[PATCH v4 07/09] iommu/ipmmu-vmsa: Make IMBUSCTR setup optional

[Magnus Damm <magnus.damm@gmail.com>]

From: Magnus Damm <damm+renesas@opensource.se>

Introduce a feature to allow opt-out of setting up
IMBUSCR. The default case is unchanged.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
---

 Changes since V3:
 - None

 Changes since V2:
 - None

 Changes since V1:
 - Updated the commit message
 - Reworked patch to coexist with the multi context feature

 drivers/iommu/ipmmu-vmsa.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- 0025/drivers/iommu/ipmmu-vmsa.c
+++ work/drivers/iommu/ipmmu-vmsa.c	2017-06-19 14:07:06.850607110 +0900
@@ -39,6 +39,7 @@ struct ipmmu_features {
 	bool use_ns_alias_offset;
 	bool has_cache_leaf_nodes;
 	unsigned int number_of_contexts;
+	bool setup_imbuscr;
 };
 
 struct ipmmu_vmsa_device {
@@ -453,9 +454,10 @@ static int ipmmu_domain_init_context(str
 			     domain->cfg.arm_lpae_s1_cfg.mair[0]);
 
 	/* IMBUSCR */
-	ipmmu_ctx_write_root(domain, IMBUSCR,
-			     ipmmu_ctx_read_root(domain, IMBUSCR) &
-			     ~(IMBUSCR_DVM | IMBUSCR_BUSSEL_MASK));
+	if (domain->root->features->setup_imbuscr)
+		ipmmu_ctx_write_root(domain, IMBUSCR,
+				     ipmmu_ctx_read_root(domain, IMBUSCR) &
+				     ~(IMBUSCR_DVM | IMBUSCR_BUSSEL_MASK));
 
 	/*
 	 * IMSTR
@@ -986,6 +988,7 @@ static const struct ipmmu_features ipmmu
 	.use_ns_alias_offset = true,
 	.has_cache_leaf_nodes = false,
 	.number_of_contexts = 1, /* software only tested with one context */
+	.setup_imbuscr = true,
 };
 
 static const struct of_device_id ipmmu_of_ids[] = {