Re: [PATCH 03/15] accel/qda: Add initial QDA DRM accelerator driver

[Dmitry Baryshkov]

On Tue, May 19, 2026 at 11:45:53AM +0530, Ekansh Gupta via B4 Relay wrote:
> From: Ekansh Gupta <ekansh.gupta@xxxxxxxxxxxxxxxx>
> 
> Add the foundational driver files for the Qualcomm DSP Accelerator
> (QDA), a DRM accel driver for Qualcomm DSPs. The driver integrates
> with the DRM accel subsystem (drivers/accel/) and provides:
> 
>   - A standard /dev/accel/accel* character device node via DRM.
>   - GEM-based buffer management with DMA-BUF import/export (PRIME).
>   - IOMMU context bank management for per-session memory isolation.
>   - Standard DRM IOCTLs for device management and job submission.
> 
> qda_drv.c / qda_drv.h: Core DRM driver registration. Defines the
> drm_driver ops table, per-file private state (qda_file_priv), and the
> main device structure (qda_dev) which embeds drm_device.
> 
> qda_rpmsg.c / qda_rpmsg.h: RPMsg transport layer. Registers an
> rpmsg_driver matching the "qcom,fastrpc" compatible string. On probe
> it allocates a qda_dev, reads the DSP domain name from the "label" DT
> property, and registers the DRM device.
> 
> Assisted-by: Claude:claude-4-6-sonnet
> Signed-off-by: Ekansh Gupta <ekansh.gupta@xxxxxxxxxxxxxxxx>
> ---
>  drivers/accel/Kconfig         |  1 +
>  drivers/accel/Makefile        |  1 +
>  drivers/accel/qda/Kconfig     | 30 +++++++++++++
>  drivers/accel/qda/Makefile    | 10 +++++
>  drivers/accel/qda/qda_drv.c   | 97 ++++++++++++++++++++++++++++++++++++++++++
>  drivers/accel/qda/qda_drv.h   | 62 +++++++++++++++++++++++++++
>  drivers/accel/qda/qda_rpmsg.c | 99 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/accel/qda/qda_rpmsg.h | 13 ++++++
>  8 files changed, 313 insertions(+)
> 
> diff --git a/drivers/accel/Kconfig b/drivers/accel/Kconfig
> index bdf48ccafcf2..74ac0f71bc9d 100644
> --- a/drivers/accel/Kconfig
> +++ b/drivers/accel/Kconfig
> @@ -29,6 +29,7 @@ source "drivers/accel/ethosu/Kconfig"
>  source "drivers/accel/habanalabs/Kconfig"
>  source "drivers/accel/ivpu/Kconfig"
>  source "drivers/accel/qaic/Kconfig"
> +source "drivers/accel/qda/Kconfig"
>  source "drivers/accel/rocket/Kconfig"
>  
>  endif
> diff --git a/drivers/accel/Makefile b/drivers/accel/Makefile
> index 1d3a7251b950..58c08dd5f389 100644
> --- a/drivers/accel/Makefile
> +++ b/drivers/accel/Makefile
> @@ -5,4 +5,5 @@ obj-$(CONFIG_DRM_ACCEL_ARM_ETHOSU)	+= ethosu/
>  obj-$(CONFIG_DRM_ACCEL_HABANALABS)	+= habanalabs/
>  obj-$(CONFIG_DRM_ACCEL_IVPU)		+= ivpu/
>  obj-$(CONFIG_DRM_ACCEL_QAIC)		+= qaic/
> +obj-$(CONFIG_DRM_ACCEL_QDA)		+= qda/
>  obj-$(CONFIG_DRM_ACCEL_ROCKET)		+= rocket/
> \ No newline at end of file
> diff --git a/drivers/accel/qda/Kconfig b/drivers/accel/qda/Kconfig
> new file mode 100644
> index 000000000000..484d21ff1b55
> --- /dev/null
> +++ b/drivers/accel/qda/Kconfig
> @@ -0,0 +1,30 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +#
> +# Qualcomm DSP accelerator driver
> +#
> +
> +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
> +	  tasks to the DSP, including audio processing, sensor offload, computer
> +	  vision, and AI inference workloads.
> +
> +	  The driver supports all DSP domains (ADSP, CDSP, SDSP, GDSP) and
> +	  implements the FastRPC protocol for communication between the application
> +	  processor and DSP. It integrates with the Linux kernel's Compute
> +	  Accelerators subsystem (drivers/accel/) and provides a modern alternative
> +	  to the legacy FastRPC driver found in drivers/misc/.
> +
> +	  Key features include DMA-BUF interoperability for seamless buffer sharing

Key features of what? Consider distro maintainers reading your help text
in order to identify whether to enable it or not.

