[PATCH RFC 03/18] accel/qda: Add RPMsg transport for Qualcomm DSP accelerator

[Ekansh Gupta]

Extend the Qualcomm DSP accelerator (QDA) driver with an RPMsg-based
transport used to discover and manage DSP instances.

This patch introduces:

- A core qda_dev structure with basic device state (rpmsg device,
  device pointer, lock, removal flag, DSP name).
- Logging helpers that integrate with dev_* when a device is available
  and fall back to pr_* otherwise.
- An RPMsg client driver that binds to the Qualcomm FastRPC service and
  allocates a qda_dev instance using devm_kzalloc().
- Basic device initialization and teardown paths wired into the module
  init/exit.

The RPMsg driver currently sets the DSP name from a "label" property in
the device tree, which will be used by subsequent patches to distinguish
between different DSP domains (e.g. ADSP, CDSP).

Signed-off-by: Ekansh Gupta <ekansh.gupta@xxxxxxxxxxxxxxxx>
---
 drivers/accel/qda/Kconfig     |   1 +
 drivers/accel/qda/Makefile    |   4 +-
 drivers/accel/qda/qda_drv.c   |  41 ++++++++++++++-
 drivers/accel/qda/qda_drv.h   |  91 ++++++++++++++++++++++++++++++++
 drivers/accel/qda/qda_rpmsg.c | 119 ++++++++++++++++++++++++++++++++++++++++++
 drivers/accel/qda/qda_rpmsg.h |  17 ++++++
 6 files changed, 270 insertions(+), 3 deletions(-)

diff --git a/drivers/accel/qda/Kconfig b/drivers/accel/qda/Kconfig
index 3c78ff6189e0..484d21ff1b55 100644
--- a/drivers/accel/qda/Kconfig
+++ b/drivers/accel/qda/Kconfig
@@ -7,6 +7,7 @@ config DRM_ACCEL_QDA
 	tristate "Qualcomm DSP accelerator"
 	depends on DRM_ACCEL
 	depends on ARCH_QCOM || COMPILE_TEST
+	depends on RPMSG
 	help
 	  Enables the DRM-based accelerator driver for Qualcomm's Hexagon DSPs.
 	  This driver provides a standardized interface for offloading computational
diff --git a/drivers/accel/qda/Makefile b/drivers/accel/qda/Makefile
index 573711af1d28..e7f23182589b 100644
--- a/drivers/accel/qda/Makefile
+++ b/drivers/accel/qda/Makefile
@@ -5,4 +5,6 @@
 
 obj-$(CONFIG_DRM_ACCEL_QDA)	:= qda.o
 
-qda-y := qda_drv.o
+qda-y := \
+	qda_drv.o \
+	qda_rpmsg.o \
diff --git a/drivers/accel/qda/qda_drv.c b/drivers/accel/qda/qda_drv.c
index 18b0d3fb1598..389c66a9ad4f 100644
--- a/drivers/accel/qda/qda_drv.c
+++ b/drivers/accel/qda/qda_drv.c
@@ -2,16 +2,53 @@
 // Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
 #include <linux/module.h>
 #include <linux/kernel.h>
+#include <linux/atomic.h>
+#include "qda_drv.h"
+#include "qda_rpmsg.h"
+
+static void cleanup_device_resources(struct qda_dev *qdev)
+{
+	mutex_destroy(&qdev->lock);
+}
+
+void qda_deinit_device(struct qda_dev *qdev)
+{
+	cleanup_device_resources(qdev);
+}
+
+/* Initialize device resources */
+static void init_device_resources(struct qda_dev *qdev)
+{
+	qda_dbg(qdev, "Initializing device resources\n");
+
+	mutex_init(&qdev->lock);
+	atomic_set(&qdev->removing, 0);
+}
+
+int qda_init_device(struct qda_dev *qdev)
+{
+	init_device_resources(qdev);
+
+	qda_dbg(qdev, "QDA device initialized successfully\n");
+	return 0;
+}
 
 static int __init qda_core_init(void)
 {
-	pr_info("QDA: driver initialization complete\n");
+	int ret;
+
+	ret = qda_rpmsg_register();
+	if (ret)
+		return ret;
+
+	qda_info(NULL, "QDA driver initialization complete\n");
 	return 0;
 }
 
