1 files changed, 156 insertions, 0 deletions
diff --git a/hifi/xaf/hifi-dpf/core/util/mutex.c b/hifi/xaf/hifi-dpf/core/util/mutex.c
new file mode 100644
index 00000000..d62a6a17
--- /dev/null
+++ b/hifi/xaf/hifi-dpf/core/util/mutex.c
@@ -0,0 +1,156 @@
+/*******************************************************************************
+* Copyright (C) 2018 Cadence Design Systems, Inc.
+* 
+* Permission is hereby granted, free of charge, to any person obtaining
+* a copy of this software and associated documentation files (the
+* "Software"), to use this Software with Cadence processor cores only and 
+* not with any other processors and platforms, subject to
+* the following conditions:
+* 
+* The above copyright notice and this permission notice shall be included
+* in all copies or substantial portions of the Software.
+* 
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+******************************************************************************/
+
+/*******************************************************************************
+ * mutex.c
+ *
+ * Implementation of non-robust Szymanski linear-waiting algorithm. Types of
+ * failures tolerated by Szymanski's "robust" algorithm are not specific for
+ * Xtensa DSP cluster and therefore more lightweight version of the algorithm
+ * is used. FIFO servicing property is of low importance, and faster/smaller
+ * version with linear-wait property is preferable.
+ ******************************************************************************/
+ 
+#include "xf.h"
+
+/*******************************************************************************
+ * Local constants definitions
+ ******************************************************************************/
+
+/* ...communication variables */
+#define __M_A                           (1 << 0)
+#define __M_W                           (1 << 1)
+#define __M_S                           (1 << 2)
+
+/* ...process states (updated atomically) */
+#define M_PASSIVE                       (0)
+#define M_ENTRY                         (__M_A)
+#define M_INSIDE                        (__M_W)
+#define M_TRANSIENT                     (__M_S | __M_W)
+#define M_EXIT                          (__M_S)
+
+/* ...total number of cores */
+#define M_N                             XF_CFG_CORES_NUM
+
+/* ...do not compile the code if there is just a single core */
+#if M_N > 1
+/*******************************************************************************
+ * Entry points
+ ******************************************************************************/
+
+void mutex_lock(u32 i)
+{
+    u32     j;
+    
+    /* ...p1: i-th core goes into "entry" state (aws = true,false,false) */
+    MUTEX_SHARED_WRITE(i, M_ENTRY);
+
+    /* ...p2: wait all processes have sj=false (waiting room door is open) */
+    for (j = 0; j < M_N; j++)
+    {
+        /* ...wait until sj = false */
+        while (MUTEX_SHARED_READ(j) & __M_S) (void) 0;
+    }
+    
+    /* ...p3: i-th core enters "inside" state (aws = false,true,false) */
+    MUTEX_SHARED_WRITE(i, M_INSIDE);
+
+p4:
+    /* ...p4: wait in "inside" state */
+    for (j = 0; j < M_N; j++)
+    {
+        /* ...p5: check if any of the cores appears is in "entry" state (aj=true) */
+        if (MUTEX_SHARED_READ(j) & __M_A)
+        {
+            /* ...p5: found core in "entry" state (j < n); wait until it enters waiting room */
+            goto p7;
+        }
+    }
+
+    /* ...p6: j == n; enter into "transient" state (ai=false, wi=true, si=true) */
+    MUTEX_SHARED_WRITE(i, M_TRANSIENT);
+
+    /* ...p6.1: check for any core appearing in "entry" room */
+    for (j = 0; j < M_N; j++)
+    {
+        if (MUTEX_SHARED_READ(j) & __M_A)
+        {
+            /* ...p6.2: found core in "entry" state (j < n) */
+            MUTEX_SHARED_WRITE(i, M_INSIDE);
+
+            /* ...back of to the "inside" state */
+            goto p7;
+        }
+    }
+        
+    /* ...p6.3: no cores in "entry" room (j == n); go to "exit" state (ai=false, wi=false, si=true) */
+    MUTEX_SHARED_WRITE(i, M_EXIT);
+
+    /* ...p6.4: allow all cores to leave "transient" state (i.e. switch to "exit") */
+    for (j = 0; j < M_N; j++)
+    {
+        while (MUTEX_SHARED_READ(j) & __M_W) (void) 0;
+    }
+
+    goto p9;
+    
+p7:
+    /* ...j < n condition is met; find any cores in "inside" state (wj = true, sj = false) */
+    for (j = 0; j < M_N; j++)
+    {
+        /* ...check if the core is in "exit" state */
+        if (MUTEX_SHARED_READ(j) == M_EXIT)
+        {
+            /* ...p8.1: different core is a leader; go to "exit" state (ai=false, wi=false, si=true) */
+            MUTEX_SHARED_WRITE(i, M_EXIT);
+
+            goto p9;
+        }
+    }
+
+    /* ...wait in "inside" state while all transients settle */
+    goto p4;
+
+p9:
+    /* ...p9: i-th core is in "exit" state; enter critical section in accordance with numbering */
+    for (j = 0; j < i; j++)
+    {
+        /* ...wait until core with lower number in "inside"/"transient"/"exit" states leaves */
+        while (MUTEX_SHARED_READ(j) & (__M_W | __M_S)) (void) 0;
+    }
+    
+    /* ...critical section entered */
+}
+
+/*******************************************************************************
+ * mutex_unlock
+ *
+ * Release multi-core mutex
+ ******************************************************************************/
+
+void mutex_unlock(u32 i)
+{
+    /* ...enter into "passive" state (ai=false, wi=false, si=false) */
+    MUTEX_SHARED_WRITE(i, M_PASSIVE);
+}
+
+#endif  /* M_N > 1 */