Introduce 'GetTickCountLabel' for detecting RTCC reconfigurations

armsrc/appmain.c

@@ -97,7 +97,6 @@ common_area_t g_common_area __attribute__((section(".commonarea")));
 static int button_status = BUTTON_NO_CLICK;
 static bool allow_send_wtx = false;
 static uint32_t g_hf_field_activity_timeout_ms = 0;
-static uint32_t g_last_activity_ms = 0;
 uint16_t g_tearoff_delay_us = 0;
 bool g_tearoff_enabled = false;
 uint8_t g_tearoff_skip = 0;
@@ -1014,7 +1013,6 @@ static void PacketReceived(PacketCommandNG *packet) {
             uint32_t timeout_ms = 0;
             memcpy(&timeout_ms, packet->data.asBytes, sizeof(timeout_ms));
             g_hf_field_activity_timeout_ms = timeout_ms;
-            g_last_activity_ms = GetTickCount();
             reply_ng(CMD_SET_HF_FIELD_TIMEOUT, PM3_SUCCESS, NULL, 0);
             break;
         }
@@ -3333,7 +3331,8 @@ void  __attribute__((noreturn)) AppMain(void) {
     FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
 
     StartTickCount();
-    g_last_activity_ms = GetTickCount();
+    uint32_t last_activity_tick = GetTickCount();
+    uint32_t last_activity_label = GetTickCountLabel();
 
 #ifdef WITH_LCD
     LCDInit();
@@ -3397,14 +3396,19 @@ void  __attribute__((noreturn)) AppMain(void) {
         int ret = receive_ng(&rx);
         if (ret == PM3_SUCCESS) {
             PacketReceived(&rx);
-            g_last_activity_ms = GetTickCount();
+            last_activity_label = GetTickCountLabel();
+            last_activity_tick = GetTickCount();
         } else if (ret != PM3_ENODATA) {
             Dbprintf("Error in frame reception: %d %s", ret, (ret == PM3_EIO) ? "PM3_EIO" : "");
             // TODO if error, shall we resync ?
         }
 
         if (g_hf_field_activity_timeout_ms > 0 && g_hf_field_timeout_active) {
-            if (GetTickCountDelta(g_last_activity_ms) >= g_hf_field_activity_timeout_ms) {
+            uint32_t tickcount_label = GetTickCountLabel();
+            if (tickcount_label != last_activity_label) {
+                last_activity_label = tickcount_label;
+                last_activity_tick = GetTickCount();
+            } else if (GetTickCountDelta(last_activity_tick) >= g_hf_field_activity_timeout_ms) {
                 if (g_dbglevel >= DBG_INFO) {
                     Dbprintf("HF field auto-off: inactivity timeout (%u ms)", g_hf_field_activity_timeout_ms);
                 }

common_arm/ticks.c

@@ -97,7 +97,13 @@ void SpinDelay(int ms) {
 //    SpinDelay(1000);
 //    ti = GetTickCount() - ti;
 //    Dbprintf("timer(1s): %d t=%d", ti, GetTickCount());
+// Increments whenever StartTickCount() reconfigures/resets RTTC.
+// Callers can use this to detect that previously saved tick deltas are no longer valid.
+static uint32_t g_tickcount_label = 0;
+
 void StartTickCount(void) {
+    g_tickcount_label++;
+
     // This timer is based on the slow clock. The slow clock frequency is between 22kHz and 40kHz.
     // We can determine the actual slow clock frequency by looking at the Main Clock Frequency Register.
     while ((AT91C_BASE_PMC->PMC_MCFR & AT91C_CKGR_MAINRDY) == 0);       // Wait for MAINF value to become available...
@@ -122,6 +128,14 @@ uint32_t RAMFUNC GetTickCountDelta(uint32_t start_ticks) {
     return (UINT32_MAX - start_ticks) + stop_ticks;
 }
 
+/*
+* Get current RTTC counter label.
+* If counter config changes between calls, the value is incremented.
+*/
+uint32_t GetTickCountLabel(void) {
+    return g_tickcount_label;
+}
+
 //  -------------------------------------------------------------------------
 //  Timer for iso14443 commands. Uses ssp_clk from FPGA
 //  -------------------------------------------------------------------------

common_arm/ticks.h

@@ -47,6 +47,7 @@ void SpinDelayUsPrecision(int us);  // precision 0.6us , running for 43ms before
 void StartTickCount(void);
 uint32_t RAMFUNC GetTickCount(void);
 uint32_t RAMFUNC GetTickCountDelta(uint32_t start_ticks);
+uint32_t GetTickCountLabel(void);
 
 void ResetUSClock(void);
 void SpinDelayCountUs(uint32_t us);