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Message-ID: <54C8FE72.3060409@ti.com>
Date: Wed, 28 Jan 2015 10:21:22 -0500
From: Murali Karicheri <m-karicheri2@...com>
To: Will Deacon <will.deacon@....com>
CC: Laurent Pinchart <laurent.pinchart@...asonboard.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
Russell King <linux@....linux.org.uk>,
Arnd Bergmann <arnd@...db.de>, Joerg Roedel <joro@...tes.org>,
Rob Herring <robh+dt@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
"grant.likely@...aro.org" <grant.likely@...aro.org>
Subject: Re: [PATCH v4 1/6] of: iommu: add ptr to OF node arg to of_iommu_configure()
On 01/28/2015 08:32 AM, Will Deacon wrote:
> On Wed, Jan 28, 2015 at 01:15:10PM +0000, Laurent Pinchart wrote:
>> On Wednesday 28 January 2015 12:29:42 Will Deacon wrote:
>>> On Wed, Jan 28, 2015 at 12:23:03PM +0000, Laurent Pinchart wrote:
>>>> On Wednesday 28 January 2015 11:33:00 Will Deacon wrote:
>>>>> On Mon, Jan 26, 2015 at 06:49:01PM +0000, Murali Karicheri wrote:
>>>>>> On 01/25/2015 08:32 AM, Laurent Pinchart wrote:
>>>>>>> On Friday 23 January 2015 17:32:34 Murali Karicheri wrote:
>>>>>>>> Function of_iommu_configure() is called from of_dma_configure() to
>>>>>>>> setup iommu ops using DT property. This API is currently used for
>>>>>>>> platform devices for which DMA configuration (including iommu ops)
>>>>>>>> may come from device's parent. To extend this functionality for PCI
>>>>>>>> devices, this API need to take a parent node ptr as an argument
>>>>>>>> instead of assuming device's parent. This is needed since for PCI,
>>>>>>>> the dma configuration may be defined in the DT node of the root bus
>>>>>>>> bridge's parent device. Currently only dma-range is used for PCI and
>>>>>>>> iommu is not supported. So return error if the device is PCI.
>>>>>>>>
>>>>>>>> Cc: Joerg Roedel<joro@...tes.org>
>>>>>>>> Cc: Grant Likely<grant.likely@...aro.org>
>>>>>>>> Cc: Rob Herring<robh+dt@...nel.org>
>>>>>>>> Cc: Bjorn Helgaas<bhelgaas@...gle.com>
>>>>>>>> Cc: Will Deacon<will.deacon@....com>
>>>>>>>> Cc: Russell King<linux@....linux.org.uk>
>>>>>>>> Cc: Arnd Bergmann<arnd@...db.de>
>>>>>>>> Cc: Suravee Suthikulpanit<Suravee.Suthikulpanit@....com>
>>>>>>>>
>>>>>>>> Signed-off-by: Murali Karicheri<m-karicheri2@...com>
>>>>>>>> ---
>>>>>>>>
>>>>>>>> drivers/iommu/of_iommu.c | 10 ++++++++--
>>>>>>>> drivers/of/platform.c | 2 +-
>>>>>>>> include/linux/of_iommu.h | 6 ++++--
>>>>>>>> 3 files changed, 13 insertions(+), 5 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
>>>>>>>> index af1dc6a..439235b 100644
>>>>>>>> --- a/drivers/iommu/of_iommu.c
>>>>>>>> +++ b/drivers/iommu/of_iommu.c
>>>>>>>> @@ -133,19 +133,25 @@ struct iommu_ops *of_iommu_get_ops(struct
>>>>>>>> device_node *np)
>>>>>>>> return ops;
>>>>>>>> }
>>>>>>>>
>>>>>>>> -struct iommu_ops *of_iommu_configure(struct device *dev)
>>>>>>>> +struct iommu_ops *of_iommu_configure(struct device *dev,
>>>>>>>> + struct device_node *iommu_np)
>>>>>>>> {
>>>>>>>> struct of_phandle_args iommu_spec;
>>>>>>>> struct device_node *np;
>>>>>>>> struct iommu_ops *ops = NULL;
>>>>>>>> int idx = 0;
>>>>>>>>
>>>>>>>> + if (dev_is_pci(dev)) {
>>>>>>>> + dev_err(dev, "iommu is currently not supported for PCI\n");
>>>>>>>> + return NULL;
>>>>>>>> + }
>>>>>>>> +
>>>>>>>> /*
>>>>>>>> * We don't currently walk up the tree looking for a parent
>>>>>>>> IOMMU.
>>>>>>>> * See the `Notes:' section of
>>>>>>>> * Documentation/devicetree/bindings/iommu/iommu.txt
>>>>>>>> */
>>>>>>>
>>>>>>> Wouldn't it be better to fix this rather than passing the device node
>>>>>>> pointer to the function ? The solution would be more generic.
>>>>>>
>>>>>> Will Deacon (Copied here) is working on this as we alteady discussed
>>>>>> in this thread. So it will be addressed by him in another series.
>>>>>
>>>>> Well, "working on this" equates to "has it somewhere near the bottom of
>>>>> a very long list" :)
>>>>
>>>> What's your opinion on this patch then, do you think adding the iommu_np
>>>> argument makes sense as a temporary hack, or should we instead walk up the
>>>> tree looking for an iommus attribute in parent nodes ? I don't expect that
>>>> to be insanely difficult to code.
>>>
>>> If walking up the tree is useful, then I think we should do that and update
>>> the Documentation to reflect the new behaviour.
>>
>> If I understand Murali's patch set right (please correct me if that's not the
>> case) the PCI code walks up the DT nodes hierarchy to the parent node that
>> contains the iommus attribute and passes a pointer to that node to this
>> function. It's thus a PCI-specific solution. As a temporary hack that's OK I
>> suppose, but if implementing it right straight away isn't difficult that would
>> be better.
>
> It looks to me like the code walks the PCI topology to get the DT node for
> the host controller, and passes *that* to of_dma_configure. That sounds
> like the right thing to do to me, especially since the PCI topology is
> likely not encoded in the device-tree. So actually, it is passing the
> first parent node afaict.
>
Laurent, Will,
I don't have an IOMMU hardware to do more work on this. My patch series
has been on this list for long and it is also increasing in scope :(
I would suggest a follow up patch to this from someone (probably Will)
and my patch goes as is with out further update. Hope this is reasonable.
Murali
> The part I'm more interested in is the mapping of RequesterID (PCI dma
> alias) to IOMMU ID when we transition from the PCI topology to the DT
> topology. Currently, it seems to be 1:1 on the platforms I have, but I
> doubt this will always be the case.
>
> Will
--
Murali Karicheri
Linux Kernel, Texas Instruments
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