Re: Seg fault on any FB write (Epson S1D13A04onColdfire running 2.6.25)

[Kristoffer Ericson <kristoffer.ericson@gmail.com>]

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On Thu, 13 Nov 2008 09:50:50 +0100
Hinko Kocevar <hinko.kocevar@cetrtapot.si> wrote:

> James Kimble wrote:
> > 
> > In looking at your driver (which I think is a lot better organized than
> > the general one that came with the kernel by the way) I see that you're
> > doing a whole string of:
> > 
> >                                            ~~~~~~~~~~
> >    device_create_file(&s1d13706fb_device.dev, &dev_attr_reg_0x12);
> >    device_create_file(&s1d13706fb_device.dev, &dev_attr_reg_0x14);
> >    device_create_file(&s1d13706fb_device.dev, &dev_attr_reg_0x16);
> >                                             ~~~~~~~~~~     
> > In  s1d13706fb_init(). I didn't do any of this my driver. Is this needed
> > for any purpose other than to allow easy access to change the values in
> > these registers in user space?
> > 
> 
> It is there purely for debugging purposes. It also allows quick setup of
> eg. different LCD panels that require some tweaking in order to center the
> image or fix refresh rate.
> 
> > I was able to port your driver to the values and registers used by my
> > device and the behavior is virtually the same as with my driver. Screen
> > is initialized, I can see the color palette get set and the panel
> 
> And if you draw a pixel from the driver - does it work? Another quick test
> is to set color palette and then memset() complete framebuffer memory to
> a singles value stored in palette, or change the palette index value to
> achieve image color change on the screen.
> 
> > enable. Everything boots up fine but none of my user space applications
> > work. The first time I try to write to a register or video memory I get
> > a seg fault.
> > 
> 
> Does the oops appear in the dmesg, too?
> 
> > This has got to be some kind of memory configuration issue. I've moved
> > the CS configuration for this device to different memory locations but
> > it doesn't change the behavior. I'm setting things up in U-Boot in
> > exactly the same way I had been setting them up in Colilo for the 2.6.10
> > kernel (where everything worked).
> > 

I agree, it sounds alot more like a deeper bug
than restricted to your video driver. I can't see
anything that would cause that (atleast yet). Would
be worth it to get some input from linux-m68k (coldfire m68k right?).

> 
> What about other memory mapped devices you might have on the system? Do
> they function properly? If not this might be indicator where look for
> the problem.
> 
> Regards,
> Hinko
> 
> -- 
> Hinko Kočevar, OSS developer
> ČETRTA POT, d.o.o.
> Planina 3, 4000 Kranj, SI EU
> tel     ++386 (0) 4 280 66 03
> e-mail  hinko.kocevar@cetrtapot.si
> http    www.cetrtapot.si
> 
> 
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-- 
Kristoffer Ericson <kristoffer.ericson@gmail.com>

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