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From: Murali Karicheri <m-karicheri2@ti.com>
To: Will Deacon <will.deacon@arm.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	Russell King <linux@arm.linux.org.uk>,
	Arnd Bergmann <arnd@arndb.de>, Joerg Roedel <joro@8bytes.org>,
	Rob Herring <robh+dt@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	"suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>,
	"grant.likely@linaro.org" <grant.likely@linaro.org>
Subject: Re: [PATCH v4 1/6] of: iommu: add ptr to OF node arg to of_iommu_configure()
Date: Wed, 28 Jan 2015 10:21:22 -0500	[thread overview]
Message-ID: <54C8FE72.3060409@ti.com> (raw)
In-Reply-To: <20150128133219.GM1569@arm.com>

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@8bytes.org>
>>>>>>>> Cc: Grant Likely<grant.likely@linaro.org>
>>>>>>>> Cc: Rob Herring<robh+dt@kernel.org>
>>>>>>>> Cc: Bjorn Helgaas<bhelgaas@google.com>
>>>>>>>> Cc: Will Deacon<will.deacon@arm.com>
>>>>>>>> Cc: Russell King<linux@arm.linux.org.uk>
>>>>>>>> Cc: Arnd Bergmann<arnd@arndb.de>
>>>>>>>> Cc: Suravee Suthikulpanit<Suravee.Suthikulpanit@amd.com>
>>>>>>>>
>>>>>>>> Signed-off-by: Murali Karicheri<m-karicheri2@ti.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

  reply	other threads:[~2015-01-28 20:38 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-23 22:32 [PATCH v4 0/6] PCI: get DMA configuration from parent device Murali Karicheri
2015-01-23 22:32 ` [PATCH v4 1/6] of: iommu: add ptr to OF node arg to of_iommu_configure() Murali Karicheri
2015-01-25 13:32   ` Laurent Pinchart
2015-01-26 18:49     ` Murali Karicheri
2015-01-28 11:33       ` Will Deacon
2015-01-28 12:23         ` Laurent Pinchart
2015-01-28 12:29           ` Will Deacon
2015-01-28 13:15             ` Laurent Pinchart
2015-01-28 13:32               ` Will Deacon
2015-01-28 15:21                 ` Murali Karicheri [this message]
2015-01-28 23:32                 ` Laurent Pinchart
2015-01-29 14:59                   ` Murali Karicheri
2015-01-29 16:49                   ` Rob Herring
2015-01-30  0:24                     ` Laurent Pinchart
2015-01-30 15:23                       ` Murali Karicheri
2015-01-23 22:32 ` [PATCH v4 2/6] of: move of_dma_configure() to device.c to help re-use Murali Karicheri
2015-01-23 22:32 ` [PATCH v4 3/6] of: fix size when dma-range is not used Murali Karicheri
2015-01-27 11:27   ` Robin Murphy
2015-01-27 15:44     ` Murali Karicheri
2015-01-27 18:55     ` Murali Karicheri
2015-01-28 11:05       ` Catalin Marinas
2015-01-28 15:45         ` Rob Herring
2015-01-28 17:23           ` Catalin Marinas
2015-01-28 17:34           ` Murali Karicheri
2015-01-28 15:55         ` Robin Murphy
2015-01-28 17:30           ` Catalin Marinas
2015-01-30 18:06             ` Murali Karicheri
2015-02-02 12:18               ` Catalin Marinas
2015-02-02 16:10                 ` Murali Karicheri
2015-02-05 21:42                 ` Murali Karicheri
2015-02-05 22:44                   ` Catalin Marinas
2015-01-23 22:32 ` [PATCH v4 4/6] of/pci: add of_pci_dma_configure() update dma configuration Murali Karicheri
2015-01-23 23:41   ` Bjorn Helgaas
2015-01-26 23:25     ` Murali Karicheri
2015-01-26 23:59       ` Bjorn Helgaas
2015-01-27 18:14         ` Murali Karicheri
2015-01-27 18:42           ` Bjorn Helgaas
2015-01-27 18:45             ` Murali Karicheri
2015-01-23 22:32 ` [PATCH v4 5/6] PCI: update dma configuration from DT Murali Karicheri
2015-01-23 23:27   ` Bjorn Helgaas
2015-01-26 23:28     ` Murali Karicheri
2015-01-23 22:32 ` [PATCH v4 6/6] arm: dma-mapping: updates to limit dma_mask and iommu mapping size Murali Karicheri
2015-01-27 11:12   ` Robin Murphy
2015-01-27 11:34     ` Catalin Marinas
2015-01-27 15:19       ` Murali Karicheri

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