iMX6 LVDS flicker only during bootup

[raajeshk88]

I am using iMX6Q/DL/S sabresd based board. I am facing a strange issue where the LVDS display flickers only when there is powerup for few minutes and the flicker dies down and looks normal over time. Strangely during the first bootup the uboot splash screen doesnt flicker but after the system goes into linux and then when issued a reboot the uboot splash also flickers. We are facing only from Yocto sumo + linux 4.9.88 while using morty + linux 4.1.15 we are not facing the issue. 
I went down to check the clk tree there is quite a lot of difference between 2 images (sumo + 4.9.88 & morty + 4.1.15). Any help from someone facing similar issue will be helpful. Thanks

[raajeshk88]

Hi Igor,

     The Quadplus we use is of silicon revision 1.0 does this have any effect on the clock to cause these artifacts? I am using PLL2 as clock source. Thanks

[igorpadykov]

Hi Raajesh

I think it does not matter.

Best regards
igor

[raajeshk88]

Hi Igor,

      We see a backlight blank/reinit for abt 2 msec when using persistent boot as per the patch you said. The backlight seems to ahve some issue on pwm_init and it might need atomic PWM API. Does iMX6 have/support atomic PWM API for linux 4.9.88? Thanks

[igorpadykov]

Hi Raajesh

nxp has special service for help with software customizations:

Commercial Support and Engineering Services | NXP 

Best regards
igor

[raajeshk88]

Hi Igor,

    Thanks.The coloration/artifcats due to some patches applied on mxc_ipuv3_fb.c and i manged to fix them. But only i QP i am getting a flick(blanks for a fraction of second) in the screen when kernel takes over from uboot and the splash screen shifts slightly towards the right. This is not seen in Quad. It does not happen during clk initialisation so i believe there is some other difference between Q/QP. I tried not to PRE/PRG as well but still the same. Hoping to get an insight from you. Thanks

[raajeshk88]

Hi Igor,

     Thanks for the reply. The scenario for me is totally different
1. UBOOT no issues
2. Only when the system goes into Linux kernel we have the flicker only for few minutes with all other display functionalities working good. Later as time goes by it slowly dies down n disappears. Then until the next reboot the display is good and works fine. 

 This is recurring on every reboot. Just to test whether the display is good we tried various image/test using uboot and there is no flickering issue. Only when the system enters linux 4.9.88 we have this issue. Do note that this was not occuring in linux 4.1.15 with the same display. 

[igorpadykov]

Hi Raajesh

those patches were developed to handle exactly the same described by you issues.

Best regards
igor

[raajeshk88]

Hi Igor,

      Does these work with iMX6Quadplus. I can see them working with Quad for persist logo but with Quadplus they display always has clk issues. Thanks

[igorpadykov]

Hi Raajesh

yes it works with iMX6Quadplus.

Best regards
igor

[raajeshk88]

Hi Igor,

    Thanks for the confirmation. The reason i ask is Quad works good with the patch but Quadplus has random colouring/artifacts in display. 

[igorpadykov]

Hi Raajesh

one can check boot logo patches on below link and try to port them :

Patch to support uboot logo keep from uboot to kernel for NXP Linux and Android BSP (HDMI, LCD and L... 

Best regards
igor
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