Synq buffers over XRT

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1

Hello,

I have an issue when reading and writing to DDR memory via XRT.

For the buffer to be syncronized, buffer.synq_to_device() and buffer.synq_from_device() functions must be used. This is clear, although I don’t know why exactly!!! but this to some level doesn’t apply if I wanna use the DDR memroy as a virtual FIFO.

My IP has the following structure:

void top(float* A, int iter) {
   read_data(float* A, stream_in, iter); // reads buffer "iter" times (including recently written results from write_data below)
   calculate(stream_in, stream_out, iter); // accumulate over read data with new calculations
   write_data(stream_out, float* A, iter); // writes data to buffer "iter" times
}

The reseaon behind this is that the buffer is too large to be saved in memory, and multiple accumulations is needed for my calculate function (some tiling/partitioning approach). So I read the intermediate data, do the accumulation, write the data, and then do it again until it is completed after ‘iter’ times.

The issue occurs exactly when I write the data to the buffer, I need to use the synq.from.device() so when it is read again, it will update. But this does not apply because I use the call function accel.call(BufferA, iter) from the DefaultIP class.

Is there a work around that allow me automatically sync the buffers without the need to call the sync functions? Any suggestions would be much appreciated.

EDIT: one possible fix is to change the IP in such a way, that I use the call function “iter” times, and use the sync functions between each call. But this might results in an overhead due to missed pipelining over the “iter” loop.

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