On Dell systems with intel_iommu enabled, dcdbas platform driver's DMA
calls fail with ENOMEM / "DMAR: Allocating domain for dcdbas failed".
This is because the intel-iommu driver only supports PCI bus / devices,
therefore it is not (yet) possible to properly allocate and attach iommu
group/domain and attach devices with no pci parent devices.
This workaround is forcing the intel_iommu implementation to use identity
mapping for this device, using the DUMMY_DEVICE_DOMAIN_INFO constant value
defined and used in intel-iommu.c.
Signed-off-by: Szabolcs Fruhwald <sfruhwald@xxxxxxxxxx>
---
drivers/platform/x86/dcdbas.c | 5 +++++
drivers/platform/x86/dcdbas.h | 2 +-
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/platform/x86/dcdbas.c b/drivers/platform/x86/dcdbas.c
index 88bd7efafe14..a5d6bb1bc590 100644
--- a/drivers/platform/x86/dcdbas.c
+++ b/drivers/platform/x86/dcdbas.c
@@ -652,6 +652,11 @@ static int dcdbas_probe(struct platform_device *dev)
dcdbas_pdev = dev;
+ /* Intel-IOMMU workaround: platform-bus unsupported, force ID-mapping */
+ #if IS_ENABLED(CONFIG_IOMMU_API) && defined(CONFIG_INTEL_IOMMU)
+ dev->dev.archdata.iommu = INTEL_IOMMU_DUMMY_DOMAIN;
+ #endif
+
/* Check if ACPI WSMT table specifies protected SMI buffer address */
error = dcdbas_check_wsmt();
if (error < 0)
diff --git a/drivers/platform/x86/dcdbas.h b/drivers/platform/x86/dcdbas.h
index 52729a494b00..373eb277933a 100644
--- a/drivers/platform/x86/dcdbas.h
+++ b/drivers/platform/x86/dcdbas.h
@@ -54,6 +54,7 @@
#define SMI_CMD_MAGIC (0x534D4931)
#define SMM_EPS_SIG "$SCB"
+#define INTEL_IOMMU_DUMMY_DOMAIN ((void *)-1)
#define DCDBAS_DEV_ATTR_RW(_name) \
DEVICE_ATTR(_name,0600,_name##_show,_name##_store);
@@ -114,4 +115,3 @@ struct smm_eps_table {
} __packed;
#endif /* _DCDBAS_H_ */
-
--
2.20.1.321.g9e740568ce-goog
