On Fri, Aug 15, 2014 at 07:42:28PM +0200, Sebastian Andrzej Siewior wrote: > This is my complete queue fo the omap serial driver based on the 8250 core > code. I played with it on beagle bone, am335x-evm and dra7xx including DMA. > The uncertain remain the runtime-pm pieces. > I hacked a small serial testing application which sent 10x 4KiB of data in > raw mode. The number of interrupts in comparison: > > serial-omap | 8250 omap | 8250 omap + dma | > -------------------------------------------- > TX | 2558 | 641 | 0 + 30 | > RX | 40960 | 854 | 1 + 853 | > > So the 8250 version uses less interrupts for the same amount of data. > The consequence is that in TX mode there should be "short" periods where > no data is sent (before the CPU gets to re-fill the FIFO). On RX we have > a smaller time frame where we have to start to purge the FIFO before it > overflows. Are you saying that with the new driver you have to respond to the RX irq faster than before to avoid overflows? It is not quite clear. I do think 40000 interrupts to handle 40000 bytes of date does seem a tad inefficient, so dropping to 854 looks a lot nicer. Was the omap driver not using the fifo trigger levels at all? -- Len Sorensen -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
