Re: [PATCH v3 8/9] iommu/arm-smmu: Support non-PCI devices with SMMUv3

On 01/07/16 13:40, Will Deacon wrote:

On Tue, Jun 28, 2016 at 04:48:27PM +0100, Robin Murphy wrote:

quoted

With the device <-> stream ID relationship suitably abstracted and
of_xlate() hooked up, the PCI dependency now looks, and is, entirely
arbitrary. Any bus using the of_dma_configure() mechanism will work,
so extend support to the platform and AMBA buses which do just that.

Signed-off-by: Robin Murphy <redacted>
---

v3: Now actually tested; improve comment about duplicate IDs.

 drivers/iommu/Kconfig       |  2 +-
 drivers/iommu/arm-smmu-v3.c | 42 ++++++++++++++++++++++++++++++++++--------
 2 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index ad0860383cb3..d1c66afefeed 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig

@@ -308,7 +308,7 @@ config ARM_SMMU
 
 config ARM_SMMU_V3
 	bool "ARM Ltd. System MMU Version 3 (SMMUv3) Support"
-	depends on ARM64 && PCI
+	depends on ARM64
 	select IOMMU_API
 	select IOMMU_IO_PGTABLE_LPAE
 	select GENERIC_MSI_IRQ_DOMAIN

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 8ce2a4f9342b..735690e03818 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c

@@ -35,6 +35,8 @@
 #include <linux/pci.h>
 #include <linux/platform_device.h>
 
+#include <linux/amba/bus.h>
+
 #include "io-pgtable.h"
 
 /* MMIO registers */

@@ -1822,6 +1824,25 @@ static void arm_smmu_remove_device(struct device *dev)
 	iommu_fwspec_free(dev);
 }
 
+static struct iommu_group *arm_smmu_device_group(struct device *dev)
+{
+	struct iommu_group *group;
+
+	/*
+	 * The difficulty of efficient stream-ID-to-device lookup prevents us
+	 * from reasonably detecting aliasing outside of PCI buses, but for the
+	 * the same underlying reason (a sparse 32-bit ID space) there's also

extra 'the'

Oops, thanks.

quoted

+	 * little excuse for systems to be wired up with non-unique IDs in the
+	 * first place; consider them unsupported.
+	 */

This is a long-winded way of saying "we don't support aliasing SIDs outside
of PCI".

It is. Someone said of the original terse 2-line comment "Worse: what if
a SID in the DT aliases with a PCI master? It might be nice to have some
basic sanity checking, at least.", so I expanded it to better clarify
why there isn't. I'll try making it a little less florid.

Robin.

Will