linux-kernel - [PATCH 2/8] dt-bindings: document PASID property for IOMMU masters

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Date:   Mon, 10 Jun 2019 19:47:08 +0100
From:   Jean-Philippe Brucker <jean-philippe.brucker@....com>
To:     will.deacon@....com
Cc:     joro@...tes.org, robh+dt@...nel.org, mark.rutland@....com,
        robin.murphy@....com, jacob.jun.pan@...ux.intel.com,
        iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        eric.auger@...hat.com
Subject: [PATCH 2/8] dt-bindings: document PASID property for IOMMU masters

On Arm systems, some platform devices behind an SMMU may support the PASID
feature, which offers multiple address space. Let the firmware tell us
when a device supports PASID.

Reviewed-by: Rob Herring <robh@...nel.org>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@....com>
---
Previous discussion on this patch last year:
https://patchwork.ozlabs.org/patch/872275/
I split PASID and stall definitions, keeping only PASID here.
---
 Documentation/devicetree/bindings/iommu/iommu.txt | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/iommu/iommu.txt b/Documentation/devicetree/bindings/iommu/iommu.txt
index 5a8b4624defc..3c36334e4f94 100644
--- a/Documentation/devicetree/bindings/iommu/iommu.txt
+++ b/Documentation/devicetree/bindings/iommu/iommu.txt
@@ -86,6 +86,12 @@ have a means to turn off translation. But it is invalid in such cases to
 disable the IOMMU's device tree node in the first place because it would
 prevent any driver from properly setting up the translations.
 
+Optional properties:
+--------------------
+- pasid-num-bits: Some masters support multiple address spaces for DMA, by
+  tagging DMA transactions with an address space identifier. By default,
+  this is 0, which means that the device only has one address space.
+
 
 Notes:
 ======
-- 
2.21.0