DRA712: how to change VOUT2_DE signal polarity

Anand Mistry

Part Number: DRA712

Tool/software:

Hi,

we are trying to output RGB888 24 bit signal through the vout2 port.

We are able to generate the signal, but we are unable to change the DE signal's polarity.

No matter if select DRM_BUS_FLAG_DE_HIGH or DRM_BUS_FLAG_DE_LOW in the panel_desc.bus_flags, the signal is active low always.

Is there any other location apart from the panel config struct, that we need to change to get DE as active High?

Thanks and Regards,

Anand Mistry

3 months ago

0 Josue Zamitiz-Ayala 3 months ago

TI__Mastermind 31584 points

Hello Anand,

Could you please let me know what SDK version you are using?

-Josue

0 Anand Mistry 3 months ago in reply to Josue Zamitiz-Ayala

Prodigy 20 points

Hi Josue,

We are using Yocto on DRA712. Most likely the SDK version is 6.00.00.03.

The Linux kernel is based on the following tag.

git.ti.com/.../

Thanks and Regards,

Anand Mistry

0 Josue Zamitiz-Ayala 3 months ago in reply to Anand Mistry

TI__Mastermind 31584 points

Hello,

Out of office today due to US holiday.

Thank you for your understanding.

Josue

0 Josue Zamitiz-Ayala 3 months ago in reply to Josue Zamitiz-Ayala

TI__Mastermind 31584 points

Hello Anand,

Standard support for this SW has expired so support for it will be minimal.My first impulse would be to recommend to change the polarity via register write.

Have you tried anything like this?

Also, what driver are you using? can you share the file from which these flags are used?

Anand Mistry said:
DRM_BUS_FLAG_DE_HIGH or DRM_BUS_FLAG_DE_LO

After enquiring with our local Linux display engineer, we have the following next steps:

Can you enable debug messages in the following file https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/drivers/gpu/drm/omapdrm/dss/dispc.c?h=ti-linux-4.19.y

This might help you see if the display control driver is registering the changes.

-Josue

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DRA712: how to change VOUT2_DE signal polarity