2011-07-19 06:02:58     LCD flicker issue

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2011-07-19 06:02:58     LCD flicker issue

ThangarJ P (INDIA)

Message: 102526   





I am working with BF527 based custom board and the kernel "blackfin-linux-dist-2010R1-RC5".


we have ported our custom LCD driver in this distribution. When we run any network based application along with LCD application  we could see LCD display flickers.


But with 2009 Kernel we didnt observe this flicker.


please find the details of our LCD below.


Type = Giantplus 2.4" LCD


x-resolution = 240


y-resolution = 320


display refresh rate = 45


we enabled the icache and dcache for external memory in the kernel config and remaining configurations are same as 2009 kernel.


kindly clarify


"Is there any difference in handling the interrupts in 2009 and 2010 kernel?"


"Is Reentrancy enabled in 2010 kernel interrupts?"


Kindly suggest what could be the reason for this flickering.






Thank you,







2011-07-19 16:26:37     Re: LCD flicker issue

barreh walid (TUNISIA)

Message: 102543   




You need to give the priority to display DMA.




2011-07-20 00:53:09     Re: LCD flicker issue

ThangarJ P (INDIA)

Message: 102546   




Thank you for your response.




The PPIDMA priority is higher than others.




The below option also enabled in the menu config.




[*] DMA has priority over core for ext. accesses










2011-07-21 08:30:15     Re: LCD flicker issue

ThangarJ P (INDIA)

Message: 102596   




Please anyone clarify my queries.




Thank you,






2011-07-27 01:50:26     Re: LCD flicker issue

svs k (INDIA)

Message: 102672   


I am also a team member of Thangaraj.


With line buffer code, we faced more flickers.


So we moved to standard frame buffer model as in uClinux distribution.  Here we dont face any flickers (as no interrupts). But  We have few clarifications on this.



1. Transition from one image to other image seems to be much slower than line buffer code.


    We guess this may be due to Frame buffer placement in the Non-cacheable DMA region. Because we are doing a 16bit(placed in cacheable region) to 24bit(Non-cacheable DMA buffer) conversion while placing in the frame buffer.


Is our guess right?



2.So  We tried out placing the Frame buffer in cacheable region itself and flushing the cache everytime we write into the frame buffer.


    But we find no improvement in the speed of transition.



Kindly clarify,



will  bfin_dcache_flush_range() function takes more time to flush the entire buffer?











2011-07-27 02:43:40     Re: LCD flicker issue

Aaron Wu (CHINA)

Message: 102673   


So will the standard frame buffer mode meet your requirement? maybe you can post your whole code for us to better understand what's the situation and problem is.




2011-07-27 03:14:28     Re: LCD flicker issue

Michael Hennerich (GERMANY)

Message: 102689    >

Ideally you don't have the first buffer at all.

You video/gui application directly write the pixel format used by the display/PPI

into the non-cacheable DMA region.