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From: Thierry Reding <thierry.reding@avionic-design.de>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Stephen Warren <swarren@wwwdotorg.org>,
	linux-tegra@vger.kernel.org,
	Grant Likely <grant.likely@secretlab.ca>,
	Rob Herring <rob.herring@calxeda.com>,
	Russell King <linux@arm.linux.org.uk>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Andrew Murray <andrew.murray@arm.com>,
	Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
	devicetree-discuss@lists.ozlabs.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH 05/14] lib: Add I/O map cache implementation
Date: Thu, 10 Jan 2013 21:20:07 +0100	[thread overview]
Message-ID: <20130110202007.GA26139@avionic-0098.adnet.avionic-design.de> (raw)
In-Reply-To: <20130110192417.GA18478@obsidianresearch.com>

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On Thu, Jan 10, 2013 at 12:24:17PM -0700, Jason Gunthorpe wrote:
> On Thu, Jan 10, 2013 at 08:03:27PM +0100, Thierry Reding wrote:
> 
> > > > You'd piece a mapping together, each bus requires 16 64k mappings, a
> > > > simple 2d array of busnr*16 of pointers would do the trick. A more
> > > > clever solution would be to allocate contiguous virtual memory and
> > > > split that up..
>  
> > > Oh, I see. I'm not very familiar with the internals of remapping, so
> > > I'll need to do some more reading. Thanks for the hints.
> > 
> > I forgot to ask. What's the advantage of having a contiguous virtual
> > memory area and splitting it up versus remapping each chunk separately?
> 
> Not alot, really, but it saves you from the pointer array and
> associated overhead. IIRC it is fairly easy to do in the kernel.

I've been investigating this a bit, and one problem is that it will
prevent the driver from ever building as a module because the necessary
functions aren't exported and I'm not sure exporting them would be
acceptable. Currently PCI host controller drivers with MSI support can't
be built as modules because the MSI infrastructure requires it, but I
briefly discussed this with Bjorn at some point and it should be easy to
remove that requirement.

> Arnd's version is good too, but you would be restricted to aligned
> powers of two for the bus number range in the DT, which is probably
> not that big a deal either?

Stephen suggested on IRC that we could try to keep a bit of dynamicity
in the allocation scheme if we create the bus mapping when the first
device on the bus is probed and discard the mapping if no devices are
found.

Sounds like a good plan to me. Does anybody see any potential pitfalls?

Thierry

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  reply	other threads:[~2013-01-10 20:20 UTC|newest]

