SDRAM: turn SDRAM_START_ADDRESS into variable

SDRAM_START_ADDRESS is being used in various places instead of trusting the APIs.
In case the M4 is in standalone mode, no RAM remapping should be used, but if both M7 and M4 want to access the SDRAM, the address they are referring to should be the same.
By initializing SDRAM object very early, we can spot is RAM was already initialized (and chenge the user selection accordingly)

Author: facchinm

libraries/Arduino_H7_Video/src/dsi.cpp

@@ -51,6 +51,8 @@ int dsi_init(uint8_t bus, struct edid *edid, struct display_timing *dt) {
 	static const uint32_t DSI_PLLIDF = DSI_PLL_IN_DIV3;
 	static const uint32_t DSI_PLLODF = DSI_PLL_OUT_DIV1;
 	static const uint32_t DSI_TXEXCAPECLOCKDIV = 4;
+	#undef HSE_VALUE
+	#define HSE_VALUE 16000000
 #else
 	static const uint32_t DSI_PLLNDIV = 40;
 	static const uint32_t DSI_PLLIDF = DSI_PLL_IN_DIV2;

libraries/Portenta_SDRAM/src/SDRAM.cpp

@@ -3,6 +3,19 @@ extern "C" {
 	#include "ram_internal.h"
 }
 
+uint32_t SDRAM_START_ADDRESS = SDRAM_START_ADDRESS_DEFAULT;
+uint32_t SDRAM_END_ADDRESS = SDRAM_END_ADDRESS_DEFAULT;
+
+SDRAMClass::SDRAMClass() {
+#ifdef CORE_CM4
+    if (FMC_SDRAM_DEVICE->SDCMR != 0x00000000U) {
+        // CM4 not standalone, RAM already remapped to 0x60000000
+        SDRAM_START_ADDRESS = 0x60000000;
+        SDRAM_END_ADDRESS = 0x60800000;
+    }
+#endif
+}
+
 int SDRAMClass::begin(uint32_t start_address) {
 
 	//printf("FMC_SDRAM_DEVICE->SDCMR: %x\n", FMC_SDRAM_DEVICE->SDCMR);
@@ -59,7 +72,11 @@ int SDRAMClass::begin(uint32_t start_address) {
 		mpu_config_end();
 #endif
 
-	}
+	} else {
+#ifdef CORE_CM4
+        start_address = SDRAM_START_ADDRESS | (start_address & 0xFFFFFF);
+#endif
+    }
 
 	if (start_address) {
 		//printf("malloc_addblock: allocate %d bytes\n", SDRAM_END_ADDRESS - start_address);
@@ -126,4 +143,4 @@ bool __attribute__((optimize("O0"))) SDRAMClass::test(bool fast) {
     return true;
 }
 
-SDRAMClass SDRAM;
+SDRAMClass SDRAM __attribute__ ((init_priority (101)));

libraries/Portenta_SDRAM/src/SDRAM.h

@@ -5,16 +5,19 @@
 #include "Arduino.h"
 
 #if !defined(CORE_CM4)
-#define SDRAM_END_ADDRESS			(0x60800000)
-#define SDRAM_START_ADDRESS			(0x60000000)
+#define SDRAM_END_ADDRESS_DEFAULT			(0x60800000)
+#define SDRAM_START_ADDRESS_DEFAULT			(0x60000000)
 #else
-#define SDRAM_END_ADDRESS			(0xC0800000)
-#define SDRAM_START_ADDRESS			(0xC0000000)
+#define SDRAM_END_ADDRESS_DEFAULT			(0xC0800000)
+#define SDRAM_START_ADDRESS_DEFAULT			(0xC0000000)
 #endif
 
+extern uint32_t SDRAM_START_ADDRESS;
+extern uint32_t SDRAM_END_ADDRESS;
+
 class SDRAMClass {
 public:
-	SDRAMClass() {}
+	SDRAMClass();
 	int begin(uint32_t start_address = SDRAM_START_ADDRESS);
 	void* malloc(size_t size);
 	void free(void* ptr);