[PATCH v2 16/28] drm/panthor: Add AM_RESOURCE_GROUP support

[Karunika Choo]

Add resource-group probing for the arbitration device, including MMIO
resources, IRQ handling, per-AW AM message helpers, handshake
negotiation, and retry work for deferred outgoing messages.

Hook resource groups into arbitration init, teardown, and runtime PM.

Signed-off-by: Karunika Choo <karunika.choo@xxxxxxx>
---
v2:
- Revert child node parsing from v1.
- Tighten protocol validation and reject incompatible messages.
- Drain pending messages on suspend.
- Fixes the following issues raised by sashiko:
  - Simplify and clean up rutnime PM handling and termination paths.
  - change message retry work to delayed work.
  - Add irq_lock to prevent MMIO access as a result of shared IRQ while
    GPU is powered off.
  - Fix irq number storage.
  - Add check for allocation failure from devm_kasprintf
- Link: https://lore.kernel.org/all/20260922205638.7B1DE1F000FF@xxxxxxxxxxxxxxx/
v1:
- Updated DT structure and accompanying parsing to handle child nodes
  instead of named platform resources.
- Hold runtime PM reference during message retries.
- Fix suspend resume ordering.

 drivers/gpu/drm/panthor/arbitration/Makefile  |   3 +-
 .../panthor/arbitration/panthor_arbitration.h |   5 +
 .../arbitration/panthor_arbitration_drv.c     |  15 +
 .../arbitration/panthor_resource_group.c      | 373 ++++++++++++++++++
 .../arbitration/panthor_resource_group.h      |  20 +
 5 files changed, 415 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/panthor/arbitration/panthor_resource_group.c
 create mode 100644 drivers/gpu/drm/panthor/arbitration/panthor_resource_group.h

diff --git a/drivers/gpu/drm/panthor/arbitration/Makefile b/drivers/gpu/drm/panthor/arbitration/Makefile
index b0b6b2e3edf8d..2d2684321d978 100644
--- a/drivers/gpu/drm/panthor/arbitration/Makefile
+++ b/drivers/gpu/drm/panthor/arbitration/Makefile
@@ -4,7 +4,8 @@
 obj-$(CONFIG_DRM_PANTHOR_ARBITRATION) += panthor_arbitration.o
 panthor_arbitration-y := \
 	panthor_arbitration_drv.o \
-	panthor_partition_control.o
+	panthor_partition_control.o \
+	panthor_resource_group.o
 
 INCLUDES = \
 	-I$(src)/..
diff --git a/drivers/gpu/drm/panthor/arbitration/panthor_arbitration.h b/drivers/gpu/drm/panthor/arbitration/panthor_arbitration.h
index fc3610aefae29..9612bfc6c4417 100644
--- a/drivers/gpu/drm/panthor/arbitration/panthor_arbitration.h
+++ b/drivers/gpu/drm/panthor/arbitration/panthor_arbitration.h
@@ -9,8 +9,10 @@
 
 struct device;
 struct panthor_partition_control;
+struct panthor_resource_group;
 
 #define AM_ARB_MAX_PC_COUNT			1
+#define AM_ARB_MAX_RG_COUNT			1
 #define AM_ARB_MAX_AW_COUNT			16
 
 /**
@@ -22,6 +24,9 @@ struct panthor_arbitration {
 
 	/** @pc: Pointer array to partition control data */
 	struct panthor_partition_control *pc[AM_ARB_MAX_PC_COUNT];
+
+	/** @rg: Pointer array to resource group data */
+	struct panthor_resource_group *rg[AM_ARB_MAX_RG_COUNT];
 };
 
 #endif
diff --git a/drivers/gpu/drm/panthor/arbitration/panthor_arbitration_drv.c b/drivers/gpu/drm/panthor/arbitration/panthor_arbitration_drv.c
index a27d24c3679fa..0e8ffd3c1e6da 100644
--- a/drivers/gpu/drm/panthor/arbitration/panthor_arbitration_drv.c
+++ b/drivers/gpu/drm/panthor/arbitration/panthor_arbitration_drv.c
@@ -12,6 +12,7 @@
 
