Subject: [PATCH v4 1/6] of: iommu: add ptr to OF node arg to of_iommu_configure()

From: [email-masked] (Laurent Pinchart)
Date: Wed, 28 Jan 2015 14:23:03 +0200

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<[email-masked]>
> >>> Cc: Grant Likely<[email-masked]>
> >>> Cc: Rob Herring<[email-masked]>
> >>> Cc: Bjorn Helgaas<[email-masked]>
> >>> Cc: Will Deacon<[email-masked]>
> >>> Cc: Russell King<[email-masked]>
> >>> Cc: Arnd Bergmann<[email-masked]>
> >>> Cc: Suravee Suthikulpanit<[email-masked]>
> >>> 
> >>> Signed-off-by: Murali Karicheri<[email-masked]>
> >>> ---
> >>> 
> >>>   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