PTN3356R1 doesnot work with ls1028

[Gnimis]

Hi,

We have a ls1028 customer  board, build the system by OpenIL V1.10 ,used the configs nxp_ls1028ardb-64b_defconfig.On display, we used PTN3356R1 to convert DisplayPort to VGA. The schematic is refer to the application note(AN11590).

When powered up, the screen show nothing, but according to the booting log we find the DP driver is alread readed the EDID infomations from the screen.

[ 4.836757] [drm] Initialized mali-dp 1.0.0 20160106 for f080000.display on minor 0
[ 4.836774] drivers/gpu/drm/bridge/cadence/cdns-dp-core.c: cdns_dp_connector_detect
[ 4.838083] drivers/gpu/drm/bridge/cadence/cdns-dp-core.c: cdns_dp_connector_get_modes
[ 4.878837] cdns-mhdp-imx f200000.display: 0,ff,ff,ff,ff,ff,ff,0
[ 4.878845] cdns-mhdp-imx f200000.display: mfg_id:30,ae
[ 4.878848] cdns-mhdp-imx f200000.display: prod_code:bf,60
...

 3 questions want to confirm：

1) should I config the registers of the PTN3356? Does it work if the peripheral circuit is okay?

2）Does the linux dts need to be modified? PTN3356 just use DP_LANE0 and DP_LANE1, but the default setting of ls1028ardb is using DP_LANE0~DP_LANE3. the DP lane setting in dts is: 

lane-mapping = <0x4e>;

3)Are there any other settings for DP parameters or LCD controller?

Thanks.

[yipingwang]

About the questions:

1) should I config the registers of the PTN3356? Does it work if the peripheral circuit is okay?

A: We haven’t verified this circuit, not sure it is working on ls1028a.

2）Does the linux dts need to be modified? PTN3356 just use DP_LANE0 and DP_LANE1, but the default setting of ls1028ardb is using DP_LANE0~DP_LANE3. the DP lane setting in dts is:

lane-mapping = <0x4e>;

A: normally lane-mapping should be updated according to the peripheral circuit.

3)Are there any other settings for DP parameters or LCD controller?

A: Normally DP and LCD don’t need update. Pay attention to the power supply of the peripheral circuit.

Some suggestions:

1)

  If possible, please read EDID from PC to make sure the EDID read in linux is correct.

2)

As it worked with DP-to-HDMI converter on LS1028ARDB.

so customer can have a trial with commerial DP-to-VGA converter, e.g. https://item.jd.com/2301318.html (or https://item.jd.com/2388562.html)

If this works fine with commerial DP-to-VGA converter, maybe there is a problem on the schematics.