On Thu, Nov 14, 2019 at 10:33:31AM +0530, Vinod Koul wrote: > On 06-11-19, 20:22, Alexander Gordeev wrote: > > This is a sample implementation of a driver using "avalon-dma" to > > perform data transfers between target device memory and system memory: > > > > +----------+ +----------+ +----------+ > > | RAM |<-->| Avalon |<---PCIe--->| Host | > > +----------+ +----------+ +----------+ > > > > The target device is expected to use only Avalon-MM DMA Interface for > > PCIe to initiate DMA transactions - without custom hardware specifics > > to make such transfers possible. > > > > Unlike "dmatest" driver, the contents of DMAed data is not manipulated by > > "avalon-test" in any way. It is basically pass-through and the the data > > are fully dependent on the target device implementation. Thus, it is up > > to the users to analyze received or provide meaningful transmitted data. > > Is this the only reason why you have not used dmatest. If so, why not > add the feature to dmatest to optionally not check the DMAed data > contents? The main reason is that "dmatest" does not support DMA_SLAVE type of transactions. I considered adding DMA_SLAVE to "dmatest". But it would break the current neat design and does not appear solving the issue of data verification. Simply besause in general DMA_SLAVE case there is no data integrity criteria easily available to the driver. I.e if the data is a sensor image then verifying it in the driver would be pointless. So in case of "avalon-test" I offloaded the task of data verification to the user. The driver itself just streams user data to/from device. In fact, this approach is not "avalon-dma" specific and could be used with any "dmaengine" compatible driver. Moreover, it would be quite useful for bringing up devices in embedded systems. I.e one could master a raw display frame in user space and DMA it via the driver - without graphic stack involved. The only missing functionality I could think of is using DMABUFs, but that is very easy to add. Actually, "avalon-test" is rather a presentation of how I tested "avalon-dma". I understand "dmatest" is more easy to trust and I could probably make it working with DMA_SLAVE type. But that would entail hardware design requirements: - DMA slave should both respond to read and write transactions; - data read should always be the same as data written; I have such version of hardware design, but I doubt majorify of devices out there can honor the above requirements. Summarizing - I would suggest not to change "dmatest" and bring in a generalized version of "avalon-test" if you find it useful for a wider audience. Thanks! > -- > ~Vinod