 #include "panthor_arbitration.h"
 #include "panthor_partition_control.h"
+#include "panthor_resource_group.h"
 
 #define PANTHOR_PM_AUTOSUSPEND_DELAY_MS 100
 
@@ -20,6 +21,10 @@ static int panthor_arbitration_runtime_suspend(struct device *dev)
 	struct panthor_arbitration *adev = dev_get_drvdata(dev);
 	int ret = 0;
 
+	ret = panthor_resource_group_suspend(adev);
+	if (ret)
+		return ret;
+
 	ret = panthor_partition_control_suspend(adev);
 	if (ret)
 		return ret;
@@ -36,6 +41,10 @@ static int panthor_arbitration_runtime_resume(struct device *dev)
 	if (ret)
 		return ret;
 
+	ret = panthor_resource_group_resume(adev);
+	if (ret)
+		return ret;
+
 	return 0;
 }
 
@@ -66,6 +75,10 @@ static int panthor_arbitration_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_term;
 
+	ret = panthor_resource_group_init(adev);
+	if (ret)
+		goto err_term;
+
 	ret = of_platform_populate(dev->of_node, NULL, NULL, dev);
 	if (ret)
 		goto err_depopulate;
@@ -81,6 +94,7 @@ static int panthor_arbitration_probe(struct platform_device *pdev)
 	of_platform_depopulate(dev);
 
 err_term:
+	panthor_resource_group_term(adev);
 	panthor_partition_control_term(adev);
 	pm_runtime_put_sync_suspend(dev);
 
@@ -106,6 +120,7 @@ static void panthor_arbitration_remove(struct platform_device *pdev)
 	pm_runtime_disable(adev->dev);
 
 	panthor_partition_control_term(adev);
+	panthor_resource_group_term(adev);
 
