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.
thanks Huang Shijie