From: Ekansh Gupta <[email protected]> Introduce a custom virtual bus (qda-compute-cb) for managing IOMMU context bank (CB) devices used by the QDA driver.
IOMMU context banks are synthetic constructs — they are not real platform devices and do not appear as children of a platform bus node in the device tree. Using a platform driver to represent them was therefore incorrect and introduced a probe-ordering race: device nodes were created before the RPMsg channel resources were fully initialized, and because probe runs asynchronously, user-space could open a CB device and attempt to start a session before the underlying transport was ready. The qda-compute-cb bus solves this by allowing the main QDA driver to create CB devices explicitly and under its own control, making their lifetime strictly subordinate to the parent qda_dev. The bus provides a dma_configure callback that calls of_dma_configure() so that each CB device gets its own IOMMU domain derived from its device-tree node, enabling per-session memory isolation. The bus type and the CB device constructor (create_qda_cb_device) are exported for use by the QDA memory manager. A hidden Kconfig symbol (DRM_ACCEL_QDA_COMPUTE_BUS) is introduced and automatically selected by DRM_ACCEL_QDA so that the bus initialisation runs via postcore_initcall before any QDA device probes. Assisted-by: Claude:claude-4-6-sonnet Signed-off-by: Ekansh Gupta <[email protected]> --- drivers/accel/Makefile | 1 + drivers/accel/qda/Kconfig | 4 +++ drivers/accel/qda/Makefile | 2 ++ drivers/accel/qda/qda_compute_bus.c | 68 +++++++++++++++++++++++++++++++++++++ include/linux/qda_compute_bus.h | 32 +++++++++++++++++ 5 files changed, 107 insertions(+) diff --git a/drivers/accel/Makefile b/drivers/accel/Makefile index 58c08dd5f389..9ed843cd293f 100644 --- a/drivers/accel/Makefile +++ b/drivers/accel/Makefile @@ -6,4 +6,5 @@ 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-$(CONFIG_DRM_ACCEL_QDA_COMPUTE_BUS) += qda/ obj-$(CONFIG_DRM_ACCEL_ROCKET) += rocket/ \ No newline at end of file diff --git a/drivers/accel/qda/Kconfig b/drivers/accel/qda/Kconfig index 484d21ff1b55..2a61a4dda054 100644 --- a/drivers/accel/qda/Kconfig +++ b/drivers/accel/qda/Kconfig @@ -3,11 +3,15 @@ # Qualcomm DSP accelerator driver # +config DRM_ACCEL_QDA_COMPUTE_BUS + bool + config DRM_ACCEL_QDA tristate "Qualcomm DSP accelerator" depends on DRM_ACCEL depends on ARCH_QCOM || COMPILE_TEST depends on RPMSG + select DRM_ACCEL_QDA_COMPUTE_BUS 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 dbe809067a8b..424176f652a5 100644 --- a/drivers/accel/qda/Makefile +++ b/drivers/accel/qda/Makefile @@ -8,3 +8,5 @@ obj-$(CONFIG_DRM_ACCEL_QDA) := qda.o qda-y := \ qda_drv.o \ qda_rpmsg.o + +obj-$(CONFIG_DRM_ACCEL_QDA_COMPUTE_BUS) += qda_compute_bus.o diff --git a/drivers/accel/qda/qda_compute_bus.c b/drivers/accel/qda/qda_compute_bus.c new file mode 100644 index 000000000000..c59d977e924d --- /dev/null +++ b/drivers/accel/qda/qda_compute_bus.c @@ -0,0 +1,68 @@ +// SPDX-License-Identifier: GPL-2.0-only +// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries. +#include <linux/device.h> +#include <linux/init.h> +#include <linux/of.h> +#include <linux/of_device.h> +#include <linux/qda_compute_bus.h> +#include <linux/slab.h> + +static int qda_cb_bus_dma_configure(struct device *dev) +{ + return of_dma_configure(dev, dev->of_node, true); +} + +const struct bus_type qda_cb_bus_type = { + .name = "qda-compute-cb", + .dma_configure = qda_cb_bus_dma_configure, +}; +EXPORT_SYMBOL_GPL(qda_cb_bus_type); + +static void release_qda_cb_device(struct device *dev) +{ + of_node_put(dev->of_node); + kfree(dev); +} + +struct device *create_qda_cb_device(struct device *parent_device, const char *name, + u64 dma_mask, struct device_node *of_node) +{ + struct device *dev; + int ret; + + dev = kzalloc_obj(*dev); + if (!dev) + return ERR_PTR(-ENOMEM); + + dev->release = release_qda_cb_device; + dev->bus = &qda_cb_bus_type; + dev->parent = parent_device; + dev->coherent_dma_mask = dma_mask; + dev->dma_mask = &dev->coherent_dma_mask; + dev->of_node = of_node_get(of_node); + + dev_set_name(dev, "%s", name); + + ret = device_register(dev); + if (ret) { + put_device(dev); + return ERR_PTR(ret); + } + + return dev; +} +EXPORT_SYMBOL_GPL(create_qda_cb_device); + +static int __init qda_cb_bus_init(void) +{ + int err; + + err = bus_register(&qda_cb_bus_type); + if (err < 0) { + pr_err("qda-compute-cb bus registration failed: %d\n", err); + return err; + } + return 0; +} + +postcore_initcall(qda_cb_bus_init); diff --git a/include/linux/qda_compute_bus.h b/include/linux/qda_compute_bus.h new file mode 100644 index 000000000000..90bf248c7285 --- /dev/null +++ b/include/linux/qda_compute_bus.h @@ -0,0 +1,32 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries. + */ + +#ifndef __QDA_COMPUTE_BUS_H__ +#define __QDA_COMPUTE_BUS_H__ + +#include <linux/device.h> + +/* + * Custom bus type for QDA compute context bank (CB) devices + * + * This bus type is used for manually created CB devices that represent + * IOMMU context banks. The custom bus allows proper IOMMU configuration + * and device management for these virtual devices. + */ +#ifdef CONFIG_DRM_ACCEL_QDA_COMPUTE_BUS +extern const struct bus_type qda_cb_bus_type; + +struct device *create_qda_cb_device(struct device *parent_device, const char *name, + u64 dma_mask, struct device_node *of_node); +#else +static inline struct device *create_qda_cb_device(struct device *parent_device, + const char *name, u64 dma_mask, + struct device_node *of_node) +{ + return ERR_PTR(-ENODEV); +} +#endif + +#endif /* __QDA_COMPUTE_BUS_H__ */ -- 2.34.1
