DM81xx: MUSB driver with multiple transaction per microframe

Gunter Schmer

Other Parts Discussed in Thread: DM385

Hi all,

We are on PSP 04.04.02 with IPNC RDK 3.5, and this is specifically on a DM385 device, and using the MUSB in device mode for a video over usb product.

We noticed that latency increases when DMA mode (not PIO mode) is selected. Is this a known issue?

Isochronous multiple transactions per microframe does not work in PIO mode as expected and requires DMA mode. In PIO mode if a 3K buffer is queued up, instead of sending 3 1K buffers in 3 transactions within a microframe, it sends one 1K buffer in a microframe, but the requires a total of 3 microframes. Is this expected?

Thanks,

--Gunter

over 12 years ago

0 Randall Fernandes over 12 years ago

Prodigy 10 points

Hey Gunter,

I have modified the following code to get multiple transactions to work in PIO mode. It is in musb_gadget.c near the beginning of the txstate function:

fifo_count = min(max_ep_writesize(musb, musb_ep),
(int)(request->length - request->actual));

was changed to:

fifo_count = min(max_ep_writesize(musb, musb_ep) * (musb_ep->hb_mult + 1),
(int)(request->length - request->actual));

Randall.

0 Gunter Schmer over 12 years ago in reply to Randall Fernandes

TI__Genius 14222 points

Hi PSP team,

could you take a look at the above patch, to see what the impact could be?

Thanks,

--Gunter

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DM81xx: MUSB driver with multiple transaction per microframe