 	if (ret >= 0)
 		pm_runtime_put_noidle(adev->dev);
diff --git a/drivers/gpu/drm/panthor/arbitration/panthor_resource_group.c b/drivers/gpu/drm/panthor/arbitration/panthor_resource_group.c
new file mode 100644
index 0000000000000..e413cfd9e6d25
--- /dev/null
+++ b/drivers/gpu/drm/panthor/arbitration/panthor_resource_group.c
@@ -0,0 +1,373 @@
+// SPDX-License-Identifier: GPL-2.0 or MIT
+/* Copyright 2026 ARM Limited. All rights reserved. */
+
+#include <linux/interrupt.h>
+#include <linux/iopoll.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/property.h>
+#include <linux/workqueue.h>
+
+#include "panthor_am_msg.h"
+#include "panthor_arbitration.h"
+#include "panthor_device_io.h"
+#include "panthor_resource_group.h"
+
+#define AM_RG_IRQ_RAWSTAT			0x80
+#define AM_RG_IRQ_CLEAR				0x84
+#define AM_RG_IRQ_MASK				0x88
+#define AM_RG_IRQ_STATUS			0x8C
+#define   AM_RG_MESSAGE_MASK			GENMASK(15, 0)
+
+#define AM_RG_AW_MESSAGE(n)			(0x100 + (n) * 0x20)
+
+#define AM_RG_RETRY_DELAY_US			10
+
+struct rg_aw_data {
+	/** @msg: Messaging data */
+	struct panthor_am_msg msg;
+};
+
+struct panthor_resource_group {
+	/** @dev: Device pointer */
+	struct device *dev;
+
+	/** @name: Resource name */
+	char *name;
+
+	/** @iomem: CPU mapping of the partition control IOMEM region */
+	void __iomem *iomem;
+
+	/** @irq: IRQ number */
+	int irq;
+
+	/** @irq_lock: Lock protecting IRQ state. */
+	spinlock_t irq_lock;
+
+	/** @irq_suspended: Flag indicating if IRQ was suspended. */
+	bool irq_suspended;
+
+	/** @aw_data: Data for each access window */
+	struct rg_aw_data aw_data[AM_ARB_MAX_AW_COUNT];
+
+	/** @wq: Resource group workqueue */
+	struct workqueue_struct *wq;
+
+	/** @msg_retry_work: Work to retry sending pending messages */
+	struct delayed_work msg_retry_work;
+};
+
+static void rg_retry_messages(struct work_struct *work)
+{
+	struct panthor_resource_group *rg = container_of(
+		work, struct panthor_resource_group, msg_retry_work.work);
+	bool retry = false;
+	int ret;
+
+	ret = pm_runtime_resume_and_get(rg->dev);
+	if (ret) {
+		dev_warn(rg->dev, "Failed to resume to retry messages");
+		return;
+	}
+
+	for (u8 aw_id = 0; aw_id < AM_ARB_MAX_AW_COUNT; aw_id++) {
+		struct panthor_am_msg *msg = &rg->aw_data[aw_id].msg;
+		int ret;
+
+		ret = panthor_am_msg_retry(msg);
+		if (ret == -EBUSY || ret == -EAGAIN)
+			retry = true;
+
+		if (ret == -EINVAL)
+			dev_warn(rg->dev, "AW%u send FIFO unexpectedly empty", aw_id);
+	}
+
+	if (retry)
+		mod_delayed_work(rg->wq, &rg->msg_retry_work,
+				 usecs_to_jiffies(AM_RG_RETRY_DELAY_US));
+
+	pm_runtime_put_autosuspend(rg->dev);
+}
+
+static void rg_send_msg(struct panthor_resource_group *rg, u8 aw_id,
+			u64 message)
+{
+	int ret;
+
+	ret = panthor_am_msg_send(&rg->aw_data[aw_id].msg, message);
+	if (ret == -ENOSPC)
+		dev_err(rg->dev, "AW%u send FIFO is full", aw_id);
+
+	if (ret == -EBUSY) {
+		dev_dbg(rg->dev, "AW%u has pending messages, scheduling retry work", aw_id);
+		mod_delayed_work(rg->wq, &rg->msg_retry_work,
+				 usecs_to_jiffies(AM_RG_RETRY_DELAY_US));
+	}
+}
+
+static void rg_send_init_msg(struct panthor_resource_group *rg, u8 aw_id,
+			     u8 ack, u8 version)
+{
+	u64 message = ARB_VM_INIT_MAKE(ack, version);
+
+	rg_send_msg(rg, aw_id, message);
+}
+
+static void rg_respond_to_handshake(struct panthor_resource_group *rg,
+				    u8 aw_id, u64 message)
+{
