On Mon, 2015-02-02 at 09:33 -0800, Peter Oh wrote: > > The code (as it is before your patch) implies that it's trying to make > > sure that before it continues, any previous writes to the PCIe device's > > registers are posted. The only way to ensure that is to do a read to the > > registers, as the code does now. > Do you know how the read ensure that although the read code does not > check the return value? > Can you explain how a read ensures that posted write reaches PCIe device? You basically have the following sequence: iowrite() ioread() If you look, you'll see that iowrite() is actually done (or should be, or perhaps with appropriate syncs) on an uncached mapping. As a result, the only thing you care about here is the PCIe bus, not the CPU cache flush. And from there on that's just a question of PCIe bus semantics. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
