[RFC PATCH] iommu/arm-smmu: Add global SMR masking property

On 02/03/17 04:18, Nipun Gupta wrote:

Hi Robin/Will,

This patch is currently not applied on the tree.
I had verified the patch and it seems good.
Is ack required on the patch or do I need to send a non RFC patch (with Robin's signoff)?
This is very much required to support SMMU on NXP platform.

It's still sat in my "patches to do something with" queue - I don't
think we ever reached a concrete decision on the property name for a DT
maintainer ack, but I've tweaked the description per Will's comment;
thanks for the reminder. I'll send an rc1-based version out next week to
reboot the discussion.

Robin.

Thanks,
Nipun

quoted

-----Original Message-----
From: Nipun Gupta
Sent: Sunday, December 18, 2016 2:37
To: Robin Murphy <robin.murphy@arm.com>; iommu at lists.linux-
foundation.org; devicetree at vger.kernel.org; linux-arm-
kernel at lists.infradead.org
Cc: mark.rutland at arm.com; will.deacon at arm.com; Stuart Yoder
[off-list ref]
Subject: RE: [RFC PATCH] iommu/arm-smmu: Add global SMR masking property

quoted

-----Original Message-----
From: iommu-bounces at lists.linux-foundation.org [mailto:iommu-
bounces at lists.linux-foundation.org] On Behalf Of Robin Murphy
Sent: Friday, December 16, 2016 18:49
To: iommu at lists.linux-foundation.org; devicetree at vger.kernel.org; linux-

arm-

quoted

kernel at lists.infradead.org
Cc: mark.rutland at arm.com; will.deacon at arm.com; Stuart Yoder
[off-list ref]
Subject: [RFC PATCH] iommu/arm-smmu: Add global SMR masking property

The current SMR masking support using a 2-cell iommu-specifier is
primarily intended to handle individual masters with large and/or
complex Stream ID assignments; it quickly gets a bit clunky in other SMR
use-cases where we just want to consistently mask out the same part of
every Stream ID (e.g. for MMU-500 configurations where the appended TBU
number gets in the way unnecessarily). Let's add a new property to allow
a single global mask value to better fit the latter situation.

CC: Stuart Yoder <redacted>

Tested-by: Nipun Gupta <redacted>

quoted

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

Compile-tested only...

 Documentation/devicetree/bindings/iommu/arm,smmu.txt | 8 ++++++++
 drivers/iommu/arm-smmu.c                             | 4 +++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.txt

b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
index e862d1485205..98f5cbe5fdb4 100644

--- a/Documentation/devicetree/bindings/iommu/arm,smmu.txt
+++ b/Documentation/devicetree/bindings/iommu/arm,smmu.txt

@@ -60,6 +60,14 @@ conditions.
                   aliases of secure registers have to be used during
                   SMMU configuration.

+- stream-match-mask : Specifies a fixed SMR mask value to combine with
+                  the Stream ID value from every iommu-specifier. This
+                  may be used instead of an "#iommu-cells" value of 2
+                  when there is no need for per-master SMR masks, but
+                  it is still desired to mask some portion of every
+                  Stream ID (e.g. for certain MMU-500 configurations
+                  given globally unique external IDs).
+
 ** Deprecated properties:

 - mmu-masters (deprecated in favour of the generic "iommus" binding) :

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 8f7281444551..f1abcb7dde36 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c

@@ -1534,13 +1534,15 @@ static int arm_smmu_domain_set_attr(struct

iommu_domain *domain,

 static int arm_smmu_of_xlate(struct device *dev, struct of_phandle_args

*args)

quoted

 {
-	u32 fwid = 0;
+	u32 mask, fwid = 0;

 	if (args->args_count > 0)
 		fwid |= (u16)args->args[0];

 	if (args->args_count > 1)
 		fwid |= (u16)args->args[1] << SMR_MASK_SHIFT;
+	else if (!of_property_read_u32(args->np, "stream-match-mask",
&mask))
+		fwid |= (u16)mask << SMR_MASK_SHIFT;

 	return iommu_fwspec_add_ids(dev, &fwid, 1);
 }
--
2.10.2.dirty

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