+	struct rg_aw_data *aw_data = &rg->aw_data[aw_id];
+	bool acked = AM_MSG_ACK_GET(message);
+	u8 version = AM_MSG_VERSION_GET(message);
+	u8 reply_version = AM_MSG_CURRENT_VERSION;
+	int ret;
+
+	ret = panthor_am_msg_version_validate(&aw_data->msg, version, acked,
+					      &reply_version);
+	if (ret == -EOPNOTSUPP)
+		dev_warn(rg->dev,
+			 "AW%u protocol version (%u) not supported (min: %u, max: %u)",
+			 aw_id, version, AM_MSG_MIN_SUPPORTED_VERSION,
+			 AM_MSG_CURRENT_VERSION);
+
+	/* AW initiated the handshake, reply with supported version */
+	if (!acked)
+		rg_send_init_msg(rg, aw_id, 1, reply_version);
+}
+
+static void rg_handshake_init(struct panthor_resource_group *rg)
+{
+	for (u8 aw_id = 0; aw_id < AM_ARB_MAX_AW_COUNT; aw_id++)
+		rg_send_init_msg(rg, aw_id, 0, AM_MSG_CURRENT_VERSION);
+}
+
+static void rg_handle_message(struct panthor_resource_group *rg, u8 aw_id,
+			      u64 message)
+{
+	struct rg_aw_data *aw_data = &rg->aw_data[aw_id];
+	u8 msg_id = AM_MSG_ID_GET(message);
+
+	if (!msg_id)
+		return;
+
+	if (msg_id == VM_ARB_INIT) {
+		rg_respond_to_handshake(rg, aw_id, message);
+		return;
+	}
+
+	if (!panthor_am_msg_supported(&aw_data->msg)) {
+		dev_warn_ratelimited(
+			rg->dev, "Unsupported AW%u (message protocol)", aw_id);
+		return;
+	}
+
+	switch (msg_id) {
+	case VM_ARB_GPU_REQUEST:
+		/* TODO: on_request */
+		break;
+	case VM_ARB_GPU_STOPPED:
+		/* TODO: on_idle */
+		break;
+	default:
+		dev_warn(rg->dev, "Invalid message (0x%llx)", message);
+		break;
+	}
+}
+
+static irqreturn_t rg_irq_raw_handler(int irq, void *data)
+{
+	struct panthor_resource_group *rg = data;
+	unsigned long message_mask;
+	u32 status;
+	u8 aw_id;
+
+	scoped_guard(spinlock_irqsave, &rg->irq_lock) {
+		if (rg->irq_suspended)
+			return IRQ_NONE;
+	}
+
+	status = gpu_read(rg->iomem, AM_RG_IRQ_STATUS);
+	if (!status)
+		return IRQ_NONE;
+
+	message_mask = status;
+	for_each_set_bit(aw_id, &message_mask, AM_ARB_MAX_AW_COUNT) {
+		u64 message = panthor_am_msg_read(&rg->aw_data[aw_id].msg);
+
+		rg_handle_message(rg, aw_id, message);
+	}
+
+	gpu_write(rg->iomem, AM_RG_IRQ_CLEAR, status);
+
+	return IRQ_HANDLED;
+}
+
+static void rg_drain_pending_messages(struct panthor_resource_group *rg)
+{
+	unsigned long message_mask;
+	u8 aw_id;
+
+	if (pm_runtime_status_suspended(rg->dev))
+		return;
+
+	message_mask = gpu_read(rg->iomem, AM_RG_IRQ_RAWSTAT) & AM_RG_MESSAGE_MASK;
+
+	for_each_set_bit(aw_id, &message_mask, AM_ARB_MAX_AW_COUNT) {
+		u64 message = panthor_am_msg_read(&rg->aw_data[aw_id].msg);
+
+		rg_handle_message(rg, aw_id, message);
+	}
+
+	gpu_write(rg->iomem, AM_RG_IRQ_CLEAR, message_mask);
+}
+
+static void rg_irq_suspend(struct panthor_resource_group *rg)
+{
+	scoped_guard(spinlock_irqsave, &rg->irq_lock) {
+		rg->irq_suspended = true;
+
+		if (!pm_runtime_status_suspended(rg->dev))
+			gpu_write(rg->iomem, AM_RG_IRQ_MASK, 0);
+	}
+
+	synchronize_irq(rg->irq);
+}
+
+static void rg_irq_resume(struct panthor_resource_group *rg)
+{
+	guard(spinlock_irqsave)(&rg->irq_lock);
+	rg->irq_suspended = false;
+	gpu_write(rg->iomem, AM_RG_IRQ_MASK, AM_RG_MESSAGE_MASK);
+}
+
+int panthor_resource_group_suspend(struct panthor_arbitration *adev)
+{
+	for (int i = 0; i < AM_ARB_MAX_RG_COUNT; i++) {
+		struct panthor_resource_group *rg = adev->rg[i];
+
+		if (!rg)
+			continue;
+
+		rg_irq_suspend(rg);
+		rg_drain_pending_messages(rg);
+	}
+
+	return 0;
+}
+
