On Fri, Mar 16, 2018 at 04:05:10PM -0500, Steve Wise wrote: > > Code includes wmb() followed by writel(). writel() already has a barrier > on > > some architectures like arm64. > > > > This ends up CPU observing two barriers back to back before executing the > > register write. > > > > Since code already has an explicit barrier call, changing writel() to > > writel_relaxed(). > > > > Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx> > > NAK - This isn't correct for PowerPC. For PowerPC, writeX_relaxed() is just > writeX(). ?? Why is changing writex() to writeX() a NAK then? > I was just looking at this with Chelsio developers, and they said the > writeX() should be replaced with __raw_writeX(), not writeX_relaxed(), to > get rid of the extra barrier for all architectures. That doesn't seem semanticaly sane. __raw_writeX() should not appear in driver code, IMHO. Only the arch code can know what the exact semantics of that accessor are.. If ppc can't use writel_relaxed to optimize then we probably need yet another io accessor semantic defined :( Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
