RE: MPC5121e DIU driver - kernel crash writing alpha component

Hi,=20

Pls refer to my comment embedded.=20

-----Original Message-----
From:=20
linuxppc-dev-bounces+hong-jun.chen=3Dfreescale.com@lists.ozlabs.
org=20
[mailto:linuxppc-dev-bounces+hong-jun.chen=3Dfreescale.com@lists
.ozlabs.org] On Behalf Of LD
Sent: Friday, October 23, 2009 3:17 PM
To: Linux ppc mailing list; Lucio Dona'
Subject: MPC5121e DIU driver - kernel crash writing alpha component
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Hi all,
I am working on Freescale MPC5121e evaluation board ADS512101=20
rev. 3 (M34K processor stepping), developing a graphical application.
Just switched to ADS512101 rev. 4, 0M36P processor stepping.
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I have problems with the video framebuffer driver, try to explain:
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- - app is based on microwindows+fltk, framebuffer driver. On=20
rev3 board working ok.
- - rev4 board: using the kernel from ltib 2009/06/02, just=20
adapted fsl-diu-fb.c and .h to support resolution and timings=20
of my lcd panel.
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The board is booting ok (NFS), but my user space app keeps=20
crashing the kernel.
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I noticed that in 0M36P processor stepping there are many=20
changes about the video interface (DIU), correcting some bugs=20
of the previous stepping ; seems that when I write to the ram=20
area which is mapped to Panel0 of the DIU the system randomly hangs.
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After some debugging...
800x480, 32 bits per pixel, using plane1 (first plane, as=20
described in the processor's reference manual).
If, from user space, I write some alpha component !=3D 0 in=20
this plane then I have a complete system crash.
The reference pdf says "There is no alpha component defined=20
for plane1 because there are no planes behind it."
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Sure, panel0 doesn't support alpha function, so you can't operate it.

I did not yet investigate about writing in other planes ;=20
time is short...
For now, patched microwindows driver for writing 0x00 in=20
alpha components, no more hangs.
Reported to Freescale FAE, waiting for some answers.
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Meanwhile: some suggestions about filtering alpha components=20
in the video driver ?

You can replace panel0 with panel1, which can support alpha function.

I was thinking about some sort of double buffering : user space app
(fltk--->microwindows) writes in a buffer, then the driver=20
clears alpha to 0x00 and memcpy to the real video buffer.
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Problems:
- - driver / user space sync. Vertical retrace ? ioctl ?
- - waste of memory, needs double video buffers
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Any suggestions are welcome,
work in progress.
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Regards
Lucio Dona'
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