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authorQi Liu <liuqi115@huawei.com>2023-01-14 13:13:02 +0300
committerSuzuki K Poulose <suzuki.poulose@arm.com>2023-01-16 13:16:15 +0300
commit2d4103ae31aa6d5570fd1178ddc68867ab4ab5bd (patch)
treedc0164a8f150635a551ed712ddcb71d1d7bc3282 /Documentation/trace
parent06f5c2926aaa0fba7f99678da6ef77cbbbda1441 (diff)
downloadlinux-2d4103ae31aa6d5570fd1178ddc68867ab4ab5bd.tar.xz
Documentation: Add document for UltraSoc SMB driver
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
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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}, \
+ } \
+ } \
+ }) \
+ }