From 2717852bd539f08f0d09461057bb44e8998aab51 Mon Sep 17 00:00:00 2001
From: Jean-Philippe Brucker <jean-philippe@linaro.org>
Date: Thu, 12 Dec 2024 18:04:17 +0000
Subject: [PATCH] BACKPORT: FROMLIST: iommu/arm-smmu-v3-kvm: Probe power
 domains

Try to use SCMI if possible, otherwise rely on HVC to the hypervisor
to notify about power changes, this is ONLY safe if the SMMU resets
to blocking DMA.

Link: https://lore.kernel.org/all/20241212180423.1578358-54-smostafa@google.com/

Bug: 357781595
Bug: 384432312

Change-Id: Ie0cf4a53052514849b06b60235c520da966026a9
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
 .../iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c   | 78 +++++++++++++++++++
 1 file changed, 78 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 674ce2b02a4b..deeed994a131 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
@@ -8,6 +8,7 @@
 #include <asm/kvm_mmu.h>
 
 #include <linux/arm-smccc.h>
+#include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 
@@ -21,6 +22,7 @@ struct host_arm_smmu_device {
 	struct arm_smmu_device		smmu;
 	pkvm_handle_t			id;
 	u32				boot_gbpa;
+	struct kvm_power_domain		power_domain;
 };
 
 #define smmu_to_host(_smmu) \
@@ -654,6 +656,77 @@ 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_warn(dev, "Unknown PM method for %pOF, using HVC\n",
+			 args.np);
+		pd->type = KVM_POWER_DOMAIN_HOST_HVC;
+		pd->device_id = kvm_arm_smmu_cur;
+	}
+	of_node_put(parent);
+	of_node_put(args.np);
+	return ret;
+}
+
 static int kvm_arm_smmu_probe(struct platform_device *pdev)
 {
 	int ret;
@@ -681,6 +754,10 @@ static int kvm_arm_smmu_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	ret = kvm_arm_probe_power_domain(dev, &host_smmu->power_domain);
+	if (ret)
+		return ret;
+
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	size = resource_size(res);
 	if (size < SZ_128K) {
@@ -738,6 +815,7 @@ static int kvm_arm_smmu_probe(struct platform_device *pdev)
 	hyp_smmu->mmio_addr = ioaddr;
 	hyp_smmu->mmio_size = size;
 	hyp_smmu->features = smmu->features;
+	hyp_smmu->iommu.power_domain = host_smmu->power_domain;
 	kvm_arm_smmu_cur++;
 
 	return arm_smmu_register_iommu(smmu, &kvm_arm_smmu_ops, ioaddr);