accel/qaic: Add DMA Bridge Channel(DBC) sysfs and uevents

Expose sysfs files for each DBC representing the current state of that DBC.
For example, sysfs for DBC ID 0 and accel minor number 0 looks like this,

/sys/class/accel/accel0/dbc0_state

Following are the states and their corresponding values,
DBC_STATE_IDLE (0)
DBC_STATE_ASSIGNED (1)
DBC_STATE_BEFORE_SHUTDOWN (2)
DBC_STATE_AFTER_SHUTDOWN (3)
DBC_STATE_BEFORE_POWER_UP (4)
DBC_STATE_AFTER_POWER_UP (5)

Signed-off-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@quicinc.com>
Signed-off-by: Youssef Samir <youssef.abdulrahman@oss.qualcomm.com>
Signed-off-by: Zack McKevitt <zachary.mckevitt@oss.qualcomm.com>
Reviewed-by: Jeff Hugo <jeff.hugo@oss.qualcomm.com>
Signed-off-by: Jeff Hugo <jeff.hugo@oss.qualcomm.com>
Link: https://patch.msgid.link/20251031174059.2814445-2-zachary.mckevitt@oss.qualcomm.com

Documentation/ABI/stable/sysfs-driver-qaic

@@ -0,0 +1,16 @@
+What:		/sys/bus/pci/drivers/qaic/XXXX:XX:XX.X/accel/accel<minor_nr>/dbc<N>_state
+Date:		October 2025
+KernelVersion:	6.19
+Contact:	Jeff Hugo <jeff.hugo@oss.qualcomm.com>
+Description:	Represents the current state of DMA Bridge channel (DBC). Below are the possible
+		states,
+		IDLE (0) -		DBC is free and can be activated
+		ASSIGNED (1) -		DBC is activated and a workload is running on device
+		BEFORE_SHUTDOWN (2) -	Sub-system associated with this workload has crashed and
+					it will shutdown soon
+		AFTER_SHUTDOWN (3) -	Sub-system associated with this workload has crashed and
+					it has shutdown
+		BEFORE_POWER_UP (4) -	Sub-system associated with this workload is shutdown and
+					it will be powered up soon
+		AFTER_POWER_UP (5) -	Sub-system associated with this workload is now powered up
+Users:		Any userspace application or clients interested in DBC state.

drivers/accel/qaic/Makefile

@@ -11,6 +11,7 @@ qaic-y := \
 	qaic_data.o \
 	qaic_drv.o \
 	qaic_ras.o \
+	qaic_sysfs.o \
 	qaic_timesync.o \
 	sahara.o
 

drivers/accel/qaic/qaic.h

@@ -47,6 +47,22 @@ enum __packed dev_states {
 	QAIC_ONLINE,
 };
 
+enum dbc_states {
+	/* DBC is free and can be activated */
+	DBC_STATE_IDLE,
+	/* DBC is activated and a workload is running on device */
+	DBC_STATE_ASSIGNED,
+	/* Sub-system associated with this workload has crashed and it will shutdown soon */
+	DBC_STATE_BEFORE_SHUTDOWN,
+	/* Sub-system associated with this workload has crashed and it has shutdown */
+	DBC_STATE_AFTER_SHUTDOWN,
+	/* Sub-system associated with this workload is shutdown and it will be powered up soon */
+	DBC_STATE_BEFORE_POWER_UP,
+	/* Sub-system associated with this workload is now powered up */
+	DBC_STATE_AFTER_POWER_UP,
+	DBC_STATE_MAX,
+};
+
 extern bool datapath_polling;
 
 struct qaic_user {
@@ -114,6 +130,8 @@ struct dma_bridge_chan {
 	unsigned int		irq;
 	/* Polling work item to simulate interrupts */
 	struct work_struct	poll_work;
+	/* Represents various states of this DBC from enum dbc_states */
+	unsigned int		state;
 };
 
 struct qaic_device {
@@ -197,6 +215,8 @@ struct qaic_drm_device {
 	struct list_head	users;
 	/* Synchronizes access to users list */
 	struct mutex		users_mutex;
+	/* Pointer to array of DBC sysfs attributes */
+	void			*sysfs_attrs;
 };
 
 struct qaic_bo {
@@ -321,4 +341,9 @@ int qaic_perf_stats_bo_ioctl(struct drm_device *dev, void *data, struct drm_file
 int qaic_detach_slice_bo_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv);
 void irq_polling_work(struct work_struct *work);
 
+/* qaic_sysfs.c */
+int qaic_sysfs_init(struct qaic_drm_device *qddev);
+void qaic_sysfs_remove(struct qaic_drm_device *qddev);
+void set_dbc_state(struct qaic_device *qdev, u32 dbc_id, unsigned int state);
+
 #endif /* _QAIC_H_ */

drivers/accel/qaic/qaic_control.c

@@ -310,6 +310,7 @@ static void save_dbc_buf(struct qaic_device *qdev, struct ioctl_resources *resou
 		enable_dbc(qdev, dbc_id, usr);
 		qdev->dbc[dbc_id].in_use = true;
 		resources->buf = NULL;
+		set_dbc_state(qdev, dbc_id, DBC_STATE_ASSIGNED);
 	}
 }
 
