xref: /OK3568_Linux_fs/kernel/Documentation/csf_sync_state_dump.txt (revision 4882a59341e53eb6f0b4789bf948001014eff981)

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DebugFS interface:
------------------

A new per-kbase-context debugfs file called csf_sync has been implemented
which captures the current KCPU & GPU queue state of the not-yet-completed
operations and displayed through the debugfs file.
This file is at:
=======================================================
/sys/kernel/debug/mali0/ctx/<pid>_<context id>/csf_sync
=======================================================

Output Format:
----------------

The csf_sync file contains important data for the currently active queues.
This data is formatted into two segments, which are separated by a
pipe character: the common properties and the operation-specific properties.

Common Properties:
------------------

* Queue type: GPU or KCPU.
* kbase context id and the queue id.
* If the queue type is a GPU queue then the group handle is also noted,
in the middle of the other two IDs. The slot value is also dumped.
* Execution status, which can either be 'P' for pending or 'S' for started.
* Command type is then output which indicates the type of dependency
(i.e. wait or signal).
* Object address which is a pointer to the sync object that the
command operates on.
* The live value, which is the value of the synchronization object
at the time of dumping. This could help to determine why wait
operations might be blocked.

Operation-Specific Properties:
------------------------------

The operation-specific values for KCPU queue fence operations
are as follows: a unique timeline name, timeline context, and a fence
sequence number. The CQS WAIT and CQS SET are denoted in the sync dump
as their OPERATION counterparts, and therefore show the same operation
specific values; the argument value to wait on or set to, and operation type,
being (by definition) op:gt and op:set for CQS_WAIT and CQS_SET respectively.

There are only two operation-specific values for operations in GPU queues
which are always shown; the argument value to wait on or set/add to,
and the operation type (set/add) or wait condition (e.g. LE, GT, GE).

Examples
--------
GPU Queue Example
------------------

The following output is of a GPU queue, from a process that has a KCTX ID of 52,
is in Queue Group (CSG) 0, and has Queue ID 0. It has started and is waiting on
the object at address 0x0000007f81ffc800. The live value is 0,
as is the arg value. However, the operation "op" is GT, indicating it's waiting
for the live value to surpass the arg value:

======================================================================================================================================
queue:GPU-52-0-0 exec:S cmd:SYNC_WAIT slot:4 obj:0x0000007f81ffc800 live_value:0x0000000000000000 | op:gt arg_value:0x0000000000000000
======================================================================================================================================

The following is an example of GPU queue dump, where the SYNC SET operation
is blocked by the preceding SYNC WAIT operation. This shows two GPU queues,
with the same KCTX ID of 8, Queue Group (CSG) 0, and Queue ID 0. The SYNC WAIT
operation has started, while the SYNC SET is pending, blocked by the SYNC WAIT.
Both operations are on the same slot, 2 and have live value of 0. The SYNC WAIT
is waiting on the object at address 0x0000007f81ffc800, while the SYNC SET will
set the object at address 0x00000000a3bad4fb when it is unblocked.
The operation "op" is GT for the SYNC WAIT, indicating it's waiting for the
live value to surpass the arg value, while the operation and arg value for the
SYNC SET is "set" and "1" respectively:

======================================================================================================================================
queue:GPU-8-0-0 exec:S cmd:SYNC_WAIT slot:2 obj:0x0000007f81ffc800 live_value:0x0000000000000000 | op:gt arg_value:0x0000000000000000
queue:GPU-8-0-0 exec:P cmd:SYNC_SET slot:2 obj:0x00000000a3bad4fb live_value:0x0000000000000000 | op:set arg_value:0x0000000000000001
======================================================================================================================================

KCPU Queue Example
------------------

The following is an example of a KCPU queue, from a process that has
a KCTX ID of 0 and has Queue ID 1. It has started and is waiting on the
object at address 0x0000007fbf6f2ff8. The live value is currently 0 with
the "op" being GT indicating it is waiting on the live value to
surpass the arg value.

===============================================================================================================================
queue:KCPU-0-1 exec:S cmd:CQS_WAIT_OPERATION obj:0x0000007fbf6f2ff8 live_value:0x0000000000000000 | op:gt arg_value: 0x00000000
===============================================================================================================================