[PATCH 3/8] iommu/arm-smmu-v3: Support platform SSID

[Jean-Philippe Brucker]

For platform devices that support SubstreamID (SSID), firmware provides
the number of supported SSID bits. Restrict it to what the SMMU supports
and cache it into master->ssid_bits.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
---
 drivers/iommu/arm-smmu-v3.c | 11 +++++++++++
 drivers/iommu/of_iommu.c    |  6 +++++-
 include/linux/iommu.h       |  1 +
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 4d5a694f02c2..3254f473e681 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -604,6 +604,7 @@ struct arm_smmu_master {
 	struct list_head		domain_head;
 	u32				*sids;
 	unsigned int			num_sids;
+	unsigned int			ssid_bits;
 	bool				ats_enabled		:1;
 };
 
@@ -2097,6 +2098,16 @@ static int arm_smmu_add_device(struct device *dev)
 		}
 	}
 
+	master->ssid_bits = min(smmu->ssid_bits, fwspec->num_pasid_bits);
+
+	/*
+	 * If the SMMU doesn't support 2-stage CD, limit the linear
+	 * tables to a reasonable number of contexts, let's say
+	 * 64kB / sizeof(ctx_desc) = 1024 = 2^10
+	 */
+	if (!(smmu->features & ARM_SMMU_FEAT_2_LVL_CDTAB))
+		master->ssid_bits = min(master->ssid_bits, 10U);
+
 	group = iommu_group_get_for_dev(dev);
 	if (!IS_ERR(group)) {
 		iommu_group_put(group);
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index f04a6df65eb8..04f4f6b95d82 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -206,8 +206,12 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
 			if (err)
 				break;
 		}
-	}
 
+		fwspec = dev_iommu_fwspec_get(dev);
+		if (!err && fwspec)
+			of_property_read_u32(master_np, "pasid-num-bits",
+					     &fwspec->num_pasid_bits);
+	}
 
 	/*
 	 * Two success conditions can be represented by non-negative err here:
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 519e40fb23ce..b91df613385f 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -536,6 +536,7 @@ struct iommu_fwspec {
 	struct fwnode_handle	*iommu_fwnode;
 	void			*iommu_priv;
 	u32			flags;
+	u32			num_pasid_bits;
 	unsigned int		num_ids;
 	u32			ids[1];
 };
-- 
2.21.0