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From: Saravana Kannan <saravanak@google.com>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Will Deacon <will@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	iommu@lists.linux-foundation.org,
	Bjorn Helgaas <bhelgaas@google.com>,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH 0/7] iommu: Permit modular builds of ARM SMMU[v3] drivers
Date: Fri, 1 Nov 2019 14:26:05 -0700	[thread overview]
Message-ID: <CAGETcx_U1huHHT=_xo6ArTWpmKMkr=rAy4ceoVUQv6XZGEDA_w@mail.gmail.com> (raw)
In-Reply-To: <20191101122825.GA318@e121166-lin.cambridge.arm.com>

On Fri, Nov 1, 2019 at 5:28 AM Lorenzo Pieralisi
<lorenzo.pieralisi@arm.com> wrote:
>
> On Fri, Nov 01, 2019 at 12:41:48PM +0100, Jean-Philippe Brucker wrote:
>
> [...]
>
> > > > I'm also wondering about ACPI support.
> > >
> > > I'd love to add ACPI support too, but I have zero knowledge of ACPI.
> > > I'd be happy to help anyone who wants to add ACPI support that allows
> > > ACPI to add device links.
> >
> > It's not as generic as device-tree, each vendor has their own table to
> > describe the IOMMU topology. I don't see a nice way to transpose the
> > add_links() callback there. Links need to be created either in a common
> > path (iommu_probe_device()) or in the APCI IORT driver.
>
> We can create a generic stub that calls into respective firmware
> handling paths (eg iort_dma_setup() in acpi_dma_configure()).
>
> There are three arches booting with ACPI so stubbing it out in
> specific firmware handlers is not such a big deal, less generic
> sure, but not catastrophically bad.

Ok, good to know.

> Obviously this works for IOMMU masters links

It's unclear to me what you are referring to here and it's throwing me
off on the rest of the email.

Did you mean to say "IOMMU master's links"? As in the bus masters
whose accesses go through IOMMUs? And "links" as in device links?

OR

Do you mean device links from bus master devices to IOMMUs here?

> - for resources
> dependencies (eg power domains) it deserves some thought, keeping in
> mind that IOMMUs are static table entries in ACPI and not device objects
> so they are not even capable of expressing eg power resources and
> suchlike.

If you can reword this sentence for me with more context or split it
into separate sentences, I'd appreciate that very much. I'd help me
understand this better and allow me to try to help out.

> Long story short: adding IOMMU masters links in ACPI should be
> reasonably simple, everything else requires further thought.

-Saravana

  reply	other threads:[~2019-11-01 21:26 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-30 14:51 [PATCH 0/7] iommu: Permit modular builds of ARM SMMU[v3] drivers Will Deacon
2019-10-30 14:51 ` [PATCH 1/7] drivers/iommu: Export core IOMMU API symbols to permit modular drivers Will Deacon
2019-10-30 14:51 ` [PATCH 2/7] iommu/of: Request ACS from the PCI core when configuring IOMMU linkage Will Deacon
2019-10-30 14:51 ` [PATCH 3/7] PCI: Export pci_ats_disabled() as a GPL symbol to modules Will Deacon
2019-10-30 20:30   ` Bjorn Helgaas
2019-10-30 14:51 ` [PATCH 4/7] Revert "iommu/arm-smmu: Make arm-smmu-v3 explicitly non-modular" Will Deacon
2019-10-30 14:51 ` [PATCH 5/7] iommu/arm-smmu-v3: Allow building as a module Will Deacon
2019-10-30 19:31   ` Joerg Roedel
2019-10-31 15:42     ` Will Deacon
2019-11-04 19:15       ` Jean-Philippe Brucker
2019-11-08 14:54         ` Will Deacon
2019-11-05 12:15       ` Joerg Roedel
2019-11-08 11:03         ` Will Deacon
2019-10-30 14:51 ` [PATCH 6/7] Revert "iommu/arm-smmu: Make arm-smmu explicitly non-modular" Will Deacon
2019-10-30 23:09   ` Jordan Crouse
2019-10-31 12:03     ` Will Deacon
2019-10-31 15:32       ` Jordan Crouse
2019-10-30 14:51 ` [PATCH 7/7] iommu/arm-smmu: Allow building as a module Will Deacon
2019-10-30 15:22   ` Rob Herring
2019-10-30 15:26     ` Will Deacon
2019-10-30 15:33     ` Robin Murphy
2019-11-04 19:34   ` Isaac J. Manjarres
2019-11-07 12:48     ` Will Deacon
2019-10-30 15:35 ` [PATCH 0/7] iommu: Permit modular builds of ARM SMMU[v3] drivers Robin Murphy
2019-10-30 15:54   ` Will Deacon
2019-10-31  0:57     ` Saravana Kannan
2019-10-31 19:37       ` Jean-Philippe Brucker
2019-10-31 23:34         ` Saravana Kannan
2019-11-01 10:27           ` John Garry
2019-11-01 21:13             ` Saravana Kannan
2019-11-04 12:16               ` John Garry
2019-11-04 13:29                 ` Robin Murphy
2019-11-07  6:11                   ` Saravana Kannan
2019-11-07  9:13                     ` Jean-Philippe Brucker
2019-11-07  6:02                 ` Saravana Kannan
2019-11-01 11:41           ` Jean-Philippe Brucker
2019-11-01 12:28             ` Lorenzo Pieralisi
2019-11-01 21:26               ` Saravana Kannan [this message]
2019-11-04 11:43                 ` Lorenzo Pieralisi
2019-11-07  5:55                   ` Saravana Kannan
2019-11-01 17:21         ` Will Deacon
2019-11-04  7:54           ` Jean-Philippe Brucker
2019-11-07  6:16       ` Saravana Kannan

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