linux-kernel - Re: [PATCH v4 1/6] of: iommu: add ptr to OF node arg to of_iommu

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Message-ID: <3953539.m9NpxSWcJ5@avalon>
Date:	Wed, 28 Jan 2015 14:23:03 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Will Deacon <will.deacon@....com>
Cc:	Murali Karicheri <m-karicheri2@...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()

Hi Will,

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.
> > 
> > Laurent,
> > 
> > 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.

-- 
Regards,

Laurent Pinchart

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