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From: Rui Salvaterra <rsalvaterra@gmail.com>
To: hch@lst.de
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: use generic DMA mapping code in powerpc V4
Date: Mon, 10 Dec 2018 17:04:46 +0000
Message-ID: <CALjTZvb4+Ox5Jdm-xwQuxMDz_ub=mHAgPLA4NgrVNZTmUZwhnQ@mail.gmail.com> (raw)
In-Reply-To: <20181208171746.GB15228@lst.de>

On Sat, 8 Dec 2018 at 17:17, Christoph Hellwig <hch@lst.de> wrote:
>
> On Sun, Dec 02, 2018 at 05:11:02PM +1100, Benjamin Herrenschmidt wrote:
> > Talking of which ... Christoph, not sure if we can do something about
> > this at the DMA API level or keep hacks but some adapters such as the
> > nVidia GPUs have a HW hack we can use to work around their limitations
> > in that case.
> >
> > They have a register that can program a fixed value for the top bits
> > that they don't support.
> >
> > This works fine for any linear mapping with an offset, provided they
> > can program the offset in that register and they have enough DMA range
> > to cover all memory from that offset.
> >
> > I can probably get the info about this from them so we can exploit it
> > in nouveau.
>
> I think we can expose the direct mapping offset if people care enough,
> we just have to be very careful designing the API.  I'll happily leave
> that to those that actually want to use it, but I'll gladly help
> reviewing it.

Hi, Christoph and Ben,

It just came to my mind (and this is most likely a stupid question,
but still)… Is there any possibility of these changes having an
(positive) effect on the long-standing problem of Power Mac machines
with AGP graphics cards (which have to be limited to PCI transfers,
otherwise they'll hang, due to coherence issues)? If so, I have a G4
machine where I'd gladly test them.

