From: Christoph Hellwig <hch@lst.de>
To: Mark Greer <mgreer@animalcreek.com>
Cc: Christoph Hellwig <hch@lst.de>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
Dale Farnsworth <dale@farnsworth.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: DMA coherency in drivers/tty/serial/mpsc.c
Date: Wed, 26 Jun 2019 08:48:37 +0200 [thread overview]
Message-ID: <20190626064837.GA24531@lst.de> (raw)
In-Reply-To: <20190625163722.GA18626@animalcreek.com>
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 reaѕonably clean way.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Mark Greer <mgreer@animalcreek.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org,
Paul Gortmaker <paul.gortmaker@windriver.com>,
linux-serial@vger.kernel.org,
Dale Farnsworth <dale@farnsworth.org>,
linuxppc-dev@lists.ozlabs.org, Christoph Hellwig <hch@lst.de>
Subject: Re: DMA coherency in drivers/tty/serial/mpsc.c
Date: Wed, 26 Jun 2019 08:48:37 +0200 [thread overview]
Message-ID: <20190626064837.GA24531@lst.de> (raw)
In-Reply-To: <20190625163722.GA18626@animalcreek.com>
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 reaѕonably clean way.
next prev parent reply other threads:[~2019-06-26 6:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 12:26 DMA coherency in drivers/tty/serial/mpsc.c Christoph Hellwig
2019-06-25 12:26 ` Christoph Hellwig
2019-06-25 16:37 ` Mark Greer
2019-06-25 16:37 ` Mark Greer
2019-06-26 6:48 ` Christoph Hellwig [this message]
2019-06-26 6:48 ` Christoph Hellwig
2019-06-26 16:09 ` Mark Greer
2019-06-26 16:09 ` Mark Greer
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