+int panthor_resource_group_resume(struct panthor_arbitration *adev)
+{
+	for (int i = 0; i < AM_ARB_MAX_RG_COUNT; i++) {
+		struct panthor_resource_group *rg = adev->rg[i];
+
+		if (!rg)
+			continue;
+
+		rg_irq_resume(rg);
+	}
+
+	return 0;
+}
+
+void panthor_resource_group_term(struct panthor_arbitration *adev)
+{
+	for (int i = 0; i < AM_ARB_MAX_RG_COUNT; i++) {
+		struct panthor_resource_group *rg = adev->rg[i];
+
+		if (!rg)
+			continue;
+
+		disable_delayed_work_sync(&rg->msg_retry_work);
+		rg_irq_suspend(rg);
+	}
+}
+
+static int resource_group_init(struct panthor_arbitration *adev, int i)
+{
+	struct panthor_resource_group *rg;
+	struct device *dev = adev->dev;
+	struct irq_data *irqdata;
+	struct resource *res;
+	void __iomem *iomem;
+	u32 irq_flags = 0;
+	char *name;
+	int irq;
+	int ret;
+
+	if (adev->rg[i])
+		return dev_warn_probe(dev, -ENODEV,
+				      "resource-group %u already present", i);
+
+	rg = devm_kzalloc(dev, sizeof(*rg), GFP_KERNEL);
+	if (!rg)
+		return -ENOMEM;
+
+	name = devm_kasprintf(dev, GFP_KERNEL, "rg%d", i);
+	if (!name)
+		return -ENOMEM;
+
+	res = platform_get_resource_byname(to_platform_device(dev),
+					   IORESOURCE_MEM, name);
+	if (!res)
+		return -ENODEV;
+
+	iomem = devm_ioremap_resource(dev, res);
+	if (IS_ERR(iomem))
+		return dev_err_probe(dev, PTR_ERR(iomem), "%s: Failed to ioremap", name);
+
+	rg->name = name;
+	rg->dev = dev;
+	rg->iomem = iomem;
+
+	spin_lock_init(&rg->irq_lock);
+	rg->irq_suspended = true;
+
+	rg->wq = devm_alloc_ordered_workqueue(dev, "panthor-%s-wq", WQ_FREEZABLE, name);
+	if (!rg->wq)
+		return -ENOMEM;
+
+	INIT_DELAYED_WORK(&rg->msg_retry_work, rg_retry_messages);
+
+	for (int i = 0; i < AM_ARB_MAX_AW_COUNT; i++)
+		panthor_am_msg_init(&rg->aw_data[i].msg,
+				    rg->iomem + AM_RG_AW_MESSAGE(i));
+
+	irq = platform_get_irq_byname(to_platform_device(dev), name);
+	if (irq < 0)
+		return irq;
+
+	rg->irq = irq;
+
+	irqdata = irq_get_irq_data(irq);
+	if (irqdata)
+		irq_flags = irqd_get_trigger_type(irqdata);
+
+	ret = devm_request_irq(
+		dev, irq, rg_irq_raw_handler, irq_flags | IRQF_SHARED,
+		devm_kasprintf(dev, GFP_KERNEL, "panthor-%s-irq", name), rg);
+	if (ret)
+		return ret;
+
+	adev->rg[i] = rg;
+
+	rg_irq_resume(rg);
+
+	rg_handshake_init(rg);
+
+	return 0;
+}
+
+int panthor_resource_group_init(struct panthor_arbitration *adev)
+{
+	for (int i = 0; i < AM_ARB_MAX_RG_COUNT; i++) {
+		int ret = resource_group_init(adev, i);
+
+		if (ret == -ENODEV)
+			continue;
+
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
diff --git a/drivers/gpu/drm/panthor/arbitration/panthor_resource_group.h b/drivers/gpu/drm/panthor/arbitration/panthor_resource_group.h
new file mode 100644
index 0000000000000..b8633abdd8eb8
--- /dev/null
+++ b/drivers/gpu/drm/panthor/arbitration/panthor_resource_group.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 or MIT */
+/* Copyright 2026 ARM Limited. All rights reserved. */
+
+#ifndef __PANTHOR_RESOURCE_GROUP_H__
+#define __PANTHOR_RESOURCE_GROUP_H__
+
+#include <linux/types.h>
+
+struct device;
+struct panthor_arbitration;
+
+int panthor_resource_group_init(struct panthor_arbitration *adev);
+
+void panthor_resource_group_term(struct panthor_arbitration *adev);
+
+int panthor_resource_group_suspend(struct panthor_arbitration *adev);
+
+int panthor_resource_group_resume(struct panthor_arbitration *adev);
+
+#endif
-- 
2.43.0