Re: [PATCH v16 2/7] qcom-tgu: Add TGU driver

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 30/07/2026 09:06, Songwei Chai wrote:
> Add driver to support device TGU (Trigger Generation Unit).
> TGU is a Data Engine which can be utilized to sense a plurality of
> signals and create a trigger into the CTI or generate interrupts to
> processors. Add probe/enable/disable functions for tgu.
> 
> Signed-off-by: Songwei Chai <songwei.chai@oss.qualcomm.com>
> Acked-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> Reviewed-by: Jie Gan <jie.gan@oss.qualcomm.com>
> ---
>   .../ABI/testing/sysfs-bus-amba-devices-tgu    |   9 +
>   MAINTAINERS                                   |  11 +
>   drivers/Makefile                              |   1 +
>   drivers/hwtracing/Kconfig                     |   2 +
>   drivers/hwtracing/qcom/Kconfig                |  20 ++
>   drivers/hwtracing/qcom/Makefile               |   3 +
>   drivers/hwtracing/qcom/tgu.c                  | 192 ++++++++++++++++++
>   drivers/hwtracing/qcom/tgu.h                  |  51 +++++
>   8 files changed, 289 insertions(+)
>   create mode 100644 Documentation/ABI/testing/sysfs-bus-amba-devices-tgu
>   create mode 100644 drivers/hwtracing/qcom/Kconfig
>   create mode 100644 drivers/hwtracing/qcom/Makefile
>   create mode 100644 drivers/hwtracing/qcom/tgu.c
>   create mode 100644 drivers/hwtracing/qcom/tgu.h
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-amba-devices-tgu b/Documentation/ABI/testing/sysfs-bus-amba-devices-tgu
> new file mode 100644
> index 000000000000..36ab64f1e301
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-amba-devices-tgu
> @@ -0,0 +1,9 @@
> +What:		/sys/bus/amba/devices/<tgu-name>/enable_tgu
> +Date:		August 2026
> +KernelVersion:	7.2
> +Contact:	Jinlong Mao <jinlong.mao@oss.qualcomm.com>, Songwei Chai <songwei.chai@oss.qualcomm.com>
> +Description:
> +		(RW) Set/Get the enable/disable status of TGU
> +		Accepts only one of the 2 values -  0 or 1.
> +		0 : disable TGU.
> +		1 : enable TGU.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index ce5c5185c773..4789321cca6d 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -22360,6 +22360,17 @@ S:	Maintained
>   F:	Documentation/tee/qtee.rst
>   F:	drivers/tee/qcomtee/
>   
> +QUALCOMM HARDWARETRACING DRIVER
> +M:	Songwei Chai <songwei.chai@oss.qualcomm.com>
> +M:	Jie Gan <jie.gan@oss.qualcomm.com>
> +M:	Suzuki K Poulose <suzuki.poulose@arm.com>
> +L:	linux-arm-msm@vger.kernel.org
> +S:	Maintained
> +T:	git git://git.kernel.org/pub/scm/linux/kernel/git/coresight/linux.git
> +F:	Documentation/ABI/testing/sysfs-bus-amba-devices-tgu
> +F:	Documentation/devicetree/bindings/arm/qcom,tgu.yaml
> +F:	drivers/hwtracing/qcom/
> +
>   QUALCOMM TRUST ZONE MEMORY ALLOCATOR
>   M:	Bartosz Golaszewski <brgl@kernel.org>
>   L:	linux-arm-msm@vger.kernel.org
> diff --git a/drivers/Makefile b/drivers/Makefile
> index 0841ea851847..6a2cbe5b340f 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -176,6 +176,7 @@ obj-$(CONFIG_RAS)		+= ras/
>   obj-$(CONFIG_USB4)		+= thunderbolt/
>   obj-$(CONFIG_CORESIGHT)		+= hwtracing/coresight/
>   obj-y				+= hwtracing/intel_th/
> +obj-y				+= hwtracing/qcom/
>   obj-$(CONFIG_STM)		+= hwtracing/stm/
>   obj-$(CONFIG_HISI_PTT)		+= hwtracing/ptt/
>   obj-y				+= android/
> diff --git a/drivers/hwtracing/Kconfig b/drivers/hwtracing/Kconfig
> index 911ee977103c..8a640218eed8 100644
> --- a/drivers/hwtracing/Kconfig
> +++ b/drivers/hwtracing/Kconfig
> @@ -7,4 +7,6 @@ source "drivers/hwtracing/intel_th/Kconfig"
>   
>   source "drivers/hwtracing/ptt/Kconfig"
>   
> +source "drivers/hwtracing/qcom/Kconfig"
> +
>   endmenu
> diff --git a/drivers/hwtracing/qcom/Kconfig b/drivers/hwtracing/qcom/Kconfig
> new file mode 100644
> index 000000000000..5c94c75ffa39
> --- /dev/null
> +++ b/drivers/hwtracing/qcom/Kconfig
