AM62A7: DSS Pixel-clock cannot go below ~16MHz (small displays don't work)

user3775977

Part Number: AM62A7

Tool/software:

Hello,

we are currently integrating a small 320x240 pixel display (ST7798 controller), but face the issue, that the DSS controller can't be clocked below 15937500Hz.
The ST7798 requires a pixel clock below 8MHz to operate correctly.

The kernel warns us about that, with the following message:
tidss 30200000.dss: vp1: Clock rate 15937500 differs over 5% from requested 7000000

We tried to adjust the clock for the DSS module with K3 conf, for example with:
k3conf set clock 186 2 7000000

Unfortunately this still doesn't let us go below ~16MHz.

Is there any limitation, that prevents the DSS pixel clock to go to values below 15MHz?
Is this an issue with the tisci firmware?

Thank you!

BWA

over 1 year ago

0 Krunal Bhargav34 over 1 year ago

TI__Mastermind 45065 points

Hi,

Let me check internally and get back to you.

Regards,
Krunal

0 Krunal Bhargav34 over 1 year ago in reply to Krunal Bhargav34

TI__Mastermind 45065 points

Hi,

I was able to replicate the issue and I had a chat with our tisci team. We are looking into the configuration and will keep you posted. Please allow few days because our team is in middle of a release cycle but they will look into the issue shortly.

Regards,
Krunal

0 user3775977 over 1 year ago in reply to Krunal Bhargav34

Prodigy 90 points

Than you, please keep me updated!

Regards
Bernhard

0 Krunal Bhargav34 over 1 year ago in reply to user3775977

TI__Mastermind 45065 points

Hi Bernhard,

The team is still in middle of release and no updates so far. Will keep you posted if there is more progress.

Regards,
Krunal

0 Krunal Bhargav34 over 1 year ago in reply to Krunal Bhargav34

TI__Mastermind 45065 points

Hello,

Apologies for the delayed response but our team has identified a bug with DM firmware. They are working on resolving the issue and the plan is to have a fix for next release (planned for later in the year).

Regards,
Krunal

0 user3775977 over 1 year ago in reply to Krunal Bhargav34

Prodigy 90 points

Hello Kurnal,

ok good.

Is it possible, that you share any pre-release versions of the tisci firmware as soon as it is available(we have a standing NDA with TI and project support)?

We need to verify that our hardware is working asap.
For our project (a 7-digit medical development with a hard timeline) the risk is unfortunately much too high, to wait until "later in the year".

Kind regards
Bernhard Wörndl-Aichriedler

0 Krunal Bhargav34 over 1 year ago in reply to user3775977

TI__Mastermind 45065 points

Hi,

Once we start developing the next SDK release, we will have release candidate available and we can share that with you. As of now, we don't have anything to share with you.

Regards,
Krunal

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AM62A7: DSS Pixel-clock cannot go below ~16MHz (small displays don't work)