[PATCH v10 06/15] iommu/tegra241-cmdqv: Restore PROD and CONS after resume

[Pranjal Shrivastava <praan@google.com>]

From: Ashish Mhetre <amhetre@nvidia.com>

PROD and CONS indices for vcmdqs are getting set to 0 after resume.
Because of this the vcmdq is not consuming commands after resume.
Fix this by restoring PROD and CONS indices after resume from
saved pointers.

Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Ashish Mhetre <amhetre@nvidia.com>
Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
index a394bf0f487f..c7989fcd2c62 100644
--- a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
+++ b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
@@ -567,6 +567,16 @@ static int tegra241_vcmdq_hw_init(struct tegra241_vcmdq *vcmdq)
 	/* Configure and enable VCMDQ */
 	writeq_relaxed(vcmdq->cmdq.q.q_base, REG_VCMDQ_PAGE1(vcmdq, BASE));
 
+	/*
+	 * HW Registers reset to 0 when power-cycled. Restore them from their
+	 * SW copies to prevent executing stale/ghost commands after resume.
+	 * Note on RPM: Power-cycles can never happen when VCMDQs are assigned
+	 * to the Guests since the relevant frameworks (IOMMUFD / VFIO) hold
+	 * active PM references preventing suspend while VMs are active.
+	 */
+	writel_relaxed(vcmdq->cmdq.q.llq.prod, REG_VCMDQ_PAGE0(vcmdq, PROD));
+	writel_relaxed(vcmdq->cmdq.q.llq.cons, REG_VCMDQ_PAGE0(vcmdq, CONS));
+
 	ret = vcmdq_write_config(vcmdq, VCMDQ_EN);
 	if (ret) {
 		dev_err(vcmdq->cmdqv->dev,
-- 
2.55.0.979.g7e5102b832-goog