Thanks,

Rui

  reply index

Thread overview: 127+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-29 19:45 Rui Salvaterra
2018-11-30 10:32 ` Christoph Hellwig
2018-11-30 11:44   ` Rui Salvaterra
2018-11-30 16:41     ` Rui Salvaterra
2018-12-02  6:11     ` Benjamin Herrenschmidt
2018-12-08 17:17       ` Christoph Hellwig
2018-12-10 17:04         ` Rui Salvaterra [this message]
2018-12-10 19:33           ` Christoph Hellwig
2018-12-10 20:03             ` Rui Salvaterra
2018-12-10 20:49             ` Benjamin Herrenschmidt
2018-12-11  9:37               ` Rui Salvaterra
  -- strict thread matches above, loose matches on Subject: below --
2018-11-14  8:22 Christoph Hellwig
2018-11-27  7:42 ` Christoph Hellwig
2018-11-27 22:05   ` Benjamin Herrenschmidt
2018-11-28 11:05   ` Michael Ellerman
2018-11-28 15:55     ` Christian Zigotzky
2018-11-28 20:02       ` Christian Zigotzky
2018-11-28 20:35       ` Michal Suchánek
2018-11-29 17:03         ` Christoph Hellwig
2019-12-19 13:54       ` Christian Zigotzky
2018-11-29 12:05     ` Christian Zigotzky
2018-11-29 15:30       ` Christian Zigotzky
2018-11-29 17:03       ` Christoph Hellwig
2018-11-29 23:07         ` Christian Zigotzky
2018-11-30 10:53           ` Christoph Hellwig
2018-11-30 12:23             ` Christian Zigotzky
2018-11-30 13:10               ` Christoph Hellwig
2018-11-30 15:29                 ` Christian Zigotzky
2018-12-04  7:31                   ` Christian Zigotzky
2018-12-04  9:53                     ` Christian Zigotzky
2018-12-04 14:24                       ` Christoph Hellwig
2018-12-05  9:44                         ` Christian Zigotzky
2018-12-05 14:05                           ` Christoph Hellwig
2018-12-06 10:55                             ` Christian Zigotzky
2018-12-06 17:10                               ` Christian Zigotzky
2018-12-06 19:36                                 ` Christoph Hellwig
2018-12-07  7:48                                   ` Christian Zigotzky
2018-12-07 13:45                               ` Christian Zigotzky
2018-12-07 18:33                                 ` Christian Zigotzky
2018-12-08 10:29                                   ` Christian Zigotzky
2018-12-08 13:47                                     ` Christian Zigotzky
2018-12-09 14:20                                       ` Christian Zigotzky
2018-12-09 18:26                                         ` Christian Zigotzky
2018-12-10 15:54                                           ` Christian Zigotzky
2018-12-11 14:28                                             ` Christian Zigotzky
2018-12-11 18:17                                               ` Christian Zigotzky
2018-12-12  0:47                                                 ` Benjamin Herrenschmidt
2018-12-12  7:03                                                   ` Christian Zigotzky
2018-12-12 14:15                                                 ` Christoph Hellwig
2018-12-12 14:39                                                   ` Christian Zigotzky
2018-12-13  8:41                                                     ` Christian Zigotzky
2018-12-13  9:10                                                       ` Christoph Hellwig
2018-12-13  9:47                                                         ` Christian Zigotzky
2018-12-13 11:19                                                           ` Christian Zigotzky
2018-12-13 11:25                                                             ` Christoph Hellwig
2018-12-13 13:34                                                               ` Christian Zigotzky
2018-12-13 17:48                                                                 ` Christian Zigotzky
2018-12-13 21:53                                                                   ` Christian Zigotzky
2018-12-14 12:00                                                                     ` Christian Zigotzky
2018-12-14 16:45                                                                       ` Christoph Hellwig
2019-01-03  7:36                                                                       ` Christoph Hellwig
2019-01-03 19:26                                                                         ` Christian Zigotzky
2019-01-05 16:03                                                                           ` Christian Zigotzky
2019-01-09  9:31                                                                             ` Christian Zigotzky
2019-01-11  2:10                                                                               ` Christian Zigotzky
2019-01-12 18:14                                                                                 ` Christian Zigotzky
2019-01-15  8:07                                                                                   ` Christian Zigotzky
2019-01-15  8:49                                                                                     ` Christian Zigotzky
2019-01-15 10:55                                                                                       ` Christian Zigotzky
2019-01-15 13:35                                                                                         ` Christoph Hellwig
2019-01-15 13:56                                                                                           ` Christian Zigotzky
2019-01-15 15:17                                                                                             ` Christoph Hellwig
2019-01-17  9:21                                                                                               ` Christian Zigotzky
2019-01-17  9:31                                                                                                 ` Christoph Hellwig
2019-01-17  9:44                                                                                                   ` Christian Zigotzky
2019-01-18  8:35                                                                                                 ` Christoph Hellwig
2019-01-18 11:10                                                                                                   ` Christian Zigotzky
2019-01-18 11:28                                                                                                     ` Christoph Hellwig
2019-01-18 12:07                                                                                                       ` Christian Zigotzky
2019-01-18 12:18                                                                                                         ` Christoph Hellwig
2019-01-18 12:46                                                                                                           ` Christian Zigotzky
2019-01-18 12:55                                                                                                             ` Christoph Hellwig
2019-01-18 15:06                                                                                                               ` Christian Zigotzky
2019-01-19 11:40                                                                                                                 ` Christian Zigotzky
2019-01-19 11:52                                                                                                                   ` Christian Zigotzky
2019-01-19 13:02                                                                                                                     ` Christoph Hellwig
2019-01-19 14:04                                                                                                                       ` Christoph Hellwig
2019-01-21 14:38                                                                                                                         ` Christian Zigotzky
2019-01-23 14:34                                                                                                                           ` Christian Zigotzky
2019-01-25 13:37                                                                                                                             ` Christian Zigotzky
2019-01-27 13:13                                                                                                                               ` Christian Zigotzky
2019-01-28  7:04                                                                                                                                 ` Christoph Hellwig
2019-01-28 16:22                                                                                                                                   ` Christoph Hellwig
2019-01-28 16:52                                                                                                                                     ` Christian Zigotzky
2019-01-29 15:03                                                                                                                                       ` Christian Zigotzky
2019-01-29 16:14                                                                                                                                         ` Christoph Hellwig
2019-01-29 16:34                                                                                                                                           ` Christoph Hellwig
2019-01-30  4:40                                                                                                                                             ` Christian Zigotzky
2019-01-31 12:48                                                                                                                                               ` Christian Zigotzky
2019-02-01  8:04                                                                                                                                                 ` Christoph Hellwig
2019-02-01 16:54                                                                                                                                                   ` Christian Zigotzky
2019-02-03 16:49                                                                                                                                                     ` Christian Zigotzky
2019-02-04  7:56                                                                                                                                                       ` Christoph Hellwig
2019-02-04 12:13                                                                                                                                                         ` Christian Zigotzky
2019-02-04 12:38                                                                                                                                                           ` Christoph Hellwig
2019-02-06 13:45                                                                                                                                                             ` Christian Zigotzky
2019-02-06 15:15                                                                                                                                                               ` Christoph Hellwig
2019-02-06 15:16                                                                                                                                                                 ` Christoph Hellwig
2019-02-07  4:34                                                                                                                                                                   ` Christian Zigotzky
2019-02-08  9:01                                                                                                                                                                     ` Christian Zigotzky
2019-02-08  9:18                                                                                                                                                                       ` Christoph Hellwig
2019-02-08 10:59                                                                                                                                                                         ` Christian Zigotzky
2019-02-09 19:26                                                                                                                                                                         ` Darren Stevens
2019-02-09 21:10                                                                                                                                                                         ` Darren Stevens
2019-02-11  7:41                                                                                                                                                                           ` Christoph Hellwig
2019-02-10 12:00                                                                                                                                                                         ` Christian Zigotzky
     [not found]                                                                                                                                                                           ` <0042290A-2939-4EBA-A638-D404FA2055ED@xenosoft.de>
2019-02-11  7:21                                                                                                                                                                             ` Christian Zigotzky
2019-02-11  7:38                                                                                                                                                                           ` Christoph Hellwig
2019-02-12 12:42                                                                                                                                                                             ` Christian Zigotzky
2019-02-12 15:25                                                                                                                                                                               ` Christoph Hellwig
2019-02-12 19:31                                                                                                                                                                                 ` Christian Zigotzky
2019-02-12 19:50                                                                                                                                                                                   ` Christian Zigotzky
2019-02-12 19:52                                                                                                                                                                                     ` Christoph Hellwig
2018-11-29 17:02     ` Christoph Hellwig
2018-12-08 17:03 ` Christoph Hellwig
2018-12-16 16:51 ` Christoph Hellwig
2018-12-17  1:14   ` Michael Ellerman

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