On Tue, 27 Dec 2011 17:48:32 -0500 Joshua Kinard <kumba@xxxxxxxxxx> wrote: > On 12/27/2011 17:34, Stephen Hemminger wrote: > > > On Tue, 27 Dec 2011 16:29:57 -0500 > > Joshua Kinard <kumba@xxxxxxxxxx> wrote: > > > >> MIPS I/O registers are always memory-mapped, and to prevent the compiler > >> from trying to over-optimize, volatile is used to make sure we always read a > >> value from the hardware and not from some cached value. > > > > Almost every other network driver had memory mapped register. > > The problem is volatile is that the compiler is stupid and wrong. > > Using explicit barriers is preferred and ensures correct and fast > > code. > > > I am somewhat new to driver development, so I do not know all the tricks of > the trade just yet. Do you have references to doing explicit barriers that > I can look at? Might be worth trying on the RTC driver I have to get the > hang of them. > Start by reading volatile considered harmful and memory barriers in kernel Documentation directory. Paul does a better job of explaining it than I could ever do :-)
