[PATCH v14 2/2] Documentation: Add document for UltraSoc SMB driver

From: Junhao He
Date: Wed Nov 23 2022 - 07:38:14 EST

From: Qi Liu <liuqi115@xxxxxxxxxx>

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

Signed-off-by: Qi Liu <liuqi115@xxxxxxxxxx>
Signed-off-by: Junhao He <hejunhao3@xxxxxxxxxx>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
---
.../sysfs-bus-coresight-devices-ultra_smb | 31 +++++++
.../trace/coresight/ultrasoc-smb.rst | 83 +++++++++++++++++++
2 files changed, 114 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-bus-coresight-devices-ultra_smb
create mode 100644 Documentation/trace/coresight/ultrasoc-smb.rst

diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-ultra_smb b/Documentation/ABI/testing/sysfs-bus-coresight-devices-ultra_smb
new file mode 100644
index 000000000000..deaefd508105
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-ultra_smb
@@ -0,0 +1,31 @@
+What: /sys/bus/coresight/devices/ultra_smb<N>/enable_sink
+Date: November 2022
+KernelVersion: 6.2
+Contact: Junhao He <hejunhao3@xxxxxxxxxx>
+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: November 2022
+KernelVersion: 6.2
+Contact: Junhao He <hejunhao3@xxxxxxxxxx>
+Description: (Read) Shows the buffer size of each UltraSoc SMB device.
+
+What: /sys/bus/coresight/devices/ultra_smb<N>/mgmt/buf_status
+Date: November 2022
+KernelVersion: 6.2
+Contact: Junhao He <hejunhao3@xxxxxxxxxx>
+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: November 2022
+KernelVersion: 6.2
+Contact: Junhao He <hejunhao3@xxxxxxxxxx>
+Description: (Read) Shows the value held by UltraSoc SMB Read Pointer register.
+
+What: /sys/bus/coresight/devices/ultra_smb<N>/mgmt/write_pos
+Date: November 2022
+KernelVersion: 6.2
+Contact: Junhao He <hejunhao3@xxxxxxxxxx>
+Description: (Read) Shows the value held by UltraSoc SMB Write Pointer register.
diff --git a/Documentation/trace/coresight/ultrasoc-smb.rst b/Documentation/trace/coresight/ultrasoc-smb.rst
new file mode 100644
index 000000000000..3f3ebe158272
--- /dev/null
+++ b/Documentation/trace/coresight/ultrasoc-smb.rst
@@ -0,0 +1,83 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================================
+UltraSoc - HW Assisted Tracing on SoC
+======================================
+ :Author: Qi Liu <liuqi115@xxxxxxxxxx>
+ :Date: November 2022
+
+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}, \
+ } \
+ } \
+ }) \
+ }
--
2.33.0