firmware: arm_ffa: Initial support for scheduler receiver interrupt

The Framework uses the schedule receiver interrupt to inform the
receiver’s scheduler that the receiver must be run to handle a pending
notification. A receiver’s scheduler can obtain the description of the
schedule receiver interrupt by invoking the FFA_FEATURES interface.

The delivery of the physical schedule receiver interrupt from the secure
state to the non-secure state depends upon the state of the interrupt
controller as configured by the hypervisor.

The schedule seceiver interrupt is assumed to be a SGI. The Arm GIC
specification defines 16 SGIs. It recommends that they are equally
divided between the non-secure and secure states. OS like Linux kernel
in the non-secure state typically do not have SGIs to spare. The usage
of SGIs in the secure state is however limited. It is more likely that
software in the Secure world does not use all the SGIs allocated to it.

It is recommended that the secure world software donates an unused SGI
to the normal world for use as the schedule receiver interrupt. This
implies that secure world software must configure the SGI in the GIC
as a non-secure interrupt before presenting it to the normal world.

Link: https://lore.kernel.org/r/20231005-ffa_v1-1_notif-v4-8-cddd3237809c@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_ffa/driver.c

@@ -22,15 +22,20 @@
 #define DRIVER_NAME "ARM FF-A"
 #define pr_fmt(fmt) DRIVER_NAME ": " fmt
 
+#include <linux/acpi.h>
 #include <linux/arm_ffa.h>
 #include <linux/bitfield.h>
+#include <linux/cpuhotplug.h>
 #include <linux/device.h>
+#include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mm.h>
+#include <linux/of_irq.h>
 #include <linux/scatterlist.h>
 #include <linux/slab.h>
+#include <linux/smp.h>
 #include <linux/uuid.h>
 
 #include "common.h"
@@ -76,6 +81,10 @@ static inline int ffa_to_linux_errno(int errno)
 	return -EINVAL;
 }
 
+struct ffa_pcpu_irq {
+	struct ffa_drv_info *info;
+};
+
 struct ffa_drv_info {
 	u32 version;
 	u16 vm_id;
@@ -85,6 +94,11 @@ struct ffa_drv_info {
 	void *tx_buffer;
 	bool mem_ops_native;
 	bool bitmap_created;
+	unsigned int sched_recv_irq;
+	unsigned int cpuhp_state;
+	struct ffa_pcpu_irq __percpu *irq_pcpu;
+	struct workqueue_struct *notif_pcpu_wq;
+	struct work_struct irq_work;
 };
 
 static struct ffa_drv_info *drv_info;
@@ -917,34 +931,182 @@ static void ffa_setup_partitions(void)
 	kfree(pbuf);
 }
 
-static int ffa_notifications_setup(void)
+/* FFA FEATURE IDs */
+#define FFA_FEAT_NOTIFICATION_PENDING_INT	(1)
+#define FFA_FEAT_SCHEDULE_RECEIVER_INT		(2)
+#define FFA_FEAT_MANAGED_EXIT_INT		(3)
+
+static irqreturn_t irq_handler(int irq, void *irq_data)
 {
-	int ret;
+	struct ffa_pcpu_irq *pcpu = irq_data;
+	struct ffa_drv_info *info = pcpu->info;
 
-	ret = ffa_features(FFA_NOTIFICATION_BITMAP_CREATE, 0, NULL, NULL);
-	if (ret) {
-		pr_err("Notifications not supported, continuing with it ..\n");
-		return 0;
+	queue_work(info->notif_pcpu_wq, &info->irq_work);
+
+	return IRQ_HANDLED;
+}
+
+static void ffa_sched_recv_irq_work_fn(struct work_struct *work)
+{
+	ffa_notification_info_get();
+}
+
+static int ffa_sched_recv_irq_map(void)
+{
+	int ret, irq, sr_intid;
+
+	/* The returned sr_intid is assumed to be SGI donated to NS world */
+	ret = ffa_features(FFA_FEAT_SCHEDULE_RECEIVER_INT, 0, &sr_intid, NULL);
+	if (ret < 0) {
+		if (ret != -EOPNOTSUPP)
+			pr_err("Failed to retrieve scheduler Rx interrupt\n");
+		return ret;
 	}
 
