
leave the controller in a partially powered-down state?

The difference is important.  During suspend, the controller is
supposed to remember the state of the port connections as well as other
settings.  If it doesn't, the controller and all attached USB devices
will have to be reinitialized every time the controller resumes, which
will increase the latency.

Alan Stern


WARNING: multiple messages have this Message-ID (diff)
From: stern@rowland.harvard.edu (Alan Stern)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 4/7] usb: ehci-platform: add optional reset controller retrieval
Date: Wed, 7 May 2014 10:25:55 -0400 (EDT)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1405071020490.1325-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <1399434623-20383-5-git-send-email-maxime.ripard@free-electrons.com>

On Tue, 6 May 2014, Maxime Ripard wrote:

> From: Boris BREZILLON <boris.brezillon@free-electrons.com>
> 
> On the Allwinner's A31 SoC the reset line connected to the EHCI IP has to
> be deasserted for the EHCI block to be usable.
> 
> Add support for an optional reset controller that will be deasserted on
> power off and asserted on power on.
> 
> Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Is this really a _reset_ line?  That is, when you assert the reset 
line, does it actually reset the EHCI controller, or does it merely 
leave the controller in a partially powered-down state?

The difference is important.  During suspend, the controller is
supposed to remember the state of the port connections as well as other
settings.  If it doesn't, the controller and all attached USB devices
will have to be reinitialized every time the controller resumes, which
will increase the latency.

Alan Stern

  reply	other threads:[~2014-05-07 14:25 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-07  3:50 [PATCH 0/7] Add Allwinner A31 USB support Maxime Ripard
2014-05-07  3:50 ` Maxime Ripard
2014-05-07  3:50 ` [PATCH 1/7] clk: sunxi: Implement A31 USB clock Maxime Ripard
2014-05-07  3:50   ` Maxime Ripard
2014-05-07  3:50 ` [PATCH 2/7] ARM: sun6i: Add the USB clocks to the DTSI Maxime Ripard
2014-05-07  3:50   ` Maxime Ripard
2014-05-07  3:50 ` [PATCH 3/7] phy: usb: sunxi: Introduce Allwinner A31 USB PHY support Maxime Ripard
2014-05-07  3:50   ` Maxime Ripard
2014-05-07 13:35   ` Kishon Vijay Abraham I
2014-05-07 13:35     ` Kishon Vijay Abraham I
2014-05-07 21:57     ` Maxime Ripard
2014-05-07 21:57       ` Maxime Ripard
2014-05-07  3:50 ` [PATCH 4/7] usb: ehci-platform: add optional reset controller retrieval Maxime Ripard
2014-05-07  3:50   ` Maxime Ripard
2014-05-07 14:25   ` Alan Stern [this message]
2014-05-07 14:25     ` Alan Stern
2014-05-07 22:00     ` Maxime Ripard
2014-05-07 22:00       ` Maxime Ripard
2014-05-08  7:29       ` Hans de Goede
2014-05-08  7:29         ` Hans de Goede
2014-05-08 14:07         ` Alan Stern
2014-05-08 14:07           ` Alan Stern
2014-05-10  1:17           ` Maxime Ripard
2014-05-10  1:17             ` Maxime Ripard
2014-05-07  3:50 ` [PATCH 5/7] usb: ohci-platform: Enable optional use of reset controller Maxime Ripard
2014-05-07  3:50   ` Maxime Ripard
2014-05-07 16:26   ` Sergei Shtylyov
2014-05-07 16:26     ` Sergei Shtylyov
2014-05-07 22:03     ` Maxime Ripard
2014-05-07 22:03       ` Maxime Ripard
2014-05-08 13:11       ` Sergei Shtylyov
2014-05-08 13:11         ` Sergei Shtylyov
2014-05-07  3:50 ` [PATCH 6/7] ARM: sun6i: dt: Add support for the USB controllers Maxime Ripard
2014-05-07  3:50   ` Maxime Ripard
2014-05-07  3:50 ` [PATCH 7/7] ARM: sunxi: dt: add APP4-EVB1 board support Maxime Ripard
2014-05-07  3:50   ` Maxime Ripard
2014-05-07  5:10   ` [linux-sunxi] " Koen Kooi
2014-05-07  5:10     ` Koen Kooi
2014-05-07  6:46     ` Hans de Goede
2014-05-07  6:46       ` Hans de Goede
2014-05-07  8:25 ` [PATCH 0/7] Add Allwinner A31 USB support Hans de Goede
2014-05-07  8:25   ` Hans de Goede

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