Difference between revisions of "LVDS"

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(Created page with " === * How to Enable LVDS Module === ---- '''1. Driver Compile'''<br/> Ensure below configures have been selected: <pre><code>CONFIG_ROCKCHIP_LVDS=y</code> </pre> Bellow dr...")
 
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=== * How to Enable LVDS Module ===
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= References =
  
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----
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[https://github.com/rockchip-linux/kernel/tree/release-4.4/drivers/media/platform/rockchip-rga source code]
  
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'''1. Driver Compile'''<br/> Ensure below configures have been selected:
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[https://github.com/rockchip-linux/kernel/blob/release-4.4/Documentation/devicetree/bindings/display/rockchip/rockchip-lvds.txt device-tree document]
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<pre><code>CONFIG_ROCKCHIP_LVDS=y</code>
 
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</pre>
 
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Bellow drivers have been compiled:
 
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<pre><code>drivers/gpu/drm/rockchip/rockchip_lvds.c</code>
 
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</pre>
 
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'''2. DTS Setting'''<br/> 2.1 Enable LVDS Device Node：
 
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*Include the SoC DTS 'rk3288.dtsi' file.
 
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*Set the LVDS device node state to 'okay'.
 
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<pre><code>include "rk3288.dtsi"
 
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&lvds {
 
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        status = "okay";
 
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};</code>
 
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</pre>
 
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2.2 LVDS device node parameters, there're four properties for LVDS device:
 
  
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*"rockchip,data-mapping": stand for the output data mapping, avaliable values "jeida" or "vesa".
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&nbsp;
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*"rockchip,data-width": stand for the output data width, avaliable values "<24>" or "<18>". ("<24>" means RGB888, "<18>" means RGB666)
 
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*"rockchip,ouput": stand for the output connector type, avaliable values "rgb", "lvds" or "duallvds".
 
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*"rockchip,panel": pointed to panel device node (more panel detail, please see link: xxxx )
 
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<pre><code>rockchip,data-mapping = "jeida";
 
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rockchip,data-width = <24>;
 
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rockchip,output = "lvds";
 
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rockchip,panel = <&lvds_panel>;</code>
 
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</pre>
 
  
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----
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= Tips =
  
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=== * How To Debug LVDS Module ===
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== Whether LVDS display card has been registered successfully ==
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'''3. Whether LVDS display card has been registered successfully'''
 
  
 
If the LVDS display card has been created, it would create a sysfs debug directory.
 
If the LVDS display card has been created, it would create a sysfs debug directory.
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*Check the kernel log for more detail (dmesg | grep lvds)  
 
*Check the kernel log for more detail (dmesg | grep lvds)  
  
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'''4. Check LVDS display card status: status, enabled, modes'''
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== Check LVDS display card status: status, enabled, modes ==
 
<pre><code>$ cd /sys/class/drm/card0-LVDS-1
 
<pre><code>$ cd /sys/class/drm/card0-LVDS-1
 
$ cat status  # should printed "connected" or "disconnected"
 
$ cat status  # should printed "connected" or "disconnected"
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</pre>
 
</pre>
  
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'''5. If you still have no picture on LVDS panel, please check bellow information:'''
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== If you still have no picture on LVDS panel, please check bellow information: ==
  
 
*Check the LVDS panel power supply.  
 
*Check the LVDS panel power supply.  
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*Check the hardware connected status, or test the panel on workable board.  
 
*Check the hardware connected status, or test the panel on workable board.  
  
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----
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=== &nbsp; ===
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=== * Reference LVDS DTS Configure： ===
 
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<pre><code>include "rk3288.dtsi"
 
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lvds_panel: lvds_panel {
 
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        compatible ="auo,b101ew05","simple-panel";
 
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        backlight = <&backlight>;
 
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        enable-gpios = <&gpio7 4 GPIO_ACTIVE_HIGH>;
 
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        pinctrl-0 = <&lcd_cs>;
 
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        status = "okay";
 
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        ports {
 
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                panel_in_lvds: endpoint {
 
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                        remote-endpoint = <&lvds_out_panel>;
 
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                };
 
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        };
 
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};
 
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&lvds {
 
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        rockchip,data-mapping = "jeida";
 
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        rockchip,data-width = <24>;
 
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        rockchip,output = "lvds";
 
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        status = "okay";
 
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        ports {
 
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                lvds_out: port@1 {
 
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                        reg = <1>;
 
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                        #address-cells = <1>;
 
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                        #size-cells = <0>;
 
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                        lvds_out_panel: endpoint@0 {
 
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                            reg = <0>;
 
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                                remote-endpoint = <&panel_in_lvds>;
 
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                        };
 
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                };
 
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        };
 
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};</code></pre>
 

Revision as of 02:50, 11 October 2017

References

source code

device-tree document

 

Tips

Whether LVDS display card has been registered successfully

If the LVDS display card has been created, it would create a sysfs debug directory. 

<code>$ ls /sys/class/drm/card0-LVDS-1</code>

So you just need to check that directory. If that directory is missing in your machine board, please check:

  • Whether LVDS have been enabled in DTS files.
  • Whether LVDS panel have been registered successfully.
  • Whether you have available VOP module for LVDS.
  • Check the kernel log for more detail (dmesg | grep lvds)

Check LVDS display card status: status, enabled, modes

<code>$ cd /sys/class/drm/card0-LVDS-1
$ cat status  # should printed "connected" or "disconnected"
$ cat enabled # should printed "enabled" or "disabled"
$ cat modes   # should printed the available mode list, like 1536x2048</code>

If you still have no picture on LVDS panel, please check bellow information:

  • Check the LVDS panel power supply.
  • Check the panel datasheet, ensure you have configured the timing and data format rightly.
  • Check the hardware connected status, or test the panel on workable board.

 

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