Thread overview: 93+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-09 20:43 [PATCH 00/14] Rewrite Tegra PCIe driver Thierry Reding
2013-01-09 20:43 ` [PATCH 01/14] of/pci: Provide support for parsing PCI DT ranges property Thierry Reding
2013-01-11  0:06   ` Stephen Warren
2013-01-11  4:02     ` Thierry Reding
2013-01-09 20:43 ` [PATCH 02/14] of/pci: Add of_pci_get_devfn() function Thierry Reding
2013-01-11  0:09   ` Stephen Warren
2013-01-11  4:06     ` Thierry Reding
2013-01-09 20:43 ` [PATCH 03/14] of/pci: Add of_pci_get_bus() function Thierry Reding
2013-01-09 20:43 ` [PATCH 04/14] of/pci: Add of_pci_parse_bus_range() function Thierry Reding
2013-01-09 20:43 ` [PATCH 05/14] lib: Add I/O map cache implementation Thierry Reding
2013-01-09 21:19   ` Arnd Bergmann
2013-01-09 21:54     ` Thierry Reding
2013-01-09 22:10       ` Arnd Bergmann
2013-01-09 23:12         ` Stephen Warren
2013-01-09 23:17           ` Jason Gunthorpe
2013-01-10  7:19             ` Thierry Reding
2013-01-10  9:17               ` Arnd Bergmann
2013-01-10 10:25                 ` Thierry Reding
2013-01-10 18:20                   ` Jason Gunthorpe
2013-01-10 18:55                     ` Thierry Reding
2013-01-10 19:03                       ` Thierry Reding
2013-01-10 19:24                         ` Jason Gunthorpe
2013-01-10 20:20                           ` Thierry Reding [this message]
2013-01-10 21:06                             ` Jason Gunthorpe
2013-01-16 10:18                           ` Thierry Reding
2013-01-16 11:25                             ` Russell King - ARM Linux
2013-01-16 11:52                               ` Thierry Reding
2013-01-10 18:26                   ` Arnd Bergmann
2013-01-10 18:57                     ` Thierry Reding
2013-01-10  7:10         ` Thierry Reding
2013-01-09 21:28   ` Russell King - ARM Linux
2013-01-09 21:57     ` Thierry Reding
2013-01-09 20:43 ` [PATCH 06/14] ARM: pci: Keep pci_common_init() around after init Thierry Reding
2013-02-05 20:41   ` Thierry Reding
2013-02-06 16:30     ` Russell King - ARM Linux
2013-02-06 19:35       ` Thierry Reding
2013-02-06  8:36   ` Thomas Petazzoni
2013-02-06 16:38   ` Linus Walleij
2013-02-07  0:54     ` Arnd Bergmann
2013-02-06 17:07       ` Linus Walleij
2013-02-07  1:20         ` Arnd Bergmann
2013-01-09 20:43 ` [PATCH 07/14] ARM: pci: Allow passing per-controller private data Thierry Reding
2013-01-09 20:43 ` [PATCH 08/14] ARM: tegra: Move tegra_pcie_xclk_clamp() to PMC Thierry Reding
2013-01-09 20:43 ` [PATCH 09/14] ARM: tegra: Move pmc.h to include/mach Thierry Reding
2013-01-11  0:15   ` Stephen Warren
2013-01-11  4:08     ` Thierry Reding
2013-01-09 20:43 ` [PATCH 10/14] PCI: tegra: Move PCIe driver to drivers/pci/host Thierry Reding
2013-01-09 21:22   ` Arnd Bergmann
2013-01-09 21:58     ` Thierry Reding
2013-01-09 22:03       ` Arnd Bergmann
2013-01-10 23:54   ` Stephen Warren
2013-01-11  3:40     ` Thierry Reding
2013-01-11 15:36       ` Arnd Bergmann
2013-01-11 15:45         ` Thierry Reding
2013-01-12 12:36           ` Thierry Reding
2013-01-12 21:12             ` Arnd Bergmann
2013-01-13  9:58               ` Thierry Reding
2013-01-14  9:57                 ` Andrew Murray
2013-01-15 12:08                   ` Thierry Reding
2013-01-15 12:44                     ` Arnd Bergmann
2013-01-15 15:40                       ` Andrew Murray
2013-01-15 21:14                         ` Thierry Reding
2013-01-16 14:00                           ` Arnd Bergmann
2013-01-16 16:17                             ` Andrew Murray
2013-01-16 18:31                               ` Thierry Reding
2013-01-17 15:42                                 ` Andrew Murray
2013-01-17 16:05                                   ` Thierry Reding
2013-01-17 16:22                                     ` Andrew Murray
2013-01-17 20:30                                       ` Thierry Reding
2013-01-18  9:18                                         ` Andrew Murray
2013-01-22 19:29                                       ` Jason Gunthorpe
2013-01-29 13:31                                         ` Andrew Murray
2013-01-11  0:48   ` Stephen Warren
2013-01-11  3:52     ` Thierry Reding
2013-01-11 20:34       ` Stephen Warren
2013-01-18  9:56   ` Andrew Murray
2013-01-18 10:09     ` Thierry Reding
2013-02-13 23:11   ` Thomas Petazzoni
2013-01-09 20:43 ` [PATCH 11/14] ARM: tegra: tamonten: Add PCIe support Thierry Reding
2013-01-09 21:23   ` Arnd Bergmann
2013-01-10 20:21     ` Thierry Reding
2013-01-09 20:43 ` [PATCH 12/14] ARM: tegra: tec: " Thierry Reding
2013-01-11  0:22   ` Stephen Warren
2013-01-11  4:34     ` Thierry Reding
2013-01-09 20:43 ` [PATCH 13/14] ARM: tegra: harmony: Initialize PCIe from DT Thierry Reding
2013-01-10 23:58   ` Stephen Warren
2013-01-09 20:43 ` [PATCH 14/14] ARM: tegra: trimslice: " Thierry Reding
2013-01-10 23:56   ` Stephen Warren
2013-01-11 18:48     ` Thierry Reding
2013-01-09 21:25 ` [PATCH 00/14] Rewrite Tegra PCIe driver Thomas Petazzoni
2013-01-10  6:55   ` Thierry Reding
2013-01-10  8:34     ` Thomas Petazzoni
2013-01-28 18:15 ` Bjorn Helgaas

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