> @@ -0,0 +1,20 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +#
> +# QCOM specific hwtracing drivers
> +#
> +menu "Qualcomm specific hwtracing drivers"
> +
> +config QCOM_TGU
> +	tristate "QCOM Trigger Generation Unit driver"
> +	depends on ARCH_QCOM || COMPILE_TEST
> +	depends on ARM_AMBA
> +	help
> +	  This driver provides support for Trigger Generation Unit that is
> +	  used to detect patterns or sequences on a given set of signals.
> +	  TGU is used to monitor a particular bus within a given region to
> +	  detect illegal transaction sequences or slave responses. It is also
> +	  used to monitor a data stream to detect protocol violations and to
> +	  provide a trigger point for centering data around a specific event
> +	  within the trace data buffer.
> +
> +endmenu
> diff --git a/drivers/hwtracing/qcom/Makefile b/drivers/hwtracing/qcom/Makefile
> new file mode 100644
> index 000000000000..5a0a868c1ea0
> --- /dev/null
> +++ b/drivers/hwtracing/qcom/Makefile
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +obj-$(CONFIG_QCOM_TGU) += tgu.o
> diff --git a/drivers/hwtracing/qcom/tgu.c b/drivers/hwtracing/qcom/tgu.c
> new file mode 100644
> index 000000000000..9c7dd4a09f02
> --- /dev/null
> +++ b/drivers/hwtracing/qcom/tgu.c
> @@ -0,0 +1,192 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + */
> +
> +#include <linux/amba/bus.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/pm_runtime.h>
> +
> +#include "tgu.h"
> +
> +static void tgu_write_all_hw_regs(struct tgu_drvdata *drvdata)
> +{
> +	TGU_UNLOCK(drvdata->base);
> +	/* Enable TGU to program the triggers */
> +	writel(1, drvdata->base + TGU_CONTROL);
> +	TGU_LOCK(drvdata->base);
> +}
> +
> +static void tgu_enable(struct tgu_drvdata *drvdata)
> +{
> +	tgu_write_all_hw_regs(drvdata);
> +	drvdata->enabled = true;
> +}
> +
> +static void tgu_disable(struct tgu_drvdata *drvdata)
> +{
> +	TGU_UNLOCK(drvdata->base);
> +	writel(0, drvdata->base + TGU_CONTROL);
> +	TGU_LOCK(drvdata->base);
> +
> +	drvdata->enabled = false;
> +}
> +
> +static ssize_t enable_tgu_show(struct device *dev,
> +			       struct device_attribute *attr, char *buf)
> +{
> +	struct tgu_drvdata *drvdata = dev_get_drvdata(dev);
> +	bool enabled;
> +
> +	scoped_guard(mutex, &drvdata->lock)
> +		enabled = drvdata->enabled;
> +
> +	return sysfs_emit(buf, "%d\n", enabled);
> +}
> +
> +/* enable_tgu_store - Enable or disable the Trigger Generation Unit (TGU). */
> +static ssize_t enable_tgu_store(struct device *dev,
> +				struct device_attribute *attr,
> +				const char *buf,
> +				size_t size)
> +{
> +	struct tgu_drvdata *drvdata = dev_get_drvdata(dev);
> +	unsigned long val;
> +	int ret;
> +
> +	ret = kstrtoul(buf, 0, &val);
> +	if (ret || val > 1)
> +		return -EINVAL;
> +
> +	/*
> +	 * Hold the mutex across the whole check-and-act sequence: the check of
> +	 * drvdata->enabled, the PM runtime reference counting and the state
> +	 * update must be atomic, otherwise concurrent writers could each
> +	 * imbalance the PM runtime usage counter.
> +	 */
> +	guard(mutex)(&drvdata->lock);
> +
> +	if (val) {
> +		if (drvdata->enabled)
> +			return -EBUSY;
> +
> +		ret = pm_runtime_resume_and_get(dev);
> +		if (ret)
> +			return ret;
> +
> +		tgu_enable(drvdata);
> +	} else {
> +		if (!drvdata->enabled)
> +			return -EINVAL;
> +
> +		tgu_disable(drvdata);
> +		pm_runtime_put(dev);
> +	}
> +
> +	return size;
> +}
> +static DEVICE_ATTR_RW(enable_tgu);
> +
> +static struct attribute *tgu_common_attrs[] = {
> +	&dev_attr_enable_tgu.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group tgu_common_grp = {
> +	.attrs = tgu_common_attrs,
> +};
> +
> +static const struct attribute_group *tgu_attr_groups[] = {
> +	&tgu_common_grp,
> +	NULL,
> +};
> +
> +static int tgu_probe(struct amba_device *adev, const struct amba_id *id)
> +{
> +	struct device *dev = &adev->dev;
> +	struct tgu_drvdata *drvdata;
> +	int ret;
