[...]

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+Examples:
+=========
+
+Single-master IOMMU:
+--------------------
+
+	iommu {
+		#iommu-cells = <0>;
+	};
+
+	master {
+		iommus = <&/iommu>;

Nit: this should be iommus = <&{/iommu}>, or it's not valid dts syntax.

Done.

Cheers. I take it that was done for the other occurrences too?

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+	};
+
+Multiple-master IOMMU with fixed associations:
+----------------------------------------------
+
+	/* multiple-master IOMMU */
+	iommu {
+		/*
+		 * Masters are statically associated with this IOMMU and
+		 * address translation is always enabled.
+		 */
+		#iommu-cells = <0>;

I don't follow why translation being always enabled is relevant to the
example; that would seem to be independent from the binding.

Surely the key point is that with no way to distinguish devices, they
presumably share the same translations?

Both aspects are important I think. For #iommu-cells = <0> there is no
way for the IOMMU driver to know how to enable translation for a given
device. So it must be either always on or always off.

Sure. But "always on or off" is not the same as "always enabled", which
was what confused me.

I guess one could say that this is implicit if all masters share the
same translations. And I guess translations don't always have to be on
or off technically. Let me try to rephrase this:

		/*
		 * Masters are statically associated with this IOMMU and share
		 * the same address translations because the IOMMU does not
		 * have sufficient information to distinguish between masters.
		 *
		 * Consequently address translation is always on or off for
		 * all masters at any given point in time.
		 */

Does that sound better?

That addresses my concern, so yes.

Given these are minor and everyone wants this in now, I'm happy for
these to go through in a fixup patch later.

Cheers,
Mark.