Messages in this thread | | | Subject | Re: Softirq priority inversion from "softirq: reduce latencies" | From | Sebastian Andrzej Siewior <> | Date | Mon, 7 Mar 2016 16:48:14 +0100 |
| |
On 02/27/2016 07:19 PM, Peter Hurley wrote: > Hi Eric,
Hi Peter,
> Because both the uart driver (omap8250) and the dmaengine driver > (edma) were (relatively) new, we assumed there was some race between > starting a new rx DMA and processing the previous one.
Now after digesting the whole thread. I complained about this a long while ago. After you start RX-DMA the DMA-engine is not programmed immediately but deferred into softirq/tasklet. This is not the case for continuous DMA transfer - those are programmed right away.
I don't remember that I found a reason why this simple programming has to be deferred and can't happen immediately like it is the case for the continuous DMA transfers. So I skipped that. RX-DMA in UART was working well but for some reason omap's MMC-card driver refused to work.
Sebastian
| |