Re: flickering screen with Intel PSM
- From: "Dean Ramsier" <ramsiernospam@xxxxxxxxxx>
- Date: Tue, 29 May 2007 09:10:29 -0400
It's not an IPSM issue, it's a hardware issue. The display subsystem on the
processor requires a lot of bandwidth on the system bus. It is competing
for resources with other devices such as flash memory. If the display DMA
engine is unable to run frequently enough to keep it's output fifo full then
the screen will flicker. The PXA processors have always had this problem.
Some things to look into:
1) Modify display configuration so that it requires less cpu bandwidth.
E.g. reduce the color depth and frame rate as much as possible.
2) Use the most aggressive flash timings available. Make sure you are using
the burst capability of the flash.
3) Investigate running the image from SDRAM since that is faster access.
The cache line fill cycles to rom are blocking the display dma from running,
cache line fills to SDRAM will be much shorter leaving more bandwidth for
the display.
4) Check other devices that access the system bus and ensure their timings
are also as tight as possible
5) Make sure that if you have any variable latency devices, the RDY line
de-asserts as fast as possible when the transfer is complicate (stiff
pullup).
--
Dean Ramsier - eMVP
BSQUARE Corporation
"soreeye" <soreeye@xxxxxxxxxxx> wrote in message
news:ed1imJeoHHA.1240@xxxxxxxxxxxxxxxxxxxxxxx
Hi,
Are you guys using intel PSM?
Thanks and Regards
gol wrote:
Hello to both of you Josh and soreeye,
We have the same problem.
We use PXA270, MainstoneIII. Our display is 640x480.
We are interested in how to solve this issue by software.
Josh, please explain more specifically how to solve it.
soreeye, please let us know when you get to some conclusion.
Thank you very much
"Josh Chang" wrote:
Hi soreeye,
We have the same issue here on Xscale platforms. This is due to the
limit of system bus bandwidth when it comes to higher display
resolution, e.g 640x480 or higher...
You know, display needs constant refreshing, so there is always some
occupancy of system bus.....
Now if you also do some large amount of IO operation to read/write data
from/to your IO device......the system bus bandwidth will be
insufficient for this....then some display data will be lost...this is
what the flickering results from....
The solutions
(1)Hardware engineers, they may have some workaround / or in the
beginning, some design concept that be taken into account while building
up the platforms....
eg. Use some additional display chip, e.g Marathon 2700G to handle the
display data separately....
(2)In software viewpoint, your may adjust the clock of system bus to be
faster to handle the incoming bus busy status And also do some
modification to the IO drivers, such as the ATADISK driver to have
longer wait time.....
Anyway this is a trade off......After all, the RISC is original designed
to be used in some handheld device with lower resolution, isn't it?
Hope this is useful for you...Best Regards, Josh Chang
"soreeye" wrote:
Hi,
Reference on a Mainstone III, our platform is running a Windows CE5
with Intel PSM and ROM-only filesystem.
The system is sharing the OS and user data on the same NOR.
Whenever the system access the NOR flash, the screen will flicker.
Is there anything we can changed to eliminate the flickering of the
screen?
Thanks and Regards
.
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