> +	  with other multimedia subsystems, IOMMU-based memory isolation, and
> +	  standard DRM IOCTLs for device management and job submission.
> +
> +	  If unsure, say N.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called qda.
> diff --git a/drivers/accel/qda/Makefile b/drivers/accel/qda/Makefile
> new file mode 100644
> index 000000000000..dbe809067a8b
> --- /dev/null
> +++ b/drivers/accel/qda/Makefile
> @@ -0,0 +1,10 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +#
> +# Makefile for Qualcomm DSP accelerator driver
> +#
> +
> +obj-$(CONFIG_DRM_ACCEL_QDA)	:= qda.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
> new file mode 100644
> index 000000000000..1c1bab68d445
> --- /dev/null
> +++ b/drivers/accel/qda/qda_drv.c
> @@ -0,0 +1,97 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <drm/drm_accel.h>
> +#include <drm/drm_drv.h>
> +#include <drm/drm_file.h>
> +#include <drm/drm_gem.h>
> +#include <drm/drm_ioctl.h>
> +#include <drm/drm_print.h>
> +
> +#include "qda_drv.h"
> +#include "qda_rpmsg.h"
> +
> +static int qda_open(struct drm_device *dev, struct drm_file *file)
> +{
> +	struct qda_file_priv *qda_file_priv;
> +
> +	qda_file_priv = kzalloc_obj(*qda_file_priv);
> +	if (!qda_file_priv)
> +		return -ENOMEM;
> +
> +	qda_file_priv->qda_dev = qda_dev_from_drm(dev);
> +	file->driver_priv = qda_file_priv;
> +
> +	return 0;
> +}
> +
> +static void qda_postclose(struct drm_device *dev, struct drm_file *file)
> +{
> +	struct qda_file_priv *qda_file_priv = file->driver_priv;
> +
> +	kfree(qda_file_priv);
> +	file->driver_priv = NULL;
> +}
> +
> +DEFINE_DRM_ACCEL_FOPS(qda_accel_fops);
> +
> +static const struct drm_driver qda_drm_driver = {
> +	.driver_features = DRIVER_COMPUTE_ACCEL,
> +	.fops = &qda_accel_fops,
> +	.open = qda_open,
> +	.postclose = qda_postclose,
> +	.name = QDA_DRIVER_NAME,
> +	.desc = "Qualcomm DSP Accelerator Driver",
> +};
> +
> +struct qda_dev *qda_alloc_device(struct device *dev)
> +{
> +	struct qda_dev *qdev;
> +
> +	qdev = devm_drm_dev_alloc(dev, &qda_drm_driver, struct qda_dev, drm_dev);
> +	if (IS_ERR(qdev))
> +		return ERR_CAST(qdev);
> +
> +	return qdev;
> +}
> +
> +void qda_unregister_device(struct qda_dev *qdev)
> +{
> +	drm_dev_unregister(&qdev->drm_dev);
> +}
> +
> +int qda_register_device(struct qda_dev *qdev)
> +{
> +	int ret;
> +
> +	ret = drm_dev_register(&qdev->drm_dev, 0);
> +	if (ret)
> +		drm_err(&qdev->drm_dev, "Failed to register DRM device: %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static int __init qda_core_init(void)
> +{
> +	int ret;
> +
> +	ret = qda_rpmsg_register();
> +	if (ret)
> +		return ret;
> +
> +	pr_info("qda: QDA driver initialization complete\n");
> +	return 0;
> +}
> +
> +static void __exit qda_core_exit(void)
> +{
> +	qda_rpmsg_unregister();
> +}
> +
> +module_init(qda_core_init);
> +module_exit(qda_core_exit);
> +
> +MODULE_AUTHOR("Qualcomm AI Infra Team");
> +MODULE_DESCRIPTION("Qualcomm DSP Accelerator Driver");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/accel/qda/qda_drv.h b/drivers/accel/qda/qda_drv.h
> new file mode 100644
> index 000000000000..7ba2ef19a411
> --- /dev/null
> +++ b/drivers/accel/qda/qda_drv.h
> @@ -0,0 +1,62 @@
> +/* 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/rpmsg.h>
> +#include <linux/types.h>
> +#include <drm/drm_device.h>
> +#include <drm/drm_drv.h>
> +#include <drm/drm_file.h>
> +
> +/* Driver identification */
> +#define QDA_DRIVER_NAME "qda"
> +
> +/**
> + * struct qda_file_priv - Per-process private data for DRM file
> + */
> +struct qda_file_priv {
> +	/** @qda_dev: Back-pointer to device structure */
> +	struct qda_dev *qda_dev;
> +};
> +
> +/**
> + * struct qda_dev - Main device structure for QDA driver
> + *
> + * The DRM device is embedded as the first member so that container_of()
> + * can recover the qda_dev from any drm_device pointer.
> + */
> +struct qda_dev {
> +	/** @drm_dev: Embedded DRM device; recover via qda_dev_from_drm() */
> +	struct drm_device drm_dev;
> +	/** @rpdev: RPMsg device for communication with the remote processor */
> +	struct rpmsg_device *rpdev;
> +	/** @dev: Underlying Linux device */
> +	struct device *dev;
> +	/** @dsp_name: Name of the DSP domain (e.g. "cdsp", "adsp") */
> +	const char *dsp_name;
> +};
> +
> +/**
> + * qda_dev_from_drm - Recover qda_dev from an embedded drm_device pointer
> + * @dev: Pointer to the embedded drm_device
> + *
> + * Return: Pointer to the enclosing qda_dev.
> + */
> +static inline struct qda_dev *qda_dev_from_drm(struct drm_device *dev)
> +{
> +	return container_of(dev, struct qda_dev, drm_dev);
> +}
> +
> +/* Device allocation (uses devm_drm_dev_alloc internally) */
> +struct qda_dev *qda_alloc_device(struct device *dev);
> +
> +/* Core device lifecycle */
> +int qda_register_device(struct qda_dev *qdev);
> +void qda_unregister_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..6eaf1b145f8a
> --- /dev/null
> +++ b/drivers/accel/qda/qda_rpmsg.c
> @@ -0,0 +1,99 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/rpmsg.h>
> +#include <drm/drm_print.h>
> +
> +#include "qda_drv.h"
> +#include "qda_rpmsg.h"
> +
> +static struct qda_dev *alloc_and_init_qdev(struct rpmsg_device *rpdev)

