On Wednesday 28 January 2015 12:29:42 Will Deacon wrote:

On Wed, Jan 28, 2015 at 12:23:03PM +0000, Laurent Pinchart wrote:

quoted

On Wednesday 28 January 2015 11:33:00 Will Deacon wrote:

quoted

On Mon, Jan 26, 2015 at 06:49:01PM +0000, Murali Karicheri wrote:

quoted

On 01/25/2015 08:32 AM, Laurent Pinchart wrote:

quoted

On Friday 23 January 2015 17:32:34 Murali Karicheri wrote:

quoted

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<redacted>
Cc: Grant Likely<redacted>
Cc: Rob Herring<redacted>
Cc: Bjorn Helgaas<redacted>
Cc: Will Deacon<redacted>
Cc: Russell King<linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>
Cc: Arnd Bergmann<redacted>
Cc: Suravee Suthikulpanit<redacted>

Signed-off-by: Murali Karicheri<redacted>
---

  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.

The only reason that I didn't code that in of_iommu_configure originally is
because I didn't want to go against the binding spec for the initial
version, especially as we didn't have a reason to look at parent nodes.

The only thing to double-check is that we don't break any existing users
of the binding with this change, but I don't think that we do.

-- 
Regards,

Laurent Pinchart