ColdFire/68K Microcontrollers and ProcessorsのトピックRe: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

jkimble — Tue, 18 Nov 2008 09:47:45 GMT

I've been working with a frame buffer driver for this board for several weeks now and, after a lot of checking and rechecking, I find that calls to mmap with my pointer to /dev/fb0 returns an invalid (gdb reports "out of bounds") address. Direct ioctl calls work and calls from within the frame buffer driver work too. Only user space programs that use mmap (like nano-X...) fail and they always fail with a seg fault upon trying to write to the address returned by mmap.

I'm looking over /drivers/video/fbmem.c now and comparing it to the 2.6.10 version. Somethings obviously not right though...

Anyone have any experience with this? I'd be happy to show my examples.

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

Nabendu — Wed, 19 Nov 2008 04:09:23 GMT

I am facing sameproblem here..Seems that mmap for 2.6.25 kernel sm712 frame buffer is not working.

Yes I also found nanox like program cant access the mmaped address.Whenever It tries to access the address got from mmap it gives segmentation fault.

I am also going through sm712fb code no success yet..

Was it working on 2.6.10 kernel?
Any solution found??

Regards,
Nabendu

Message Edited by Nabendu on 2008-11-19 02:04 AM

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

jkimble — Wed, 19 Nov 2008 04:44:17 GMT

OK. That confirms it then. I wasn't 100% sure but it seemed like the only thing going wrong (mmap).

There was no frame buffer driver for the chip I was using in the 2.6.10 kernel. Epson had (again) an example driver for other chips in the same family for the 2.6.8 kernel. I ported it to my chip and the 2.6.10 kernel. It's worked very well for 2.6.10. I've got a fairly sophisticated GUI running on Nano-X and with a touchscreen. Very nice.

Now I want to go to 2.6.25 but, though I'm 98% sure of my driver, no user space programs can use it. The mmap call definately sends back and invalid address. I'm in the process now of looking into what it's doing. Never been in this part of the kernel before. Really don't want to hack it up and make things worse. I'm not getting any other suggestions though.

I'll post here if I can work it out in a reasonable way.

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

Nabendu — Wed, 19 Nov 2008 15:39:47 GMT

btw which version of gdb you are using? The default gdb given within ltib iso image?

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

jkimble — Wed, 19 Nov 2008 23:08:08 GMT

Yes, the gdb that came with the 2.6.25 kernel. I just compiled in the package and it seems to work well.

I'm a little suprised that some Freescaler hasn't spoken up here. As an embedded OS being able to write drivers is a crucial thing. This will have to be fixed if this kernel is going to be used for anything beyond messing around. I'm at point where I must make a decision this week whether to continue a product release with the 2.6.10 kernel (which is missing some things I'd really like to have) or find a solution to the mmap issue. It's really NOT a production kernel if mmap fails and it gives me grave concerns for the rest of the memory management in this release. I feel like I can't trust it..

Any Freescaler familiar with this kernel, I'd REALLY apprciate some feed back.

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

Nabendu — Wed, 19 Nov 2008 23:38:13 GMT

Yes ,it is unfortunate they don't reply.I also raised a service request but they dont answer.

I think i found some solution..

I found that I can read mmaped area but fail in write only.

There is a write protection bit in MMU for page handling in m5475,it should be on for write permission.
Enabled by CF_PAGE_WRITABLE mask.

So added folowing over vma,
pgprot_val(vma->vm_page_prot) = CF_PAGE_NOCACHE | (pgprot_val(vma->vm_page_prot) & ~CF_PAGE_COPYBACK);
if(vma->vm_flags & VM_WRITE)
pgprot_val(vma->vm_page_prot) |= CF_PAGE_WRITABLE;

in fb_pgprotect macro..

It should work now.Tomorrow I will check on my board.

If it doesn't work, there must be some serious problem on paging or elsewhere.

--------------------------------------
For my case gdb with 2.6.25 giving compilation error...I can't include gdb using ltib. Can you send me your working gdb spec file?

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

jkimble — Wed, 19 Nov 2008 23:41:18 GMT

Ha! That's funny. I was just looking at that macro and wondering if I should change it. I'll give your fix a try. I agree with your analysis. Let's hope that's all it is....

I'll let you know what I find.

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

JimDon — Thu, 20 Nov 2008 00:00:59 GMT

Nabendu wrote:
Yes ,it is unfortunate they don't reply.I also raised a service request but they dont answer.

My experience had been that they will reply when the have an answer (i.e. fix). Chances are they were able to reproduce, or the would have asked for more info right away.

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

jkimble — Thu, 20 Nov 2008 00:04:28 GMT

Oh sure. I'm not whacking on them. They've done a great job of support in the past. If it were a trivial thing I'm sure they'd have had an answer right away.

It's just a frustrating problem...

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

kmahan — Thu, 20 Nov 2008 00:14:12 GMT

I've got the service ticket. I've just got a number of other projects going on currently. Not enough time in the day!

