i.MX6DL LVDS clock issue

[j_wolters]

Hello,

I'm trying to connect a 10.3 LVDS display with 1920x720 resolution. Unfortunately the display stays black. When measuring the display clock it doesn's goes higher then 50mhz instead of configured 89mhz.

I Modified the Device Tree Files like this:

&clks {
  fsl,ldb-di0-parent = <&clks IMX6QDL_CLK_PLL2_PFD0_352M>;
  fsl,ldb-di1-parent = <&clks IMX6QDL_CLK_PLL2_PFD0_352M>; 
};
&ldb { 
status = "okay"; 
lvds-channel@0 { 
reg = <0>; 
fsl,data-mapping = "spwg"; 
fsl,data-width = <24>; 
status = "okay"; primary; 
display-timings { 
native-mode = <&timing0>; 
timing0: 1920x720 { 
clock-frequency = <89000000>; 
hactive = <1920>; 
vactive = <720>; 
hback-porch = <0>; 
hfront-porch = <0>; 
vback-porch = <0>; 
vfront-porch = <0>; 
hsync-len = <112>; 
vsync-len = <10>; 
pixelclk-active = <0>; 
}; }; }; };

Thanks in advance,

Jordan

[j_wolters]

Issue is fixed by changing the "clks" in dtb file.

&clks {
      fsl,ldb-di0-parent = <&clks IMX6QDL_CLK_PLL2_PFD0_352M>;
      fsl,ldb-di1-parent = <&clks IMX6QDL_CLK_PLL2_PFD0_352M>; 
};

to:
&clks {
        assigned-clocks = <&clks IMX6QDL_CLK_LDB_DI0_SEL>, <&clks IMX6QDL_CLK_LDB_DI1_SEL>;
        assigned-clock-parents = <&clks IMX6QDL_CLK_PLL2_PFD0_352M>, <&clks IMX6QDL_CLK_PLL2_PFD0_352M>; 
};

[igorpadykov]

Hi Jordan

one can look at various lcd examples for different resolutions on boundary boards

linux-imx6/imx6qdl-nitrogen6_max.dtsi at boundary-imx_4.9.x_8mq_ga-pass1-ath10k · boundarydevices/li... 

Configuring i.MX6 boards for different screens - Boundary Devices 

Also single channel supports up to 85 MHz (WXGA 1366x768@60)
for bigger resolutions split mode should be used as described in
Table 40-5. Channel Mapping i.MX6SDL Reference Manual
http://www.nxp.com/assets/documents/data/en/reference-manuals/IMX6SDLRM.pdf

Best regards
igor
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[j_wolters]

Hi Igor,

Thanks for your reply. I have display working with correct display clock currently. 

Unfortunately this is with an old yocto and kernel version. For now it works on Yocto 2.1.2 (krogoth) with kernel 4.1.15, but the same dts configuration doesn't work with Yocto 2.5.2 (sumo) and kernel 4.9.88.

Can there be some different lvds configurations in kernel?

Best regard,

Jordan

[igorpadykov]

Hi Jordan

nxp support sumo only starting with L4.14.78 :

linux-imx - i.MX Linux kernel 

For L4.9.88 rocko is used according to Linux 4.9.88_2.0.0 BSP & Multimedia Codecs Documentation

Best regards
igor