[RFC PATCH 44/45] iommu/arm-smmu-v3-kvm: Support power management with SCMI SMC

[Jean-Philippe Brucker]

Discover SCMI parameters for the SMMUv3 power domain, and pass them to
the hypervisor. Power management must use a method based on SMC, so the
hypervisor driver can catch them and keep the software state in sync
with the hardware.

Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
---
 .../iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c   | 76 +++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
index 930d78f6e29f..198e41d808b0 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
@@ -6,6 +6,7 @@
  */
 #include <asm/kvm_mmu.h>
 #include <linux/local_lock.h>
+#include <linux/of_address.h>
 #include <linux/of_platform.h>
 
 #include <kvm/arm_smmu_v3.h>
@@ -495,6 +496,75 @@ static int kvm_arm_smmu_device_reset(struct host_arm_smmu_device *host_smmu)
 	return 0;
 }
 
+static int kvm_arm_probe_scmi_pd(struct device_node *scmi_node,
+				 struct kvm_power_domain *pd)
+{
+	int ret;
+	struct resource res;
+	struct of_phandle_args args;
+
+	pd->type = KVM_POWER_DOMAIN_ARM_SCMI;
+
+	ret = of_parse_phandle_with_args(scmi_node, "shmem", NULL, 0, &args);
+	if (ret)
+		return ret;
+
+	ret = of_address_to_resource(args.np, 0, &res);
+	if (ret)
+		goto out_put_nodes;
+
+	ret = of_property_read_u32(scmi_node, "arm,smc-id",
+				   &pd->arm_scmi.smc_id);
+	if (ret)
+		goto out_put_nodes;
+
+	/*
+	 * The shared buffer is unmapped from the host while a request is in
+	 * flight, so it has to be on its own page.
+	 */
+	if (!IS_ALIGNED(res.start, SZ_64K) || resource_size(&res) < SZ_64K) {
+		ret = -EINVAL;
+		goto out_put_nodes;
+	}
+
+	pd->arm_scmi.shmem_base = res.start;
+	pd->arm_scmi.shmem_size = resource_size(&res);
+
+out_put_nodes:
+	of_node_put(args.np);
+	return ret;
+}
+
+/* TODO: Move this. None of it is specific to SMMU */
+static int kvm_arm_probe_power_domain(struct device *dev,
+				      struct kvm_power_domain *pd)
+{
+	int ret;
+	struct device_node *parent;
+	struct of_phandle_args args;
+
+	if (!of_get_property(dev->of_node, "power-domains", NULL))
+		return 0;
+
+	ret = of_parse_phandle_with_args(dev->of_node, "power-domains",
+					 "#power-domain-cells", 0, &args);
+	if (ret)
+		return ret;
+
+	parent = of_get_parent(args.np);
+	if (parent && of_device_is_compatible(parent, "arm,scmi-smc") &&
+	    args.args_count > 0) {
+		pd->arm_scmi.domain_id = args.args[0];
+		ret = kvm_arm_probe_scmi_pd(parent, pd);
+	} else {
+		dev_err(dev, "Unsupported PM method for %pOF\n", args.np);
+		ret = -EINVAL;
+	}
+	of_node_put(parent);
+	of_node_put(args.np);
+	return ret;
+}
+
 static void *kvm_arm_smmu_alloc_domains(struct arm_smmu_device *smmu)
 {
 	return (void *)devm_get_free_pages(smmu->dev, GFP_KERNEL | __GFP_ZERO,
@@ -513,6 +583,7 @@ static int kvm_arm_smmu_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct host_arm_smmu_device *host_smmu;
 	struct hyp_arm_smmu_v3_device *hyp_smmu;
+	struct kvm_power_domain power_domain = {};
 
 	if (kvm_arm_smmu_cur >= kvm_arm_smmu_count)
 		return -ENOSPC;
@@ -530,6 +601,10 @@ static int kvm_arm_smmu_probe(struct platform_device *pdev)
 	if (ret || bypass)
 		return ret ?: -EINVAL;
 
+	ret = kvm_arm_probe_power_domain(dev, &power_domain);
+	if (ret)
+		return ret;
+
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	size = resource_size(res);
 	if (size < SZ_128K) {
@@ -606,6 +681,7 @@ static int kvm_arm_smmu_probe(struct platform_device *pdev)
 	hyp_smmu->mmio_size = size;
 	hyp_smmu->features = smmu->features;
 	hyp_smmu->iommu.pgtable_cfg = cfg;
+	hyp_smmu->iommu.power_domain = power_domain;
 
 	kvm_arm_smmu_cur++;
 
-- 
2.39.0