Use the prefix uniformly.

> +{
> +	struct qda_dev *qdev;
> +
> +	qdev = qda_alloc_device(&rpdev->dev);
> +	if (IS_ERR(qdev))
> +		return qdev;
> +
> +	qdev->dev = &rpdev->dev;
> +	qdev->rpdev = rpdev;
> +	dev_set_drvdata(&rpdev->dev, qdev);
> +
> +	return qdev;
> +}
> +
> +static int qda_rpmsg_cb(struct rpmsg_device *rpdev, void *data, int len,
> +			void *priv, u32 src)
> +{
> +	/* Placeholder: responses will be dispatched here */
> +	return 0;
> +}
> +
> +static void qda_rpmsg_remove(struct rpmsg_device *rpdev)
> +{
> +	struct qda_dev *qdev = dev_get_drvdata(&rpdev->dev);
> +
> +	drm_dev_unplug(&qdev->drm_dev);
> +	qdev->rpdev = NULL;
> +	qda_unregister_device(qdev);
> +	dev_info(qdev->dev, "RPMsg device removed\n");

Drop the spamming. And useless (where it is useless) drm_dbg() / dev_dbg() spamming too.

> +}
> +
> +static int qda_rpmsg_probe(struct rpmsg_device *rpdev)
> +{
> +	struct qda_dev *qdev;
> +	const char *label;
> +	int ret;
> +
> +	dev_dbg(&rpdev->dev, "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) {
> +		dev_err(qdev->dev, "Missing 'label' property in DT node: %d\n", ret);
> +		return ret;
> +	}
> +	qdev->dsp_name = label;

Why not just of_property_read_string(...., &qdev->dsp_name)?

> +
> +	ret = qda_register_device(qdev);

return qda_register_device();

> +	if (ret)
> +		return ret;
> +
> +	drm_info(&qdev->drm_dev, "QDA RPMsg probe complete 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)
> +		pr_err("qda: Failed to register RPMsg driver: %d\n", ret);
> +
> +	return ret;
> +}
> +
> +void qda_rpmsg_unregister(void)
> +{
> +	unregister_rpmsg_driver(&qda_rpmsg_driver);
> +}

Just use module_rpmsg_driver(), drop all the wrappers and module_init()
/ exit().

> diff --git a/drivers/accel/qda/qda_rpmsg.h b/drivers/accel/qda/qda_rpmsg.h
> new file mode 100644
> index 000000000000..5229d834b34b
> --- /dev/null
> +++ b/drivers/accel/qda/qda_rpmsg.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + */
> +
> +#ifndef __QDA_RPMSG_H__
> +#define __QDA_RPMSG_H__
> +
> +/* RPMsg transport layer registration */
> +int qda_rpmsg_register(void);
> +void qda_rpmsg_unregister(void);
> +
> +#endif /* __QDA_RPMSG_H__ */
> 
> -- 
> 2.34.1
> 
> 

-- 
With best wishes
Dmitry