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path: root/drivers/iommu/arm-smmu.c
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Diffstat (limited to 'drivers/iommu/arm-smmu.c')
-rw-r--r--drivers/iommu/arm-smmu.c15
1 files changed, 12 insertions, 3 deletions
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index ce119cb279c3..0c3b8f1c7225 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -56,6 +56,15 @@
#include "io-pgtable.h"
#include "arm-smmu-regs.h"
+/*
+ * Apparently, some Qualcomm arm64 platforms which appear to expose their SMMU
+ * global register space are still, in fact, using a hypervisor to mediate it
+ * by trapping and emulating register accesses. Sadly, some deployed versions
+ * of said trapping code have bugs wherein they go horribly wrong for stores
+ * using r31 (i.e. XZR/WZR) as the source register.
+ */
+#define QCOM_DUMMY_VAL -1
+
#define ARM_MMU500_ACTLR_CPRE (1 << 1)
#define ARM_MMU500_ACR_CACHE_LOCK (1 << 26)
@@ -398,7 +407,7 @@ static void __arm_smmu_tlb_sync(struct arm_smmu_device *smmu,
{
unsigned int spin_cnt, delay;
- writel_relaxed(0, sync);
+ writel_relaxed(QCOM_DUMMY_VAL, sync);
for (delay = 1; delay < TLB_LOOP_TIMEOUT; delay *= 2) {
for (spin_cnt = TLB_SPIN_COUNT; spin_cnt > 0; spin_cnt--) {
if (!(readl_relaxed(status) & sTLBGSTATUS_GSACTIVE))
@@ -1637,8 +1646,8 @@ static void arm_smmu_device_reset(struct arm_smmu_device *smmu)
}
/* Invalidate the TLB, just in case */
- writel_relaxed(0, gr0_base + ARM_SMMU_GR0_TLBIALLH);
- writel_relaxed(0, gr0_base + ARM_SMMU_GR0_TLBIALLNSNH);
+ writel_relaxed(QCOM_DUMMY_VAL, gr0_base + ARM_SMMU_GR0_TLBIALLH);
+ writel_relaxed(QCOM_DUMMY_VAL, gr0_base + ARM_SMMU_GR0_TLBIALLNSNH);
reg = readl_relaxed(ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);