drm/amd/display: add a debugfs interface for the DMUB trace mask

For features that are implemented primarily in DMUB (e.g. PSR), it is
useful to be able to trace them at a DMUB level from the kernel,
especially when debugging issues. So, introduce a debugfs interface that
is able to read and set the DMUB trace mask dynamically at runtime and
document how to use it.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

2 files changed, 70 insertions, 0 deletions

diff --git a/Documentation/gpu/amdgpu/display/dc-debug.rst b/Documentation/gpu/amdgpu/display/dc-debug.rst
index 40c55a618918..817631b1dbf3 100644
--- a/Documentation/gpu/amdgpu/display/dc-debug.rst
+++ b/Documentation/gpu/amdgpu/display/dc-debug.rst
@@ -75,3 +75,44 @@ change in real-time by using something like::
 
 When reporting a bug related to DC, consider attaching this log before and
 after you reproduce the bug.
+
+DMUB Firmware Debug
+===================
+
+Sometimes, dmesg logs aren't enough. This is especially true if a feature is
+implemented primarily in DMUB firmware. In such cases, all we see in dmesg when
+an issue arises is some generic timeout error. So, to get more relevant
+information, we can trace DMUB commands by enabling the relevant bits in
+`amdgpu_dm_dmub_trace_mask`.
+
+Currently, we support the tracing of the following groups:
+
+Trace Groups
+------------
+
+.. csv-table::
+   :header-rows: 1
+   :widths: 1, 1
+   :file: ./trace-groups-table.csv
+
+**Note: Not all ASICs support all of the listed trace groups**
+
+So, to enable just PSR tracing you can use the following command::
+
+  # echo 0x8020 > /sys/kernel/debug/dri/0/amdgpu_dm_dmub_trace_mask
+
+Then, you need to enable logging trace events to the buffer, which you can do
+using the following::
+
+  # echo 1 > /sys/kernel/debug/dri/0/amdgpu_dm_dmcub_trace_event_en
+
+Lastly, after you are able to reproduce the issue you are trying to debug,
+you can disable tracing and read the trace log by using the following::
+
+  # echo 0 > /sys/kernel/debug/dri/0/amdgpu_dm_dmcub_trace_event_en
+  # cat /sys/kernel/debug/dri/0/amdgpu_dm_dmub_tracebuffer
+
+So, when reporting bugs related to features such as PSR and ABM, consider
+enabling the relevant bits in the mask before reproducing the issue and
+attach the log that you obtain from the trace buffer in any bug reports that you
+create.
diff --git a/Documentation/gpu/amdgpu/display/trace-groups-table.csv b/Documentation/gpu/amdgpu/display/trace-groups-table.csv
new file mode 100644
index 000000000000..3f6a50d1d883
--- /dev/null
+++ b/Documentation/gpu/amdgpu/display/trace-groups-table.csv
@@ -0,0 +1,29 @@
+Name, Mask Value
+INFO, 0x1
+IRQ SVC, 0x2
+VBIOS, 0x4
+REGISTER, 0x8
+PHY DBG, 0x10
+PSR, 0x20
+AUX, 0x40
+SMU, 0x80
+MALL, 0x100
+ABM, 0x200
+ALPM, 0x400
+TIMER, 0x800
+HW LOCK MGR, 0x1000
+INBOX1, 0x2000
+PHY SEQ, 0x4000
+PSR STATE, 0x8000
+ZSTATE, 0x10000
+TRANSMITTER CTL, 0x20000
+PANEL CNTL, 0x40000
+FAMS, 0x80000
+DPIA, 0x100000
+SUBVP, 0x200000
+INBOX0, 0x400000
+SDP, 0x4000000
+REPLAY, 0x8000000
+REPLAY RESIDENCY, 0x20000000
+CURSOR INFO, 0x80000000
+IPS, 0x100000000