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+What: /sys/bus/coresight/devices/ultra_smb<N>/enable_sink
+Date: October 2022
+KernelVersion: 6.1
+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: October 2022
+KernelVersion: 6.1
+Contact: Junhao He <hejunhao3@huawei.com>
+Description: (Read) Shows the buffer size of each UltraSoc SMB device.
+
+What: /sys/bus/coresight/devices/ultra_smb<N>/mgmt/buf_status
+Date: October 2022
+KernelVersion: 6.1
+Contact: Junhao He <hejunhao3@huawei.com>
+Description: (Read) Shows the value held by UltraSoc SMB status register.
+ BIT(0) is zero means buffer is empty.
+
+What: /sys/bus/coresight/devices/ultra_smb<N>/mgmt/read_pos
+Date: October 2022
+KernelVersion: 6.1
+Contact: Junhao He <hejunhao3@huawei.com>
+Description: (Read) Shows the value held by UltraSoc SMB Read Pointer register.
+
+What: /sys/bus/coresight/devices/ultra_smb<N>/mgmt/write_pos
+Date: October 2022
+KernelVersion: 6.1
+Contact: Junhao He <hejunhao3@huawei.com>
+Description: (Read) Shows the value held by UltraSoc SMB Write Pointer register.
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+.. SPDX-License-Identifier: GPL-2.0
+
+======================================
+UltraSoc - HW Assisted Tracing on SoC
+======================================
+ :Author: Qi Liu <liuqi115@huawei.com>
+ :Date: March 2022
+
+Introduction
+------------
+
+UltraSoc SMB is a per SCCL(Super CPU Cluster) hardware, and it provides a
+way to buffer and store CPU trace messages in a region of shared system
+memory. SMB is plugged as a coresight sink device and the corresponding
+trace generators (ETM) are plugged in as source devices.
+
+Sysfs files and directories
+---------------------------
+
+The SMB devices appear on the existing coresight bus alongside the other
+coresight devices::
+
+ $# ls /sys/bus/coresight/devices/
+ ultra_smb0 ultra_smb1 ultra_smb2 ultra_smb3
+
+The ``ultra_smb<N>`` named SMB 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 held by UltraSoc SMB Read Pointer register.
+ * ``write_pos``: Shows the value held by UltraSoc SMB Write Pointer register.
+ * ``buf_status``: Shows the value held by UltraSoc SMB status register.
+ BIT(0) is zero means buffer is empty.
+ * ``buf_size``: Shows the buffer size of each UltraSoc SMB device.
+
+Firmware Bindings
+---------------------------
+
+SMB device is only supported with ACPI, and ACPI binding of SMB device
+describes SMB device indentifier, resource information and graph structure.
+
+SMB is identified by ACPI HID "HISI03A1", resource of device is declared using
+the _CRS method. Each SMB must present two base address, the first one is the
+configuration base address of SMB device, the second one is the base address of
+shared system memory.
+
+examples::
+
+ Device(USMB) { \
+ Name(_HID, "HISI03A1") \
+ Name(_CRS, ResourceTemplate() { \
+ MEM_RESRC(0x95100000, 0x951FFFFF, 0x100000) \
+ MEM_RESRC(0x50000000, 0x53FFFFFF, 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}, \
+ } \
+ } \
+ }) \
+ }