perfetto: Create a common MesaRenderpassIncrementalState.

... and explain what its role is.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22350>

src/freedreno/vulkan/tu_perfetto.cc

@@ -109,12 +109,8 @@ static uint64_t last_suspend_count;
 static uint64_t gpu_max_timestamp;
 static uint64_t gpu_timestamp_offset;
 
-struct TuRenderpassIncrementalState {
-   bool was_cleared = true;
-};
-
 struct TuRenderpassTraits : public perfetto::DefaultDataSourceTraits {
-   using IncrementalStateType = TuRenderpassIncrementalState;
+   using IncrementalStateType = MesaRenderpassIncrementalState;
 };
 
 class TuRenderpassDataSource : public MesaRenderpassDataSource<TuRenderpassDataSource,

src/gallium/drivers/freedreno/freedreno_perfetto.cc

@@ -22,12 +22,8 @@ static uint64_t next_clock_sync_ns; /* cpu time of next clk sync */
  */
 static uint64_t sync_gpu_ts;
 
-struct FdRenderpassIncrementalState {
-   bool was_cleared = true;
-};
-
 struct FdRenderpassTraits : public perfetto::DefaultDataSourceTraits {
-   using IncrementalStateType = FdRenderpassIncrementalState;
+   using IncrementalStateType = MesaRenderpassIncrementalState;
 };
 
 class FdRenderpassDataSource : public MesaRenderpassDataSource<FdRenderpassDataSource, FdRenderpassTraits> {

src/gallium/drivers/radeonsi/si_perfetto.cpp

@@ -50,12 +50,8 @@ static const struct {
    }
 };
 
-struct SIRenderpassIncrementalState {
-   bool was_cleared = true;
-};
-
 struct SIRenderpassTraits : public perfetto::DefaultDataSourceTraits {
-   using IncrementalStateType = SIRenderpassIncrementalState;
+   using IncrementalStateType = MesaRenderpassIncrementalState;
 };
 
 class SIRenderpassDataSource : public MesaRenderpassDataSource<SIRenderpassDataSource, 

src/intel/ds/intel_driver_ds.cc

@@ -105,12 +105,8 @@ static const struct {
    },
 };
 
-struct IntelRenderpassIncrementalState {
-   bool was_cleared = true;
-};
-
 struct IntelRenderpassTraits : public perfetto::DefaultDataSourceTraits {
-   using IncrementalStateType = IntelRenderpassIncrementalState;
+   using IncrementalStateType = MesaRenderpassIncrementalState;
 };
 
 class IntelRenderpassDataSource : public MesaRenderpassDataSource<IntelRenderpassDataSource,

src/panfrost/vulkan/panvk_utrace_perfetto.cc

@@ -20,12 +20,8 @@
 #include "panvk_tracepoints_perfetto.h"
 #include "panvk_utrace.h"
 
-struct PanVKRenderpassIncrementalState {
-   bool was_cleared = true;
-};
-
 struct PanVKRenderpassTraits : public perfetto::DefaultDataSourceTraits {
-   using IncrementalStateType = PanVKRenderpassIncrementalState;
+   using IncrementalStateType = MesaRenderpassIncrementalState;
 };
 
 class PanVKRenderpassDataSource

src/util/perf/u_perfetto_renderpass.h

@@ -27,6 +27,27 @@
 #include "util/perf/u_trace.h"
 #include "util/ralloc.h"
 
+/**
+ * Struct tracking state during a perfetto packet sequence
+ *
+ * Sometimes perfetto loses state, and starts a new packet sequence to
+ * recover. One common example is when you start perfetto tracing after the
+ * driver is up and running -- all perfetto trace packets had been skipped
+ * until tracing started.
+ *
+ * When we're in a new sequence, we need to detect it (in the form of a new
+ * struct created with was_cleared set), and emit all the driver setup packets
+ * before emitting any tracing that might reference the one-time state
+ * packets.
+ *
+ * Note that incremental state structs are stored in TLS in perfetto, so you
+ * will have more than one per data source, but it also means it's owned for
+ * access by a trace context through tctx.GetIncrementalState().
+ */
+struct MesaRenderpassIncrementalState {
+   bool was_cleared = true;
+};
+
 using perfetto::DataSource;
 template <typename DataSourceType, typename DataSourceTraits>
 class MesaRenderpassDataSource