I did reply on a different thread, and it appears that Nabendu figured out what I was talking about.

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

Nabendu — Thu, 20 Nov 2008 01:24:08 GMT

Cool up guys...no blame game.The type of work they doing are great.& I understand they may be busy...

We need the solution..

If we try and make a solution that will be good( may be for gpp package)

Cheers..

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

jkimble — Thu, 20 Nov 2008 01:43:15 GMT

Yes the mod Nabendu listed earlier seemed to correct the problem I was having with my frame buffer. Not sure if that fixes the root of the problem but at first glance I think it might be all that's required.

Happy days!

Thanks!

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

aeg — Thu, 20 Nov 2008 13:06:52 GMT

Hi guys,

glad you found a fix for the frame buffer issue. I found the same thing a while back and have a service request with Freescale. I'll test Nabendu's mod tomorrow.

The weird thing is that mmaping via uio seems to work fine. That's how I wrote my nano-x driver.

Best,
Andreas

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

Nabendu — Thu, 20 Nov 2008 22:24:59 GMT

The fix is not working.

pgprot_val(vma->vm_page_prot)= 1c10
after MMU write protection off.
pgprot_val(vma->vm_page_prot)= 1c98 .

checking further ..

Any one let me know about 2.6.10 kernel vma->vm_page_prot valus....

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

jkimble — Sat, 22 Nov 2008 04:37:46 GMT

I confirm seeing the same vma->vm_page_prot values of 0x1c10 before the call tofb_pgprotect () and 0x1c98 after on the 2.6.25 kernel. Oddly this seems to fix my issue for nano-X. Another frame buffer application, however, continues to have a seg fault problem.

I have this all working on the 2.6.10 kernel. The values before and after for that kernel were:

Before fb_pgprotect (Equivalent section in fbmem() ) - 0x1c19
After fb_pgprotect (Equivalent section in fbmem() ) - 0x1c99

Please let me know if you find anything new on this. I will do the same.

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

Nabendu — Sat, 22 Nov 2008 06:51:58 GMT

if your printks are like below....
print .. pgprot_val(vma->vm_page_prot)
pgprot_val(vma->vm_page_prot) = CF_PAGE_NOCACHE | (pgprot_val(vma->vm_page_prot) & ~CF_PAGE_COPYBACK);
       if(vma->vm_flags & VM_WRITE)
           pgprot_val(vma->vm_page_prot) |= CF_PAGE_WRITABLE;
           vma->vm_flags &= ~0x00004000;       // to be checked
   print pgprot_val(vma->vm_page_prot)

Then vma->prot = 0x1c19= (CF_PAGE_ACCESSED|CF_PAGE_VALID|CF_PAGE_SHARED|CF_PAGE_READABLE|CF_PAGE_WRITABLE|CF_PAGE_DIRTY)

Then vma->prot = 0x1c99= (CF_PAGE_ACCESSED| CF_PAGE_VALID | CF_PAGE_SHARED | CF_PAGE_READABLE | CF_PAGE_NOCACHE | CF_PAGE_WRITABLE | CF_PAGE_DIRTY)

As far I know the first value provided vma created by mmap...

But for 2.6.25,    0x1c10 =
(CF_PAGE_ACCESSED | CF_PAGE_VALID | CF_PAGE_SHARED | CF_PAGE_READABLE)

dirty page bit may be ok, but dont know whether WRITE permission should be on or not.

I am not sure wheather io_remap_pfn_range routine work on MMU on the rWR permissins bits/ it is already used in between user level mmap and fb_mmap calls ( i mean the vma operation)

Any freescaler / experienced freescale mmap system call probly can answer.

I am planning to chechk it by writting a simple mmap device driver and check wheter i can write it or not.I think it will also fail.(worst part is to look mm system codes) .

jkimble can you provide me the "vma->vm_page_prot" valueafter remap_pfn_range?

Message Edited by Nabendu on 2008-11-22 04:25 AM

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

Nabendu — Sat, 22 Nov 2008 06:59:38 GMT

I am just wondering only few peoples tried microwindow on 5475evb on 2.6.25 and got this problem ?

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

Nabendu — Tue, 25 Nov 2008 18:41:26 GMT

Message Edited by Nabendu on 2008-11-25 04:12 PM

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

jkimble — Tue, 25 Nov 2008 21:50:55 GMT

That's fantastic! Thanks for finding that!

Did you need to retain the change to fb_pgprotect() ? I'm assuming you do since we're really just going back to the 2.6.10 settings.

Thanks again!

Re: MCF5485EVB, Linux 2.6.25 kernel: MMap broken...

Nabendu — Tue, 25 Nov 2008 22:12:49 GMT

you are welcome..

i need to know in old configuration(2.6.10) what mouse you were using? is it usb mouse/touchscreen ?
In my case usb mouse (is it psaux?) is not working.

and what keyboard you were using.

I had not tested after removing the changes in fb_protect but i think without the change it should also work..

Message Edited by Nabendu on 2008-11-25 07:46 PM