Once the DMA is completed, your function is done.
一旦DMA完成，函数也即完成。
So how does this wait for the DMA operation to complete?
但这是如何实现等待dma操作完成的呢？
Queue a DMA PUT to transfer the buffer back to main memory.
对DMA PUT 进行排队，从而将缓冲区传输回主内存。
However, there are some legacy systems that do not support DMA.
但是也有很多以前的体系不支持直接存储器存取。
DMA is difficult or impossible to configure in this environment.
DMA是很困难或者不可能在这个环境中使用的。
The "tag" is a number which can be assigned to one or many DMA commands.
“标签”是一个数值，可分配给一个或多个dma命令。
In this scenario, the DMA-based transfer need not shift data later on.
在这种方案中，基于DMA移动就不需要数据移位了。
Others have DMA engines which need to know the real address on the bus.
另外一些带有dma引擎的设备需要知道总线上的真实地址。
The DMA command can also have certain levels of synchronization applied to it.
dma命令也可以应用一些特定级别的同步。
A break above the 21-dma (weekly support) will turn the short-term bias positive.
如突破21日移动均线(本周支撑位)，短期偏见或将转向积极。
The first function is perform_dma, which, not surprisingly, performs DMA commands.
第一个函数是 perform_dma，毫无疑问，该函数执行DMA命令。
The spu_writech command and the spu_mfcstat command are used to verify successful completion of the DMA routine.
spu _ writech命令和spu_mfcstat命令用来验证d ma例程已经成功完成。
The spu_writech command and the spu_mfcstat command are used to verify successful completion of the DMA routine.
spu _ writech命令和spu_mfcstat命令用来验证d ma例程已经成功完成。
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