Documentation: Add document for UltraSoc SMB driver (2d4103ae) · Commits · EulixOS / Software / Kernel

Documentation/ABI/testing/sysfs-bus-coresight-devices-ultra_smb

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		What: /sys/bus/coresight/devices/ultra_smb<N>/enable_sink
		Date: January 2023
		KernelVersion: 6.3
		Contact: Junhao He <hejunhao3@huawei.com>
		Description: (RW) Add/remove a SMB device from a trace path. There can be
		multiple sources for a single SMB device.

		What: /sys/bus/coresight/devices/ultra_smb<N>/mgmt/buf_size
		Date: January 2023
		KernelVersion: 6.3
		Contact: Junhao He <hejunhao3@huawei.com>
		Description: (RO) Shows the buffer size of each UltraSoc SMB device.

		What: /sys/bus/coresight/devices/ultra_smb<N>/mgmt/buf_status
		Date: January 2023
		KernelVersion: 6.3
		Contact: Junhao He <hejunhao3@huawei.com>
		Description: (RO) Shows the value of UltraSoc SMB status register.
		BIT(0) is zero means buffer is empty.

		What: /sys/bus/coresight/devices/ultra_smb<N>/mgmt/read_pos
		Date: January 2023
		KernelVersion: 6.3
		Contact: Junhao He <hejunhao3@huawei.com>
		Description: (RO) Shows the value of UltraSoc SMB Read Pointer register.

		What: /sys/bus/coresight/devices/ultra_smb<N>/mgmt/write_pos
		Date: January 2023
		KernelVersion: 6.3
		Contact: Junhao He <hejunhao3@huawei.com>
		Description: (RO) Shows the value of UltraSoc SMB Write Pointer register.

Documentation/trace/coresight/ultrasoc-smb.rst

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		.. SPDX-License-Identifier: GPL-2.0

		======================================
		UltraSoc - HW Assisted Tracing on SoC
		======================================
		:Author: Qi Liu <liuqi115@huawei.com>
		:Date: January 2023

		Introduction
		------------

		UltraSoc SMB is a per SCCL (Super CPU Cluster) hardware. It provides a
		way to buffer and store CPU trace messages in a region of shared system
		memory. The device acts as a coresight sink device and the
		corresponding trace generators (ETM) are attached as source devices.

		Sysfs files and directories
		---------------------------

		The SMB devices appear on the existing coresight bus alongside other
		devices::

		$# ls /sys/bus/coresight/devices/
		ultra_smb0 ultra_smb1 ultra_smb2 ultra_smb3

		The ``ultra_smb<N>`` names SMB device associated with SCCL.::

		$# ls /sys/bus/coresight/devices/ultra_smb0
		enable_sink mgmt
		$# ls /sys/bus/coresight/devices/ultra_smb0/mgmt
		buf_size buf_status read_pos write_pos

		Key file items are:

		* ``read_pos``: Shows the value on the read pointer register.
		* ``write_pos``: Shows the value on the write pointer register.
		* ``buf_status``: Shows the value on the status register.
		BIT(0) is zero value which means the buffer is empty.
		* ``buf_size``: Shows the buffer size of each device.

		Firmware Bindings
		-----------------

		The device is only supported with ACPI. Its binding describes device
		identifier, resource information and graph structure.

		The device is identified as ACPI HID "HISI03A1". Device resources are allocated
		using the _CRS method. Each device must present two base address; the first one
		is the configuration base address of the device, the second one is the 32-bit
		base address of shared system memory.

		Example::

		Device(USMB) { \
		Name(_HID, "HISI03A1") \
		Name(_CRS, ResourceTemplate() { \
		QWordMemory (ResourceConsumer, , MinFixed, MaxFixed, NonCacheable, \
		ReadWrite, 0x0, 0x95100000, 0x951FFFFF, 0x0, 0x100000) \
		QWordMemory (ResourceConsumer, , MinFixed, MaxFixed, Cacheable, \
		ReadWrite, 0x0, 0x50000000, 0x53FFFFFF, 0x0, 0x4000000) \
		}) \
		Name(_DSD, Package() { \
		ToUUID("ab02a46b-74c7-45a2-bd68-f7d344ef2153"), \
		/* Use CoreSight Graph ACPI bindings to describe connections topology */
		Package() { \
		0, \
		1, \
		Package() { \
		1, \
		ToUUID("3ecbc8b6-1d0e-4fb3-8107-e627f805c6cd"), \
		8, \
		Package() {0x8, 0, \_SB.S00.SL11.CL28.F008, 0}, \
		Package() {0x9, 0, \_SB.S00.SL11.CL29.F009, 0}, \
		Package() {0xa, 0, \_SB.S00.SL11.CL2A.F010, 0}, \
		Package() {0xb, 0, \_SB.S00.SL11.CL2B.F011, 0}, \
		Package() {0xc, 0, \_SB.S00.SL11.CL2C.F012, 0}, \
		Package() {0xd, 0, \_SB.S00.SL11.CL2D.F013, 0}, \
		Package() {0xe, 0, \_SB.S00.SL11.CL2E.F014, 0}, \
		Package() {0xf, 0, \_SB.S00.SL11.CL2F.F015, 0}, \
		} \
		} \
		}) \
		}