Documentation/trace/coresight/ultrasoc-smb.rst

   1 .. SPDX-License-Identifier: GPL-2.0
   2
   3 ======================================
   4 UltraSoc - HW Assisted Tracing on SoC
   5 ======================================
   6    :Author:   Qi Liu <liuqi115@huawei.com>
   7    :Date:     January 2023
   8
   9 Introduction
  10 ------------
  11
  12 UltraSoc SMB is a per SCCL (Super CPU Cluster) hardware. It provides a
  13 way to buffer and store CPU trace messages in a region of shared system
  14 memory. The device acts as a coresight sink device and the
  15 corresponding trace generators (ETM) are attached as source devices.
  16
  17 Sysfs files and directories
  18 ---------------------------
  19
  20 The SMB devices appear on the existing coresight bus alongside other
  21 devices::
  22
  23         $# ls /sys/bus/coresight/devices/
  24         ultra_smb0   ultra_smb1   ultra_smb2   ultra_smb3
  25
  26 The ``ultra_smb<N>`` names SMB device associated with SCCL.::
  27
  28         $# ls /sys/bus/coresight/devices/ultra_smb0
  29         enable_sink   mgmt
  30         $# ls /sys/bus/coresight/devices/ultra_smb0/mgmt
  31         buf_size  buf_status  read_pos  write_pos
  32
  33 Key file items are:
  34
  35    * ``read_pos``: Shows the value on the read pointer register.
  36    * ``write_pos``: Shows the value on the write pointer register.
  37    * ``buf_status``: Shows the value on the status register.
  38      BIT(0) is zero value which means the buffer is empty.
  39    * ``buf_size``: Shows the buffer size of each device.
  40
  41 Firmware Bindings
  42 -----------------
  43
  44 The device is only supported with ACPI. Its binding describes device
  45 identifier, resource information and graph structure.
  46
  47 The device is identified as ACPI HID "HISI03A1". Device resources are allocated
  48 using the _CRS method. Each device must present two base address; the first one
  49 is the configuration base address of the device, the second one is the 32-bit
  50 base address of shared system memory.
  51
  52 Example::
  53
  54     Device(USMB) {                                               \
  55       Name(_HID, "HISI03A1")                                     \
  56       Name(_CRS, ResourceTemplate() {                            \
  57           QWordMemory (ResourceConsumer, , MinFixed, MaxFixed, NonCacheable, \
  58                        ReadWrite, 0x0, 0x95100000, 0x951FFFFF, 0x0, 0x100000) \
  59           QWordMemory (ResourceConsumer, , MinFixed, MaxFixed, Cacheable, \
  60                        ReadWrite, 0x0, 0x50000000, 0x53FFFFFF, 0x0, 0x4000000) \
  61       })                                                         \
  62       Name(_DSD, Package() {                                     \
  63         ToUUID("ab02a46b-74c7-45a2-bd68-f7d344ef2153"),          \
  64         /* Use CoreSight Graph ACPI bindings to describe connections topology */
  65         Package() {                                              \
  66           0,                                                     \
  67           1,                                                     \
  68           Package() {                                            \
  69             1,                                                   \
  70             ToUUID("3ecbc8b6-1d0e-4fb3-8107-e627f805c6cd"),      \
  71             8,                                                   \
  72             Package() {0x8, 0, \_SB.S00.SL11.CL28.F008, 0},       \
  73             Package() {0x9, 0, \_SB.S00.SL11.CL29.F009, 0},       \
  74             Package() {0xa, 0, \_SB.S00.SL11.CL2A.F010, 0},       \
  75             Package() {0xb, 0, \_SB.S00.SL11.CL2B.F011, 0},       \
  76             Package() {0xc, 0, \_SB.S00.SL11.CL2C.F012, 0},       \
  77             Package() {0xd, 0, \_SB.S00.SL11.CL2D.F013, 0},       \
  78             Package() {0xe, 0, \_SB.S00.SL11.CL2E.F014, 0},       \
  79             Package() {0xf, 0, \_SB.S00.SL11.CL2F.F015, 0},       \
  80           }                                                      \
  81         }                                                        \
  82       })                                                         \
  83     }