From: marek.vasut@gmail•com (Marek Vasut)
To: linux-arm-kernel@lists•infradead.org
Subject: PXA270 Random Hangs at Low Core Freq
Date: Mon, 25 Oct 2010 21:46:05 +0200 [thread overview]
Message-ID: <201010252146.05874.marek.vasut@gmail.com> (raw)
In-Reply-To: <A257B8DC-1E93-4888-AA57-AB9A41AF11AA@prograde.net>
On Monday 25 October 2010 21:02:42 Michael Cashwell wrote:
> On Oct 22, 2010, at 4:41 AM, Haojian Zhuang wrote:
> > On Fri, Oct 22, 2010 at 8:22 AM, Marek Vasut <marek.vasut@gmail•com> wrote:
> >> Dne Po 18. ??jna 2010 19:38:49 Michael Cashwell napsal(a):
> >>> I've been fighting inexplicable hangs on two different PXA270 designs
> >>> running various kernels since early 2.6.28.x. The first board was
> >>> custom (and of dubious integrity) but I'm currently seeing it on
> >>> Gumstix Verdex PROs running 2.6.35.7.
> >>
> >> Could it be memory-related ? Like, RAM crashes because of refresh speed
> >> or something?
>
> I wondered about this myself, especially on the custom board and u-boot.
> That's why I hadn't turned to the community until I was on unmodified
> commercial hardware.
>
> What I'd like to test would be a Gumstix-supplied uboot and current Linux
> with CPUfreq disabled. That would eliminate all the CPUfreq code and its
> plethora of errata from consideration. The problem is that such a setup
> runs at a fixed *high* CPU core frequency. I've never seen that hang.
>
> The best I've been able to do is two alternate cases (stock high-freq
> u-boot + a current Linux with CPUfreq enabled so that it lowers the speed;
> and my custom u-boot that runs only at low speed + a current Linux with
> CPUfreq disabled so linux just uses what u-boot sets). Both of these hang
> as described.
>
> Meaningfully rolling back to the Gumstix's vendor-supplied Linux distro is
> more difficult. It's running a 3+ year old 2.6.21 kernel variant that
> lacks support for recent MTD FLASH parts and features like UBIFS. I used
> that version on an OMAP and recall its MMC support was rather sketchy and
> since writing to a uSD card is my test case I'm somewhat doubtful that the
> results from such testing would mean much.
>
> Lastly, I've run Charles Cazabon's memtester (c. 2006 v 4.0.6) over 99% of
> the free SDRAM for days at a time and have seen no problems at all. If it
> were an outright SDRAM init/timing/refresh issue I'd expect something that
> strenuous to report an error.
>
> > Suggest to check errata first. Maybe we need some special code sequence.
>
> I agree that it has the feel of a CPU errata. (What else would hang the
> core so badly that JTAG would disconnect?) So I've re-read the Rev E
> (April 3rd 2009) errata docs from Marvell from start to finish but nothing
> jumps out at me. The problem is not knowing where to focus. Having
> eliminated the CPU-freq code itself (which relies on CPU features with
> many errata) I'm left rather empty handed.
>
I think I noticed something similar running ZipitZ2 on 312MHz ... yet I was
unable to figure out the problem as well ...
> My only idea is that some kernel code path (likely interacting with an
> integrated peripheral) is too slow at low core frequencies and is either
> violating the hardware spec outright or is hitting an errata.
>
> My testing to date (and that I'm on commercial hardware) makes me think
> that others should be seeing the same problem. It won't occur
> out-of-the-box because normally people want highest performance (high core
> CPU frequencies). With the default u-boot and without CPU-freq to lower it
> the hang doesn't happen.
>
> But perhaps someone has prioritized power savings as I'm trying to do and
> then they should see it.
>
> -Mike
next prev parent reply other threads:[~2010-10-25 19:46 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-18 17:38 PXA270 Random Hangs at Low Core Freq Michael Cashwell
2010-10-22 0:22 ` Marek Vasut
2010-10-22 8:41 ` Haojian Zhuang
2010-10-25 19:02 ` Michael Cashwell
2010-10-25 19:22 ` Eric Miao
2010-10-26 0:05 ` Haojian Zhuang
2010-10-26 17:06 ` Michael Cashwell
2011-02-03 12:04 ` Vasily Khoruzhick
2011-02-03 12:52 ` Michael Cashwell
2011-03-04 16:16 ` Vasily Khoruzhick
2011-03-04 18:42 ` Michael Cashwell
2011-03-04 18:51 ` Vasily Khoruzhick
2011-03-30 11:45 ` Michael Cashwell
2010-11-10 13:54 ` Pavel Machek
2010-10-25 19:46 ` Marek Vasut [this message]
2010-10-25 20:53 ` Michael Cashwell
2010-10-26 14:47 ` Marek Vasut
2010-12-03 20:20 ` Robert Jarzmik
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