When a buffer is modified by both hardware components such as DMA and by
software components, the buffer cache state must be kept in sync so that
data is not accidentally thrown away during future invalidations.
When polling hardware registers in high performance situations, don't
rely on usleep or other standard sleep functions since they will
necessarily rely on kernel ticks to be woken up. This can easily cause
an immense reduction in throughput.
The changes here ensure correct cache maintenance around DMA operations.
One cache flush was missing and two cache invalidations occurred before
the corresponding read that would make them necessary.
This adds Xilinx's driver for the Xilinx NAND controller embedded in the
ZynqMP SoC. Within that device alone, it is possible to access this
peripheral from MicroBlaze, ARMv7, and ARMv8 cores. This has been added
to the hardware ZynqMP BSPs since QEMU does not support emulation of
this peripheral. This driver supports polled operation only. The
imported files are and should be able to remain unmodified. Import
information is kept in bsps/shared/dev/nand/VERSION.
