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Documentation: Add document for UltraSoc SMB driver

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Bring in documentation for UltraSoc SMB driver.
It simply describes the device, sysfs interface and the
firmware bindings.

Signed-off-by: Qi Liu <liuqi115@huawei.com>
Signed-off-by: Junhao He <hejunhao3@huawei.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230114101302.62320-3-hejunhao3@huawei.com
This commit is contained in:
Qi Liu 2023-01-14 18:13:02 +08:00 committed by Suzuki K Poulose
parent 06f5c2926a
commit 2d4103ae31
2 changed files with 114 additions and 0 deletions
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Documentation/ABI/testing/sysfs-bus-coresight-devices-ultra_smb Normal file
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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.

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Documentation/trace/coresight/ultrasoc-smb.rst Normal file
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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}, \
} \
} \
}) \
}