iommu/ipmmu-vmsa: Make IMBUSCTR setup optional

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>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/iommu/ipmmu-vmsa.c b/drivers/iommu/ipmmu-vmsa.c
index 7587017972b0..49f2c697b108 100644
--- a/drivers/iommu/ipmmu-vmsa.c
+++ b/drivers/iommu/ipmmu-vmsa.c
@@ -44,6 +44,7 @@ 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 {
@@ -457,9 +458,10 @@ static int ipmmu_domain_init_context(struct ipmmu_vmsa_domain *domain)
                              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->mmu->features->setup_imbuscr)
+                ipmmu_ctx_write_root(domain, IMBUSCR,
+                                     ipmmu_ctx_read_root(domain, IMBUSCR) &
+                                     ~(IMBUSCR_DVM | IMBUSCR_BUSSEL_MASK));
 
         /*
          * IMSTR
@@ -886,6 +888,7 @@ static const struct ipmmu_features ipmmu_features_default = {
         .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[] = {