Re: [PATCH] dma: add new DMA control commands

From: Huang Shijie
Date: Thu Oct 18 2012 - 02:42:20 EST

ä 2012å10æ18æ 14:18, Vinod Koul åé:
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.

Huang Shijie

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