RE: [Ltib] Framebuffer problem with ltib-cf_nommu-20081215

[Robert S. Grimes]

Hi Tony,

Yes, I agree that it sounds like a hardware/driver discrepancy (nice choice of words there!).  The board is indeed custom, but heavily based on the Freescale/LogicPD design, especially in the LCD and touchscreen areas.

Thanks for the pointers regarding the timing parameters.  I don't know anything about the details - I was hoping the driver would "just work" ;-) - but it seems it's time to get my hands a little dirty...

Take care,
-Bob

---- Original message ----
> Date: Thu, 30 Apr 2009 07:27:21 -0700
> From: "Anthony L. Montiel" <address@hidden>
> Subject: RE: [Ltib] Framebuffer problem with ltib-cf_nommu-20081215
> To: <address@hidden>
> >Hi Robert,
> >
> >I've done some Framebuffer work - so I thought I'd give you my 2 cents.
> >However, I don't know anything about the mcf5329, so caveat-emptor...
> >
> >The description of "shearing" stands out for me - I've seen that happen
> >in a number of different circumstances:
> >- I assume the embedded system isn't "loaded" very heavily - that can
> >  sometimes cause "shearing" or "tearing"
> >- Because you are running at a low resolution, most performance related
> >  issues can be ignored
> >
> >Unfortunately, this leads me to think that there might be a discrepancy
> >between the driver and the hardware. There are a number of timing
> >parameters which might lead to this problem. I am assuming you are
> >running on custom hardware - not a reference design/Freescale dev system?
> >
> >If this is the case, the good news is that it is easy to update the 
> >timing values for the driver. Again, I'm not sure if it holds for the
> >mcf5329, but for the i.MX the file to look at is:
> >   .../linux/drivers/video/mxc/mxcfb_modedb.c
> >
> >I hope this helps in some small way...Regards,
> >Tony
> >
> >-----Original Message-----
> >From: address@hidden
> >[mailto:address@hidden On Behalf Of
> >Stuart Hughes
> >Sent: Thursday, April 30, 2009 2:04 AM
> >To: address@hidden
> >Cc: address@hidden
> >Subject: Re: [Ltib] Framebuffer problem with ltib-cf_nommu-20081215
> >
> >Hi Robert,
> >
> >Have you tried running this test code on a PC (x86).  It it works on 
> >that as expected it would tend to imply there may be a problem with the 
> >hardware or driver for the mcf5329.  Once you've established that it's 
> >probably worth contacting Freescale as they'd have a platform to test 
> >on.  I'd be interested to hear what you find out.
> >
> >Also once resolved, if you're willing we could put your updated kernel 
> >on the the public Savannah site.
> >
> >Regards, Stuart
> >
> >Robert S. Grimes wrote:
> >> I've been trying to get Microwindows/Nano-X to work with the BSP from
> >> Freescale, which features a kernel a bit newer than CVS for the mcf5329
> >> processor, and more importantly for me, supports 320 x 240 resolution
> >> LCD screens.  I had thought the hardware and framebuffer were working,
> >> but now I'm not so sure...
> >> 
> >> Attached is a silly test program that writes directly to the framebuffer
> >> - in other words, I'm not using Microwindows here.  Anyway, in
> >> pseudo-code the program looks like this:
> >> 
> >> test:
> >>   open framebuffer
> >>   write all zeros to it (i.e. erase the screen)
> >>   sleep(10) to allow inspection
> >>   lseek to beginning
> >>   write all ones to it (i.e. set all pixels white)
> >>   sleep(10)
> >>   lseek to beginning
> >>   write a pattern of 8x8 multi-colored boxes to screen
> >>   sleep(10)
> >>   close framebuffer
> >> 
> >> Running this shows a nice blank screen for 10 seconds, then a white
> >> screen for 10 seconds, then finally some pretty boxes.  Or at least,
> >> that is what is supposed to happen.
> >> 
> >> What actually happens, sometimes, is that, sometimes it works, other
> >> times the white screen shows the flicker/tearing/shearing throughout the
> >> entire lower two-thirds of the screen.  Of course, the black looks fine,
> >> but surprisingly, the colored blocks also looks fine.  Well, almost -
> >> when the white shows the shearing, there is usually a small black
> >> rectangle, maybe 3-4 pixels wide by 6-8 high, at the far left of the
> >> screen, centered vertically about the first sheared line; this block is
> >> also present on the white screen, along with an 6-8-pixel long vertical
> >> black line at the same elevation, midway across the screen.  I don't
> >> know if that little line shows up with the colored boxes.
> >> 
> >> I don't thing there is anything wrong with my code - it's so simple -
> >> but perhaps I'm missing something?  So it seems to be a framebuffer (or
> >> hardware, of course) problem.  Any ideas?
> >> 
> >> I don't have any familiarity with the framebuffer driver, so just
> >> jumping in is a bit daunting; can anyone point me to a good introduction
> >> on it, or give me a few pointers? 
> >> 
> >> Thanks,
> >> -Bob
> >> 
> >> P.S. I've also posted this on the Microwindows mailing list, because I
> >> had been discussing this problem there before, when I thought it was a
> >> Microwindows problem - please forgive me if you've run into this posting
> >> before...
> >> 
> >> 
> >> ------------------------------------------------------------------------
> >> 
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> >
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Robert S. Grimes

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