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},       \
      }                                                      \
    }                                                        \
  })                                                         \
}