James Kimble

seg fault problem with MCF5485EVB running recently released 2.6.25 Linux kernel

Discussion created by James Kimble on Nov 13, 2008
Latest reply on Nov 17, 2008 by James Kimble
I'm running the latest kernel released (2.6.25) on a board that is a mod of the MCF5485EVB board (more flash and more RAM) with an Epson (S1D13A04) video chip. I had this hardware working (nano-X GUI with touchscreen, the works) with the old kernel release (2.6.10) and though the drivers for the two kernels are different they're not that different.

The driver for the device loads, the screen is initialized (I've even been able to have a logo drawn on the screen from the driver) and the frame buffer device (fb0) can be opened. However any attempt to write to a device register or the devices video memory results in a seg fault. For about a week I've been going round and round looking at the driver and trying to see where I'm going wrong. Even to the extent of going to the Linux frame buffer news group and getting some expert input.

What I see is that I can work with the registers and video memory from kernel space with no problem. However when I open the device file to work in user space writing to the device results in a seg fault. Can anyone knowledgeable about how the new kernel handles memory think of a reason that the new kernel might show this behaviour where the old kernel didn't? This is the same hardward and the same user space applications. The driver is slightly different but not by much.

I've been hung on this for days and it makes no sense to me. I've tried moving the memory around (setting the CS to another address in U-Boot) but it makes no difference in the behaviour.

I'd REALLY appreciate ANY ideas or thoughts.




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