AM335x LCD with eDMA

Alex Medina

Other Parts Discussed in Thread: AM3352

Hi!

Can anybody explain me why when I try to use the eDMA with LCD interface the speed of transferring is only about 500 ns per one transfer? The lcd dma can reach up to 220 ns per transfer, but it is not enough flexible.

Can I transfer data faster with edma? (all another interfaces, such as gpmc, gpio, etc work good with edma)

Best regards, Alex

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

What processor is this? What software?

0 Alex Medina over 8 years ago in reply to Biser Gatchev-XID

Intellectual 340 points

The AM3352.
Linux 3.8. I write direct to the PARAM and eDMA registers. Data transfers is correct but slow.

0 Biser Gatchev-XID over 8 years ago in reply to Alex Medina

TI__Guru**** 393215 points

TI does not support this Linux version, but you can check this document to understand how the LCD works:

2744.LCDC.pdf

0 Alex Medina over 8 years ago in reply to Biser Gatchev-XID

Intellectual 340 points

Thank for your reply, but I read this document . It describe how to work with lcd dma, but it is not interesting for me.
I want to use the mode, which I read at the spruh73k : "If an LCD panel is not used, this interface can be used to control any MCU-like peripheral". And I need to use dma to read and write data, but lcd dma can only write.

0 Biser Gatchev-XID over 8 years ago in reply to Alex Medina

TI__Guru**** 393215 points

This note is for the LCD controller working in LIDD mode. There is a note on page 24 of the document I posted above that explains a LIDD DMA issue and workaround. Unfortunately there are no ready Linux drivers for LIDD mode.

0 Alex Medina over 8 years ago in reply to Biser Gatchev-XID

Intellectual 340 points

Yes, it is true. I am writing such driver for LIDD mode by myself now. I can do it at the StartWare, I sure the result will be the same. Apparently, edma for some reason can not transfers to/from lcd without delays.

Thank for your answers!
Best regards, Alex

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AM335x LCD with eDMA