 static void __exit qda_core_exit(void)
 {
-	pr_info("QDA: driver exit complete\n");
+	qda_rpmsg_unregister();
+	qda_info(NULL, "QDA driver exit complete\n");
 }
 
 module_init(qda_core_init);
diff --git a/drivers/accel/qda/qda_drv.h b/drivers/accel/qda/qda_drv.h
new file mode 100644
index 000000000000..bec2d31ca1bb
--- /dev/null
+++ b/drivers/accel/qda/qda_drv.h
@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+
+#ifndef __QDA_DRV_H__
+#define __QDA_DRV_H__
+
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/rpmsg.h>
+#include <linux/xarray.h>
+
+/* Driver identification */
+#define DRIVER_NAME "qda"
+
+/* struct qda_dev - Main device structure for QDA driver */
+struct qda_dev {
+	/* RPMsg device for communication with remote processor */
+	struct rpmsg_device *rpdev;
+	/* Underlying device structure */
+	struct device *dev;
+	/* Mutex protecting device state */
+	struct mutex lock;
+	/* Flag indicating device removal in progress */
+	atomic_t removing;
+	/* Name of the DSP (e.g., "cdsp", "adsp") */
+	char dsp_name[16];
+};
+
+/**
+ * qda_get_log_device - Get appropriate device for logging
+ * @qdev: QDA device structure
+ *
+ * Returns the most appropriate device structure for logging messages.
+ * Prefers qdev->dev, or returns NULL if the device is being removed
+ * or invalid.
+ */
+static inline struct device *qda_get_log_device(struct qda_dev *qdev)
+{
+	if (!qdev || atomic_read(&qdev->removing))
+		return NULL;
+
+	if (qdev->dev)
+		return qdev->dev;
+
+	return NULL;
+}
+
+/*
+ * Logging macros
+ *
+ * These macros provide consistent logging across the driver with automatic
+ * function name inclusion. They use dev_* functions when a device is available,
+ * falling back to pr_* functions otherwise.
+ */
+
+/* Error logging - always logs and tracks errors */
+#define qda_err(qdev, fmt, ...) do { \
+	struct device *__dev = qda_get_log_device(qdev); \
+	if (__dev) \
+		dev_err(__dev, "[%s] " fmt, __func__, ##__VA_ARGS__); \
+	else \
+		pr_err(DRIVER_NAME ": [%s] " fmt, __func__, ##__VA_ARGS__); \
+} while (0)
+
+/* Info logging - always logs, can be filtered via loglevel */
+#define qda_info(qdev, fmt, ...) do { \
+	struct device *__dev = qda_get_log_device(qdev); \
+	if (__dev) \
+		dev_info(__dev, "[%s] " fmt, __func__, ##__VA_ARGS__); \
+	else \
+		pr_info(DRIVER_NAME ": [%s] " fmt, __func__, ##__VA_ARGS__); \
+} while (0)
+
+/* Debug logging - controlled via dynamic debug (CONFIG_DYNAMIC_DEBUG) */
+#define qda_dbg(qdev, fmt, ...) do { \
+	struct device *__dev = qda_get_log_device(qdev); \
+	if (__dev) \
+		dev_dbg(__dev, "[%s] " fmt, __func__, ##__VA_ARGS__); \
+	else \
+		pr_debug(DRIVER_NAME ": [%s] " fmt, __func__, ##__VA_ARGS__); \
+} while (0)
+
+/*
+ * Core device management functions
+ */
+int qda_init_device(struct qda_dev *qdev);
+void qda_deinit_device(struct qda_dev *qdev);
+
+#endif /* __QDA_DRV_H__ */
diff --git a/drivers/accel/qda/qda_rpmsg.c b/drivers/accel/qda/qda_rpmsg.c
new file mode 100644
index 000000000000..a8b24a99ca13
--- /dev/null
+++ b/drivers/accel/qda/qda_rpmsg.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+#include <linux/module.h>
