iommu/arm-smmu-v3: Parse PASID devicetree property of platform devices

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, which will also be used for PCI
PASID.
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/arm-smmu-v3.c

@@ -289,6 +289,12 @@
 
 #define CTXDESC_CD_1_TTB0_MASK		GENMASK_ULL(51, 4)
 
+/*
+ * When the SMMU only supports linear context descriptor tables, pick a
+ * reasonable size limit (64kB).
+ */
+#define CTXDESC_LINEAR_CDMAX		ilog2(SZ_64K / (CTXDESC_CD_DWORDS << 3))
+
 /* Command queue */
 #define CMDQ_ENT_SZ_SHIFT		4
 #define CMDQ_ENT_DWORDS			((1 << CMDQ_ENT_SZ_SHIFT) >> 3)
@@ -627,6 +633,7 @@ struct arm_smmu_master {
 	u32				*sids;
 	unsigned int			num_sids;
 	bool				ats_enabled;
+	unsigned int			ssid_bits;
 };
 
 /* SMMU private data for an IOMMU domain */
@@ -2559,6 +2566,12 @@ static int arm_smmu_add_device(struct device *dev)
 		}
 	}
 
+	master->ssid_bits = min(smmu->ssid_bits, fwspec->num_pasid_bits);
+
+	if (!(smmu->features & ARM_SMMU_FEAT_2_LVL_CDTAB))
+		master->ssid_bits = min_t(u8, master->ssid_bits,
+					  CTXDESC_LINEAR_CDMAX);
+
 	group = iommu_group_get_for_dev(dev);
 	if (!IS_ERR(group)) {
 		iommu_group_put(group);

drivers/iommu/of_iommu.c

@@ -203,8 +203,12 @@ 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:

include/linux/iommu.h

@@ -579,6 +579,7 @@ struct iommu_group *fsl_mc_device_group(struct device *dev);
  * @ops: ops for this device's IOMMU
  * @iommu_fwnode: firmware handle for this device's IOMMU
  * @iommu_priv: IOMMU driver private data for this device
+ * @num_pasid_bits: number of PASID bits supported by this device
  * @num_ids: number of associated device IDs
  * @ids: IDs which this device may present to the IOMMU
  */
@@ -587,6 +588,7 @@ struct iommu_fwspec {
 	struct fwnode_handle	*iommu_fwnode;
 	void			*iommu_priv;
 	u32			flags;
+	u32			num_pasid_bits;
 	unsigned int		num_ids;
 	u32			ids[1];
 };