-	ret = ffa_notification_bitmap_create();
+	if (acpi_disabled) {
+		struct of_phandle_args oirq = {};
+		struct device_node *gic;
+
+		/* Only GICv3 supported currently with the device tree */
+		gic = of_find_compatible_node(NULL, NULL, "arm,gic-v3");
+		if (!gic)
+			return -ENXIO;
+
+		oirq.np = gic;
+		oirq.args_count = 1;
+		oirq.args[0] = sr_intid;
+		irq = irq_create_of_mapping(&oirq);
+		of_node_put(gic);
+#ifdef CONFIG_ACPI
+	} else {
+		irq = acpi_register_gsi(NULL, sr_intid, ACPI_EDGE_SENSITIVE,
+					ACPI_ACTIVE_HIGH);
+#endif
+	}
+
+	if (irq <= 0) {
+		pr_err("Failed to create IRQ mapping!\n");
+		return -ENODATA;
+	}
+
+	return irq;
+}
+
+static void ffa_sched_recv_irq_unmap(void)
+{
+	if (drv_info->sched_recv_irq)
+		irq_dispose_mapping(drv_info->sched_recv_irq);
+}
+
+static int ffa_cpuhp_pcpu_irq_enable(unsigned int cpu)
+{
+	enable_percpu_irq(drv_info->sched_recv_irq, IRQ_TYPE_NONE);
+	return 0;
+}
+
+static int ffa_cpuhp_pcpu_irq_disable(unsigned int cpu)
+{
+	disable_percpu_irq(drv_info->sched_recv_irq);
+	return 0;
+}
+
+static void ffa_uninit_pcpu_irq(void)
+{
+	if (drv_info->cpuhp_state)
+		cpuhp_remove_state(drv_info->cpuhp_state);
+
+	if (drv_info->notif_pcpu_wq)
+		destroy_workqueue(drv_info->notif_pcpu_wq);
+
+	if (drv_info->sched_recv_irq)
+		free_percpu_irq(drv_info->sched_recv_irq, drv_info->irq_pcpu);
+
+	if (drv_info->irq_pcpu)
+		free_percpu(drv_info->irq_pcpu);
+}
+
+static int ffa_init_pcpu_irq(unsigned int irq)
+{
+	struct ffa_pcpu_irq __percpu *irq_pcpu;
+	int ret, cpu;
+
+	irq_pcpu = alloc_percpu(struct ffa_pcpu_irq);
+	if (!irq_pcpu)
+		return -ENOMEM;
+
+	for_each_present_cpu(cpu)
+		per_cpu_ptr(irq_pcpu, cpu)->info = drv_info;
+
+	drv_info->irq_pcpu = irq_pcpu;
+
+	ret = request_percpu_irq(irq, irq_handler, "ARM-FFA", irq_pcpu);
 	if (ret) {
-		pr_err("notification_bitmap_create error %d\n", ret);
+		pr_err("Error registering notification IRQ %d: %d\n", irq, ret);
 		return ret;
 	}
-	drv_info->bitmap_created = true;
 
+	INIT_WORK(&drv_info->irq_work, ffa_sched_recv_irq_work_fn);
+	drv_info->notif_pcpu_wq = create_workqueue("ffa_pcpu_irq_notification");
+	if (!drv_info->notif_pcpu_wq)
+		return -EINVAL;
+
+	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "ffa/pcpu-irq:starting",
+				ffa_cpuhp_pcpu_irq_enable,
+				ffa_cpuhp_pcpu_irq_disable);
+
+	if (ret < 0)
+		return ret;
+
+	drv_info->cpuhp_state = ret;
 	return 0;
 }
 
 static void ffa_notifications_cleanup(void)
 {
+	ffa_uninit_pcpu_irq();
+	ffa_sched_recv_irq_unmap();
+
 	if (drv_info->bitmap_created) {
 		ffa_notification_bitmap_destroy();
 		drv_info->bitmap_created = false;
 	}
 }
 
+static int ffa_notifications_setup(void)
+{
+	int ret, irq;
+
+	ret = ffa_features(FFA_NOTIFICATION_BITMAP_CREATE, 0, NULL, NULL);
+	if (ret) {
+		pr_err("Notifications not supported, continuing with it ..\n");
+		return 0;
+	}
+
+	ret = ffa_notification_bitmap_create();
+	if (ret) {
+		pr_err("notification_bitmap_create error %d\n", ret);
+		return ret;
+	}
+	drv_info->bitmap_created = true;
+
+	irq = ffa_sched_recv_irq_map();
+	if (irq <= 0) {
+		ret = irq;
+		goto cleanup;
+	}
+
+	drv_info->sched_recv_irq = irq;
+
+	ret = ffa_init_pcpu_irq(irq);
+	if (ret)
+		goto cleanup;
+
+	return 0;
+cleanup:
+	ffa_notifications_cleanup();
+	return ret;
+}
+
 static int __init ffa_init(void)
 {
 	int ret;
@@ -1000,7 +1162,11 @@ static int __init ffa_init(void)
 
 	ffa_set_up_mem_ops_native_flag();
 
-	return ffa_notifications_setup();
+	ret = ffa_notifications_setup();
+	if (ret)
+		goto free_pages;
+
+	return 0;
 free_pages:
 	if (drv_info->tx_buffer)
 		free_pages_exact(drv_info->tx_buffer, RXTX_BUFFER_SIZE);