initial cache-support

utility/imxrt_hw.cpp

 	CCM_ANALOG_PLL_AUDIO = 0;
 	//CCM_ANALOG_PLL_AUDIO |= CCM_ANALOG_PLL_AUDIO_BYPASS;
 	CCM_ANALOG_PLL_AUDIO |= CCM_ANALOG_PLL_AUDIO_ENABLE
-			     | CCM_ANALOG_PLL_AUDIO_POST_DIV_SELECT(2) // 0: 1/4; 1: 1/2; 0: 1/1
+			     | CCM_ANALOG_PLL_AUDIO_POST_DIV_SELECT(2) // 2: 1/4; 1: 1/2; 0: 1/1
 			     | CCM_ANALOG_PLL_AUDIO_DIV_SELECT(nfact);
 
 	CCM_ANALOG_PLL_AUDIO_NUM   = nmult & CCM_ANALOG_PLL_AUDIO_NUM_MASK;

utility/imxrt_hw.h

 #ifndef imxr_hw_h_
 #define imxr_hw_h_
 
+#define IMXRT_CACHE_ENABLED 2 // 0=disabled, 1=WT, 2= WB
+
 #include <Arduino.h>
 #include <imxrt.h>
 
 void set_audioClock(int nfact, int32_t nmult, uint32_t ndiv); // sets PLL4
 
 #endif
+
+#else
+//No IMXRT
+#define IMXRT_CACHE_ENABLED 0
 #endif
+