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Re: ARM kernel cross compilation issues for iMX53


I've had my iMX53 Quick Start for a few days now and I've been spending my time getting a basic stable Debian configuration on it.  I hope you don't mind me asking a few questions about the configuration you documented at: http://eewiki.net/display/linuxonarm/i.MX53+Quick+Start

At this point, I'm building your kernel and what I believe is called the 2.6.35_11.01.00 kernel included with the Freescale BSP and LTIB utility for the i.MX53 Quick Start.  I'm trying to understand the differences between the two so I can learn by comparing and contrasting.

One of the first problems I ran into is that I can't build a working u-boot using LTIB.  Included with the BSP is a prebuilt u-boot.bin file that does work, but there isn't documentation as to where it came from or any suggestion why the u-boot.bin I build with LTIB is different than the pre-built one supplied with the BSP.  Following your instructions, I can easily build a more modern, version of u-boot which works great.  However, seems have some known incompatibilities regarding how the UARTs are clocked with older kernels.  Until I can figure out how to correct this, I get garbage out the serial port when booting other kernels as Linux switches to using its tty serial drivers about half-way through the boot.  I notice you have a local patch tweaking the UART clock and I'll see if I can work that back into the other kernels.

Anyway, the question I have for you is where does your kernel come from?  It seems to come directly from the mailine kernel at kernel.org using the following URL:


This would seem to imply that it's missing most, if not all, the dozens of kernel patches that Freescale applies to the same version of the kernel built with LTIB.  Is this a correct assumption on my part?  Or, have the Freescale patches made it into the mainline Linux kernel?  Also, how are you specifically requesting the branch of the kernel?  Unfortunately, I'm still pretty ignorant of how git works and I don't see how this is done.

I can successfully boot your kernel, but message 'usb wakeup is here' is output on the serial console every two seconds or so which makes doing anything very painful.  I don't know how to turn this off and I presume it's related to something you mentioned about usb support not being fully supported in the mainline kernel yet for the iMX53.  I guess I need to tweak the configuration settings in the kernel to see if I can silence this message.

Finally, I'm wondering if you can comment on the stability of the kernel built by your instructions.  Is still very much a work in progress, or is it working for you well enough to other aspects of porting Debian to the iMX53.  I suspect it's still a work in progress, but perhaps I'm just doing some things wrong.

Thanks again for your help and any additional comments you can provide.

Mike Thompson

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