On Wed, 28 Nov 2012 19:07:46 +0100
Stephen Warren [off-list ref] wrote:
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Please read more about bus notifiers. IMHO a good example is provided in 
the following thread:
http://www.mail-archive.com/linux-samsung-soc at vger.kernel.org/msg12238.html

This bus notifier seems enough flexible to afford the variation of
IOMMU map info, like Tegra ASID, which could be platform-specific, and
the other could be common too. There's already iommu_bus_notifier
too. I'll try to implement something base on this.

Experimentally implemented as below. With the followig patch, each
device could specify its own map in DT, and automatically the device
would be attached to the map.

There is a case that some devices share a map. This patch doesn't
suppor such case yet.

From 8cb75bb6f3a8535a077e0e85265f87c1f1289bfd Mon Sep 17 00:00:00 2001
From: Hiroshi Doyu <redacted>
Date: Wed, 28 Nov 2012 14:47:04 +0200
Subject: [PATCH 1/1] ARM: tegra: bus_notifier registers IOMMU devices

platform_bus notifier registers IOMMU devices if dma-window is
specified.

Its format is:
  dma-window = <"start" "size">;
ex)
  dma-window = <0x12345000 0x8000>;

Signed-off-by: Hiroshi Doyu <redacted>
---
 arch/arm/mach-tegra/board-dt-tegra30.c |   40 ++++++++++++++++++++++++++++++++

Shouldn't this patch be to the IOMMU driver itself, not the core Tegra code?

That could be possible and cleaner. I'll check if it works.