Re: [PATCH] usb: ehci: make HC see up-to-date qh/qtd descriptor ASAP

From: Marc Zyngier <marc.zyngier@arm.com>
To: Stephen Warren <swarren@nvidia.com>
Cc: Russell King <linux@arm.linux.org.uk>, Greg KH <greg@kroah.com>,
	"ming.lei@canonical.com" <ming.lei@canonical.com>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
	Will Deacon <Will.Deacon@arm.com>, Marc Dietich <marvin24@gmx.de>,
	"stern@rowland.harvard.edu" <stern@rowland.harvard.edu>,
	Mark Salter <msalter@redhat.com>,
	Chen Peter-B29397 <B29397@freescale.com>,
	"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
	"linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] usb: ehci: make HC see up-to-date qh/qtd descriptor ASAP
Date: Fri, 02 Sep 2011 10:50:58 +0100	[thread overview]
Message-ID: <4E60A702.1060504@arm.com> (raw)
In-Reply-To: <74CDBE0F657A3D45AFBB94109FB122FF04B327A383@HQMAIL01.nvidia.com>

On 01/09/11 20:08, Stephen Warren wrote:
> Marc Dietich wrote at Thursday, September 01, 2011 5:14 AM:
>> I'll add Stephen Warren from NVIDIA to the CC list. He has more HW to test on.
> 
> Here are the results I found:
> 
> Harmony:
> Tegra USB3 -> SMSC9514 hub: NOT affected
> (Unplugging LAN cable, or disabling SMSC9514 LAN driver doesn't change this)
> 
> Seaboard (springbank; clamshell):
> Tegra USB1 -> no hub: Affected
> 
> Seaboard (seaboard non-clamshell):
> Tegra USB1 -> no hub: Affected
> Tegra USB3 -> no hub: Affected
> 
> TrimSlice:
> Tegra USB3 -> unknown hub: Affected
> 
> This implies there's something different about Harmony.
> 
> Is the USB hub a clue? Seaboard doesn't have one, and although I don't
> know what model TrimSlice uses, I assume it's different since I know
> TrimSlice's Ethernet is not the same as Harmony's.

Panda has the exact same USB hub configuration, and is affected. So we
can rule this out.

> I don't see anything in board-harmony.c vs. board-seaboard.c that'd affect
> anything USB-related.
> 
> Perhaps there's some kind of bootloader or BCT difference. However, my
> Harmony and both Seaboards both use (a very old) U-Boot and BCT from
> ChromeOS, so I don't imagine there's actually much difference there.

I just noticed something else. Harmony is fast *most of the time*. In
about one in 3 reboots, I get the slow behavior. When USB is fast, I
also have I2C interrupts "screaming":

 85:     294321          0       GIC  tegra-i2c
116:          0          0       GIC  tegra-i2c
118:      98542          0       GIC  tps6586x

This is a couple of seconds after boot.

When USB is slow, I see the following:
[    0.385270] tps6586x 3-0034: Chip ID read failed: -121
[    0.390584] tps6586x: probe of 3-0034 failed with error -5

... and I2C interrupt is quiet.

The I2C interrupt handler calls writel(), which does a cache sync. That
would explain the "fast" behavior of Harmony.

Do you see the same this on your board?

	M.
-- 
Jazz is not dead. It just smells funny...