On revisions of the PL310 prior to r3p2, the Store Buffer does
not automatically drain. This can cause normal, non-cacheable
writes to be retained when the memory system is idle, leading
to suboptimal I/O performance for drivers using coherent DMA.
This option adds a write barrier to the cpu_idle loop so that,
on systems with an outer cache, the store buffer is drained
explicitly.
not automatically drain. This can cause normal, non-cacheable
writes to be retained when the memory system is idle, leading
to suboptimal I/O performance for drivers using coherent DMA.
This option adds a write barrier to the cpu_idle loop so that,
on systems with an outer cache, the store buffer is drained
explicitly.