On Thu, Oct 18, 2012 at 02:45:41PM +0800, Huang Shijie 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 ...
And what if you stop using clk_prepare_enable(), and prepare the clock when the channel is requested and only use clk_enable() in the tx_submit method?