On 18 October 2012 20:48, Huang Shijie <shijie8@xxxxxxxxx> wrote: > On Thu, Oct 18, 2012 at 5:29 AM, Jassi Brar <jaswinder.singh@xxxxxxxxxx> wrote: >> On 18 October 2012 12:15, Huang Shijie <b32955@xxxxxxxxxxxxx> wrote: >>> 于 2012年10月18日 14:18, Vinod Koul 写道: >>> >>>> Why cant you do start (prepare clock etc) when you submit the descriptor >>>> to dmaengine. Can be done in tx_submit callback. >>>> Similarly remove the clock when dma transaction gets completed. >>> >>> I ever thought this method too. >>> >>> But it will become low efficient in the following case: >>> >>> Assuming the gpmi-nand driver has to read out 1024 pages in one _SINGLE_ >>> read operation. >>> The gpmi-nand will submit the descriptor to dmaengine per page. So with your >>> method, >>> the system will repeat the enable/disable dma clock 1024 time. At every >>> enable/disable dma clock, >>> the system has to enable the clock chain and it's parents ... >>> >>> But with this patch, we only need to enable/disable dma clock one time, just >>> at we select the nand chip. >>> >> If the clock is the dmac's property (not channels'), the toggling >> seems too aggressive. >> You could try using runtime_suspend/resume for clock >> disabling/enabling. How about employing autosuspend with a few ms >> delay? > > Yes, employing the autosuspend is workable method too.o > But it's a little more complicated then this patch. You have to create > a thread or workqueue to > do the job. > I am not sure why you would need to create any thread/workqueue ? Just pm_runtime_put_autosuspend() in drivers/ to see how it works. -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
