topic Re: can't specify ldb parameters on 3.10.53 kernel cmdline in i.MX Processors

can't specify ldb parameters on 3.10.53 kernel cmdline

chris_c — Tue, 12 May 2015 20:04:59 GMT

The 3.10.53 ldb driver appears to have been changed to support device tree nodes. Does this mean there is no longer a way to specify ldb/timings on the command line? This is pretty limiting if your device has several configurations (split mode ldb, versus single lvds channel, with different resolutions). Any ideas on how to use device tree to achieve the same thing?

Re: can't specify ldb parameters on 3.10.53 kernel cmdline

alejandrolozan1 — Tue, 19 May 2015 16:25:17 GMT

Hi,

Regarding the timing parameters, you can use ranges in the device node.

Example:

timing1: timing {

/* 1920x1080p24 */

clock-frequency = <148500000>;

hactive = <1920>;

vactive = <1080>;

hsync-len = <0 44 60>;

hfront-porch = <80 88 95>;

hback-porch = <100 148 160>;

vfront-porch = <0 4 6>;

vback-porch = <0 36 50>;

vsync-len = <0 5 6>;

};

But you can still specify some parameters and display configuration in the bootargs.

For exmaple for LVDS and HDMI dual displays:

U-Boot > setenv displayinfo 'video=mxcfb1:dev=ldb video=mxcfb0:dev=hdmi,

1920x1080M@60,if=RGB24'

Re: can't specify ldb parameters on 3.10.53 kernel cmdline

chris_c — Tue, 07 Jul 2015 20:51:01 GMT

But can you specify whether to use split mode/single channel dynamically in the bootargs?

Re: can't specify ldb parameters on 3.10.53 kernel cmdline

BiyongSUN — Thu, 16 Jul 2015 12:02:38 GMT

Please check the ldb binding guide for device tree

Documentation/devicetree/bindings/video/fsl,ldb.txt

24 Optional properties:

25 - ext-ref: Provide this bool property if your LDB uses an external

26 reference resistor for bandgap.

27 - split-mode: Provide this bool property if your board uses LDB split

28 mode to drive a high resolution display, say 1080P@60. In this

29 mode, two LVDS channels will drive one display.

30 - dual-mode: Provide this bool property if your board uses LDB dual

31 mode to drive two displays. In this mode, one display engine will

32 drive two displays which have the same timings and display content.

display timing is part of linux.