iMX6 - Sabre Lite - LVDS colors problem

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iMX6 - Sabre Lite - LVDS colors problem

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maciejbarzowski
Contributor I

Hi, I use LVDS with http://www.yslcd.com.tw/docs/product/B140XTT01.0.pdf. ​ I had a kernel 3.14.28 and u-boot 2015-07-15122. I have a problem with screen colors, when I entered to u-boot comand line, screen show correct colors, but when I boot the linux, the colors are not correct. I attached the pictures.

Thank for o your replay.

https://scontent.xx.fbcdn.net/hphotos-xaf1/v/t34.0-12/10621139_970141133040973_498696122_n.jpg?oh=e9...

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maciejbarzowski
Contributor I

Hi Gary,

I used the formula from your previous post, but when i restart, bootloader had crashed. I changed the hannstar7 settings to my screen settings. Below I attach the equtions which I used:

DISPLAY TIMING:

The maximum clock frequency = (1366+B)*(768+A)*60 < 80MHz

freq=(1366+90)*(768+56)*60=71984640

xres = horizontal valid = 1366 = hactive

left margin = horizontal period - horizontal valid = 1456 - 1366 = 90 = hback-porch

right margin = 0 = hfront-porch

hsync_len = 0 = hsync-len

yres = vertical valid = 768 = vactive

upper margin = vertical period - vertical valid = 824 - 768 = 56 = vback-porch

lower margin = 0 = vfront-porch

vsync_len = 0 = vsync-len

Now I have a black screen. Do you have some idea, what it's wrong?

I attached the screen-shots:

- list of screen settings in fbpanel function

- u-boot printenv

- booting u-boot

- booting a linux

Best Regards,

Maciej

fbpanel.png

kernel1.pngkernel2.pngprintenv.pngu-boot.png

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maciejbarzowski
Contributor I

Hi guys,

Resolution in the new kernel 3.14.28 is changing at u-boot via fbpanel function. I added my resolutions to this function. I have a some idea what should be wrong.

I attached the screenshot from include file of devicetree (imx6qdl-sabresd.dtsi). Pleas pay attention to 'ldb' and 'lcd'. The 'ldb' had a interface_pix_fmt=RGB666 and default_bpp=16, but 'lcd' had a interface_pix_fmt=RGB565 and default_bpp=16. I think, the 'ldb' work with 16 RGB bits like 'lcd' standard. What do you about it? Tommorow i try this and attached the linux and u-boot full log.

fbpanel.jpg

Best regards,

Maciej

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gary_bisson
Senior Contributor III

Hi Maciej,

Actually we (Boundary Devices) provide fb_panel command in U-Boot in order to list the different displays we support and that we can set dynamically in the device tree.

So if your display is not part of the list, you need to either add it to U-Boot source code or define a fb_lvds variable which defines your display timings:

=> setenv fb_lvds <name>:<interface>:<clock-frequency>,<hactive>,<vactive>,<hback-porch>,<hfront-porch>,<vback-porch>,<vfront-porch>,<hsync-len>,<vsync-len>

=> saveenv

=> reset

u-boot-imx6/fbpanel.c at boundary-v2015.07 · boundarydevices/u-boot-imx6 · GitHub

Otherwise you can change it yourself in the device tree but know that:

  • you should be looking at arch/arm/boot/dts/imx6qdl-sabrelite.dtsi (and not sabresd)
  • you should remove the t_lvds aliases so U-Boot cannot overwrite you display setting
  • only "ldb" is useful since it is the LVDS controller where "lcd" in the device tree is only for LCD displays

Regards,

Gary

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi Maciej,

seems this lcd with resolution 1366 x768 is not supported in bsp, so

appropriate kernel boot parameter should be added. One can look at

example on

https://community.freescale.com/thread/373763

Regards,

Gary

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gary_bisson
Senior Contributor III

Hi Maciej,

Can you please copy the full serial output log to pastebin so we can see what is recognized by U-Boot and later configured in the kernel?

Regards,

Gary

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