+#include <linux/rpmsg.h>
+#include <linux/of_platform.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include "qda_drv.h"
+#include "qda_rpmsg.h"
+
+static int qda_rpmsg_init(struct qda_dev *qdev)
+{
+	dev_set_drvdata(&qdev->rpdev->dev, qdev);
+	return 0;
+}
+
+/* Utility function to allocate and initialize qda_dev */
+static struct qda_dev *alloc_and_init_qdev(struct rpmsg_device *rpdev)
+{
+	struct qda_dev *qdev;
+
+	qdev = devm_kzalloc(&rpdev->dev, sizeof(*qdev), GFP_KERNEL);
+	if (!qdev)
+		return ERR_PTR(-ENOMEM);
+
+	qdev->dev = &rpdev->dev;
+	qdev->rpdev = rpdev;
+
+	qda_dbg(qdev, "Allocated and initialized qda_dev\n");
+	return qdev;
+}
+
+static int qda_rpmsg_cb(struct rpmsg_device *rpdev, void *data, int len, void *priv, u32 src)
+{
+	/* Dummy function for rpmsg driver */
+	return 0;
+}
+
+static void qda_rpmsg_remove(struct rpmsg_device *rpdev)
+{
+	struct qda_dev *qdev = dev_get_drvdata(&rpdev->dev);
+
+	qda_info(qdev, "Removing RPMsg device\n");
+
+	atomic_set(&qdev->removing, 1);
+
+	mutex_lock(&qdev->lock);
+	qdev->rpdev = NULL;
+	mutex_unlock(&qdev->lock);
+
+	qda_deinit_device(qdev);
+
+	qda_info(qdev, "RPMsg device removed\n");
+}
+
+static int qda_rpmsg_probe(struct rpmsg_device *rpdev)
+{
+	struct qda_dev *qdev;
+	int ret;
+	const char *label;
+
+	qda_dbg(NULL, "QDA RPMsg probe starting\n");
+
+	qdev = alloc_and_init_qdev(rpdev);
+	if (IS_ERR(qdev))
+		return PTR_ERR(qdev);
+
+	ret = of_property_read_string(rpdev->dev.of_node, "label", &label);
+	if (!ret) {
+		strscpy(qdev->dsp_name, label, sizeof(qdev->dsp_name));
+	} else {
+		qda_info(qdev, "QDA DSP label not found in DT\n");
+		return ret;
+	}
+
+	ret = qda_rpmsg_init(qdev);
+	if (ret) {
+		qda_err(qdev, "RPMsg init failed: %d\n", ret);
+		return ret;
+	}
+
+	ret = qda_init_device(qdev);
+	if (ret)
+		return ret;
+
+	qda_info(qdev, "QDA RPMsg probe completed successfully for %s\n", qdev->dsp_name);
+	return 0;
+}
+
+static const struct of_device_id qda_rpmsg_id_table[] = {
+	{ .compatible = "qcom,fastrpc" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, qda_rpmsg_id_table);
+
+static struct rpmsg_driver qda_rpmsg_driver = {
+	.probe = qda_rpmsg_probe,
+	.remove = qda_rpmsg_remove,
+	.callback = qda_rpmsg_cb,
+	.drv = {
+		.name = "qcom,fastrpc",
+		.of_match_table = qda_rpmsg_id_table,
+	},
+};
+
+int qda_rpmsg_register(void)
+{
+	int ret = register_rpmsg_driver(&qda_rpmsg_driver);
+
+	if (ret)
+		qda_err(NULL, "Failed to register RPMsg driver: %d\n", ret);
+
+	return ret;
+}
+
+void qda_rpmsg_unregister(void)
+{
+	unregister_rpmsg_driver(&qda_rpmsg_driver);
+}
diff --git a/drivers/accel/qda/qda_rpmsg.h b/drivers/accel/qda/qda_rpmsg.h
new file mode 100644
index 000000000000..348827bff255
--- /dev/null
+++ b/drivers/accel/qda/qda_rpmsg.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+
+#ifndef __QDA_RPMSG_H__
+#define __QDA_RPMSG_H__
+
+#include "qda_drv.h"
+
+/*
+ * Transport layer registration
+ */
+int qda_rpmsg_register(void);
+void qda_rpmsg_unregister(void);
+
+#endif /* __QDA_RPMSG_H__ */

-- 
2.34.1