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Message-ID: <m339shmhag.fsf@pullcord.laptop.org> Date: Fri, 08 Oct 2010 00:37:11 -0400 From: Chris Ball <cjb@...top.org> To: Man Spaz <man.spaz@...il.com> Cc: linux-kernel@...r.kernel.org Subject: Re: Tips on debugging suspend/resume failure Hi, > But the question remains, how to get debug out? Is there a dmesg > buffer that can persist if DRAM is being refreshed perhaps? The most promising attempts involve using GPU RAM to store dmesg, since it persists across a soft reboot and isn't going to be overwritten as long as you get to it before the video driver does after the crash. (Which you can ensure by blacklisting the driver.) > Is there another way to skin this mongrel, I mean cat? The most basic tool is probably CONFIG_PM_TRACE, which uses the real-time clock to store a signature for the last driver to init during suspend/resume -- after the crash, the kernel will interpret the RTC hash it placed to give you a hint as to what might be failing. The real answer, though, is to just keep trying to find any way at all to get usable serial output, including by finding a different machine with the same problem that has a serial port. - Chris. -- Chris Ball <cjb@...top.org> <http://printf.net/> One Laptop Per Child -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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