Re: DMA coherency in drivers/tty/serial/mpsc.c

From: Mark Greer
Date: Wed Jun 26 2019 - 12:09:38 EST

On Wed, Jun 26, 2019 at 08:48:37AM +0200, Christoph Hellwig wrote:
> On Tue, Jun 25, 2019 at 09:37:22AM -0700, Mark Greer wrote:
> > Yeah, the mpsc driver had lots of ugly cache related hacks because of
> > cache coherency bugs in the early version of the MV64x60 bridge chips
> > that it was embedded in. That chip is pretty much dead now and I've
> > removed core support for it from the powerpc tree. Removing the mpsc
> > driver is on my todo list but I've been busy and lazy. So, to sum it
> > up, don't spend any more time worrying about it as it should be removed.
> >
> > I'll post a patch to do that tonight and I'm sorry for any time you've
> > spent looking at it so far.
> No problem. And if future such broken chips show up we now have
> support for per-device DMA coherency settings and could actually
> handle it in a reaÑonably clean way.

Ah, good to know - thanks.

BTW, I just submitted a patch to remove the driver.