[PATCH v6 5/5] virt: vmgenid: add support for devicetree bindings

[Babis Chalios <bchalios@xxxxxxxxx>]

Extend the vmgenid platform driver to support devicetree bindings.
With this support, hypervisors can send vmgenid notifications to
the virtual machine without the need to enable ACPI.
The bindings are located at:
Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml

Co-authored-by: Sudan Landge <sudanl@xxxxxxxxxx>
Signed-off-by: Babis Chalios <bchalios@xxxxxxxxx>
Reviewed-by: Alexander Graf <graf@xxxxxxxxxx>
---
 drivers/virt/vmgenid.c | 53 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
index 3d93e3fb94c4..9a3c12e5dd6e 100644
--- a/drivers/virt/vmgenid.c
+++ b/drivers/virt/vmgenid.c
@@ -2,12 +2,13 @@
 /*
  * Copyright (C) 2022 Jason A. Donenfeld <Jason@xxxxxxxxx>. All Rights Reserved.
  *
- * The "Virtual Machine Generation ID" is exposed via ACPI and changes when a
+ * The "Virtual Machine Generation ID" is exposed via ACPI or DT and changes when a
  * virtual machine forks or is cloned. This driver exists for shepherding that
  * information to random.c.
  */
 
 #include <linux/acpi.h>
+#include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
@@ -20,6 +21,7 @@ enum { VMGENID_SIZE = 16 };
 struct vmgenid_state {
 	u8 *next_id;
 	u8 this_id[VMGENID_SIZE];
+	int irq;
 };
 
 static void vmgenid_notify(struct device *device)
@@ -43,6 +45,14 @@ vmgenid_acpi_handler(acpi_handle __always_unused handle,
 	vmgenid_notify(dev);
 }
 
+static irqreturn_t
+vmgenid_of_irq_handler(int __always_unused irq, void *dev)
+{
+	vmgenid_notify(dev);
+
+	return IRQ_HANDLED;
+}
+
 static int __maybe_unused
 setup_vmgenid_state(struct vmgenid_state *state, u8 *next_id)
 {
@@ -106,6 +116,35 @@ static int vmgenid_add_acpi(struct device __maybe_unused *dev,
 #endif
 }
 
+static int vmgenid_add_of(struct platform_device *pdev,
+			  struct vmgenid_state *state)
+{
+	u8 *virt_addr;
+	int ret = 0;
+
+	virt_addr = (u8 *)devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(virt_addr))
+		return PTR_ERR(virt_addr);
+
+	ret = setup_vmgenid_state(state, virt_addr);
+	if (ret)
+		return ret;
+
+	ret = platform_get_irq(pdev, 0);
+	if (ret < 0)
+		return ret;
+
+	state->irq = ret;
+	pdev->dev.driver_data = state;
+
+	ret = devm_request_irq(&pdev->dev, state->irq, vmgenid_of_irq_handler,
+			       IRQF_SHARED, "vmgenid", &pdev->dev);
+	if (ret)
+		pdev->dev.driver_data = NULL;
+
+	return ret;
+}
+
 static int vmgenid_add(struct platform_device *pdev)
 {
 	struct vmgenid_state *state;
@@ -116,7 +155,10 @@ static int vmgenid_add(struct platform_device *pdev)
 	if (!state)
 		return -ENOMEM;
 
-	ret = vmgenid_add_acpi(dev, state);
+	if (dev->of_node)
+		ret = vmgenid_add_of(pdev, state);
+	else
+		ret = vmgenid_add_acpi(dev, state);
 
 	if (ret)
 		devm_kfree(dev, state);
@@ -124,6 +166,12 @@ static int vmgenid_add(struct platform_device *pdev)
 	return ret;
 }
 
+static const struct of_device_id vmgenid_of_ids[] = {
+	{ .compatible = "microsoft,vmgenid", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, vmgenid_of_ids);
+
 static const struct acpi_device_id vmgenid_acpi_ids[] = {
 	{ "VMGENCTR", 0 },
 	{ "VM_GEN_COUNTER", 0 },
@@ -136,6 +184,7 @@ static struct platform_driver vmgenid_plaform_driver = {
 	.driver     = {
 		.name   = "vmgenid",
 		.acpi_match_table = vmgenid_acpi_ids,
+		.of_match_table = vmgenid_of_ids,
 	},
 };
 
-- 
2.40.1