@@ -923,6 +924,7 @@ static int decode_deactivate(struct qaic_device *qdev, void *trans, u32 *msg_len
 	}
 
 	release_dbc(qdev, dbc_id);
+	set_dbc_state(qdev, dbc_id, DBC_STATE_IDLE);
 	*msg_len += sizeof(*in_trans);
 
 	return 0;

drivers/accel/qaic/qaic_drv.c

@@ -270,6 +270,13 @@ static int qaic_create_drm_device(struct qaic_device *qdev, s32 partition_id)
 		return ret;
 	}
 
+	ret = qaic_sysfs_init(qddev);
+	if (ret) {
+		drm_dev_unregister(drm);
+		pci_dbg(qdev->pdev, "qaic_sysfs_init failed %d\n", ret);
+		return ret;
+	}
+
 	qaic_debugfs_init(qddev);
 
 	return ret;
@@ -281,6 +288,7 @@ static void qaic_destroy_drm_device(struct qaic_device *qdev, s32 partition_id)
 	struct drm_device *drm = to_drm(qddev);
 	struct qaic_user *usr;
 
+	qaic_sysfs_remove(qddev);
 	drm_dev_unregister(drm);
 	qddev->partition_id = 0;
 	/*

drivers/accel/qaic/qaic_sysfs.c

@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/* Copyright (c) 2020-2025, The Linux Foundation. All rights reserved. */
+
+#include <drm/drm_file.h>
+#include <drm/drm_managed.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/kobject.h>
+#include <linux/mutex.h>
+#include <linux/sysfs.h>
+
+#include "qaic.h"
+
+#define NAME_LEN		14
+
+struct dbc_attribute {
+	struct device_attribute dev_attr;
+	u32 dbc_id;
+	char name[NAME_LEN];
+};
+
+static ssize_t dbc_state_show(struct device *dev, struct device_attribute *a, char *buf)
+{
+	struct dbc_attribute *dbc_attr = container_of(a, struct dbc_attribute, dev_attr);
+	struct drm_minor *minor = dev_get_drvdata(dev);
+	struct qaic_device *qdev;
+
+	qdev = to_qaic_device(minor->dev);
+	return sysfs_emit(buf, "%d\n", qdev->dbc[dbc_attr->dbc_id].state);
+}
+
+void set_dbc_state(struct qaic_device *qdev, u32 dbc_id, unsigned int state)
+{
+	struct device *kdev = to_accel_kdev(qdev->qddev);
+	char *envp[3] = {};
+	char state_str[16];
+	char id_str[12];
+
+	envp[0] = id_str;
+	envp[1] = state_str;
+
+	if (state >= DBC_STATE_MAX)
+		return;
+	if (dbc_id >= qdev->num_dbc)
+		return;
+	if (state == qdev->dbc[dbc_id].state)
+		return;
+
+	scnprintf(id_str, ARRAY_SIZE(id_str), "DBC_ID=%d", dbc_id);
+	scnprintf(state_str, ARRAY_SIZE(state_str), "DBC_STATE=%d", state);
+
+	qdev->dbc[dbc_id].state = state;
+	kobject_uevent_env(&kdev->kobj, KOBJ_CHANGE, envp);
+}
+
+int qaic_sysfs_init(struct qaic_drm_device *qddev)
+{
+	struct device *kdev = to_accel_kdev(qddev);
+	struct drm_device *drm = to_drm(qddev);
+	u32 num_dbc = qddev->qdev->num_dbc;
+	struct dbc_attribute *dbc_attrs;
+	int i, ret;
+
+	dbc_attrs = drmm_kcalloc(drm, num_dbc, sizeof(*dbc_attrs), GFP_KERNEL);
+	if (!dbc_attrs)
+		return -ENOMEM;
+
+	for (i = 0; i < num_dbc; ++i) {
+		struct dbc_attribute *dbc_attr = &dbc_attrs[i];
+
+		sysfs_attr_init(&dbc_attr->dev_attr.attr);
+		dbc_attr->dbc_id = i;
+		scnprintf(dbc_attr->name, NAME_LEN, "dbc%d_state", i);
+		dbc_attr->dev_attr.attr.name = dbc_attr->name;
+		dbc_attr->dev_attr.attr.mode = 0444;
+		dbc_attr->dev_attr.show = dbc_state_show;
+		ret = sysfs_create_file(&kdev->kobj, &dbc_attr->dev_attr.attr);
+		if (ret) {
+			int j;
+
+			for (j = 0; j < i; ++j) {
+				dbc_attr = &dbc_attrs[j];
+				sysfs_remove_file(&kdev->kobj, &dbc_attr->dev_attr.attr);
+			}
+			drmm_kfree(drm, dbc_attrs);
+			return ret;
+		}
+	}
+
+	qddev->sysfs_attrs = dbc_attrs;
+	return 0;
+}
+
+void qaic_sysfs_remove(struct qaic_drm_device *qddev)
+{
+	struct dbc_attribute *dbc_attrs = qddev->sysfs_attrs;
+	struct device *kdev = to_accel_kdev(qddev);
+	u32 num_dbc = qddev->qdev->num_dbc;
+	int i;
+
+	if (!dbc_attrs)
+		return;
+
+	qddev->sysfs_attrs = NULL;
+	for (i = 0; i < num_dbc; ++i)
+		sysfs_remove_file(&kdev->kobj, &dbc_attrs[i].dev_attr.attr);
+	drmm_kfree(to_drm(qddev), dbc_attrs);
+}