About edma3 controller's default burst size of AM387X.

Hiroki Kato

I uses Texax Instruments TI Sitara AM387X EVM.

I would like to transfer some data from DDR memory to PCIe device with edma3 controller on the board.

When I measured the payload size of dma transfer, that was 64bytes despite PCIe device can receive 128bytes data.

It seems this is limited to DBS(default burst size) of edma3 controller.

Is there any method to transfer larger size?

0 Renjith Thomas over 12 years ago

Guru 31670 points

Dear Kato-san,

You can configure DBS in the register TPTC_CFG. You can configure it to the following values 16, 32, 64 and 128 bytes.

0 Hiroki Kato over 12 years ago in reply to Renjith Thomas

I was able to change DBS with TPTC_CFG and verified 128 bytes palyload packet.

Thanks for your prompt response.

0 Renjith Thomas over 12 years ago in reply to Hiroki Kato

Guru 31670 points

Dear Kato-san,

Just out of curiosity. What is the performance improvement you've got with this change?

0 Hiroki Kato over 12 years ago in reply to Renjith Thomas

Hi Thomas

This is a question from my customer.

he wanted to try to transfer 128byte packet from DDR memory to PCIe device with eDMA controller.

but,he did not know how to change transfer size of the controller.

Your answer resolved his problem.I'm afraid I don't know how the performance changed.

It seems the data transmission efficiency get better.

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