> +
> +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> +	if (!drvdata)
> +		return -ENOMEM;
> +
> +	drvdata->dev = &adev->dev;
> +	dev_set_drvdata(dev, drvdata);
> +
> +	drvdata->base = devm_ioremap_resource(dev, &adev->res);
> +	if (IS_ERR(drvdata->base))
> +		return PTR_ERR(drvdata->base);
> +
> +	ret = devm_mutex_init(dev, &drvdata->lock);
> +	if (ret)
> +		return ret;
> +
> +	drvdata->enabled = false;
> +
> +	ret = sysfs_create_groups(&dev->kobj, tgu_attr_groups);
> +	if (ret) {
> +		dev_err(dev, "failed to create sysfs groups: %d\n", ret);
> +		return ret;
> +	}
> +
> +	pm_runtime_put(&adev->dev);
> +
> +	return 0;
> +}
> +
> +static void tgu_remove(struct amba_device *adev)
> +{
> +	struct device *dev = &adev->dev;
> +	struct tgu_drvdata *drvdata = dev_get_drvdata(dev);
> +
> +	sysfs_remove_groups(&dev->kobj, tgu_attr_groups);
> +
> +	/*
> +	 * If the device is still enabled through sysfs, disable the hardware
> +	 * and drop the PM runtime reference taken in enable_tgu_store() so the
> +	 * usage counter stays balanced. Use the synchronous put: the driver core
> +	 * disables runtime PM right after ->remove() returns, and the barrier in
> +	 * pm_runtime_disable() would cancel a still-queued async idle/suspend,
> +	 * leaving the runtime-PM state inconsistent.
> +	 */
> +	scoped_guard(mutex, &drvdata->lock) {
> +		if (drvdata->enabled) {
> +			tgu_disable(drvdata);
> +			pm_runtime_put_sync(dev);
> +		}
> +	}
> +}
> +
> +static const struct amba_id tgu_ids[] = {
> +	{
> +		.id = 0x000f0e00,
> +		.mask = 0x000fffff,
> +	},
> +	{ 0, 0, NULL },
> +};
> +
> +MODULE_DEVICE_TABLE(amba, tgu_ids);
> +
> +static struct amba_driver tgu_driver = {
> +	.drv = {
> +		.name = "qcom-tgu",
> +		.suppress_bind_attrs = true,
> +	},
> +	.probe = tgu_probe,
> +	.remove = tgu_remove,
> +	.id_table = tgu_ids,
> +};
> +
> +module_amba_driver(tgu_driver);
> +
> +MODULE_AUTHOR("Songwei Chai <songwei.chai@oss.qualcomm.com>");
> +MODULE_AUTHOR("Jinlong Mao <jinlong.mao@oss.qualcomm.com>");
> +MODULE_DESCRIPTION("Qualcomm Trigger Generation Unit driver");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/hwtracing/qcom/tgu.h b/drivers/hwtracing/qcom/tgu.h
> new file mode 100644
> index 000000000000..ebba49402a20
> --- /dev/null
> +++ b/drivers/hwtracing/qcom/tgu.h
> @@ -0,0 +1,51 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + */
> +
> +#ifndef _QCOM_TGU_H
> +#define _QCOM_TGU_H
> +
> +/* Register addresses */
> +#define TGU_CONTROL		0x0000
> +#define TGU_LAR		0xfb0
> +#define TGU_UNLOCK_OFFSET	0xc5acce55
> +
> +static inline void TGU_LOCK(void __iomem *addr)
> +{
> +	do {
> +		/* Wait for things to settle */
> +		mb();
> +		writel_relaxed(0x0, addr + TGU_LAR);
> +	} while (0);
> +}

This is simply replicating the CS_LOCK/CS_UNLOCK.
I don't mind those (and relevant definitions) to be moved into 
include/linux/coresight.h and reused for your driver.

The rest looks fine by me.

Suzuki


> +
> +static inline void TGU_UNLOCK(void __iomem *addr)
> +{
> +	do {
> +		writel_relaxed(TGU_UNLOCK_OFFSET, addr + TGU_LAR);
> +		/* Make sure everyone has seen this */
> +		mb();
> +	} while (0);
> +}
> +
> +/**
> + * struct tgu_drvdata - Data structure for a TGU (Trigger Generation Unit)
> + * @base: Memory-mapped base address of the TGU device
> + * @dev: Pointer to the associated device structure
> + * @lock: Mutex serialising enable/disable and the associated PM runtime
> + *        reference counting against concurrent sysfs access
> + * @enabled: Flag indicating whether the TGU device is enabled
> + *
> + * This structure defines the data associated with a TGU device,
> + * including its base address, device pointer, the lock serialising
> + * enable/disable, and the enable status.
> + */
> +struct tgu_drvdata {
> +	void __iomem *base;
> +	struct device *dev;
> +	struct mutex lock;
> +	bool enabled;
> +};
> +
> +#endif