On Thu, 2015-06-25 at 02:08 +0200, Luis R. Rodriguez wrote: > > OK thanks I'll proceed with these patches then. > > > As for user mappings, > > Which APIs were you considering in this regard BTW? mmap of the generic /sys/bus/pci/.../resource* > > maybe the right thing to do is to let us do what we do by > > default with a quirk that can set a flag in pci_dev to disable that > > behaviour (maybe on a per BAR basis ?). > > That might mean it could restrict userspace WC to require devices > to have WC parts on a full PCI BAR. Although this is restrictive > having reviewed most WC uses in the kernel I'd think this would be > a fair compromise to make, but again, if things are still murky > perhaps best we kiss this idea good bye for now and hope for it > to come in on future buses or ammendments (if that's even possible?). > > > I think the common case is that WC works. > > If WC does not I will note one hack which migh be worth mentioning -- > just for > the record, this was devised as a shortcoming of a device where they > failed to > split things properly and that *without* WC performance suffered quite > a bit so > they made one full PCI BAR WC and as a work around this: > > http://lkml.kernel.org/r/20150416041837.GA5712@hykim-PC > > That is for registers that needed it: > > write; wmb; > > Then if they wanted to wait till the NIC has seen the write, they did: > > write; wmb; read; > Right, and as I mentioned, on some archs like powerpc (and possibly more), writel() and co contains an implicit mb() > Luis-- -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
