add support of mini UART in QEMU

build/Makefile

@@ -46,7 +46,13 @@ else
 	QEMU_MACHINE = raspi3
 endif
 
-QEMU_FLAGS = -m 256 -M $(QEMU_MACHINE) -serial stdio
+QEMU_FLAGS = -m 256 -M $(QEMU_MACHINE)
+
+ifeq ($(USE_MINI_UART),1)
+	QEMU_FLAGS += -serial null -serial stdio
+else 
+	QEMU_FLAGS += -serial stdio
+endif
 
 ##################
 # FILES AND DIRS #

include/kernel/io.h

@@ -10,7 +10,7 @@ enum
 #elif BCM2711
     PERIPHERAL_BASE = 0xFE000000,
 #else // BCM2835
-    PERIPHERAL_BASE = 0x7E000000,
+    PERIPHERAL_BASE = 0x7E000000, // try with 0x20000000
 #endif
 
     // The mailbox base address.

src/kernel/mini_uart.c

@@ -9,25 +9,6 @@
 void uart_init()
 {
 	uint32_t selector;
-	
-	// Setup the GPIO pin 14 && 15.
-	selector = mmio_read(GPFSEL1);
-	selector &= ~(7<<12);  // clean gpio14
-	selector |= 2<<12;     // set alt5 for gpio14
-	selector &= ~(7<<15);  // clean gpio15
-	selector |= 2<<15;     // set alt5 for gpio15
-	mmio_write(GPFSEL1, selector);
-
-	// Disable pull up/down for all GPIO pins & delay for 150 cycles.
-	mmio_write(GPPUD, 0x00000000);
-	delay(150);
-
-	// Disable pull up/down for pin 14,15 & delay for 150 cycles.
-	mmio_write(GPPUDCLK0, (1 << 14) | (1 << 15));
-	delay(150);
-
-	// Write 0 to GPPUDCLK0 to make it take effect.
-	mmio_write(GPPUDCLK0, 0x00000000);
 
 	//Enable mini uart (this also enables access to it registers)
 	mmio_write(AUX_ENABLES, 1);
@@ -44,8 +25,28 @@ void uart_init()
 	//Set RTS line to be always high
 	mmio_write(AUX_MU_MCR_REG, 0);
 
+	// Disable interrupts
+	mmio_write(AUX_MU_IIR_REG, 0xc6);
+
 	//Set baud rate to 115200
 	mmio_write(AUX_MU_BAUD_REG, 270);
+	
+	// Setup the GPIO pin 14 && 15.
+	selector = mmio_read(GPFSEL1);
+	selector &=~((7<<12)|(7<<15)); // gpio14, gpio15
+	selector |=(2<<12)|(2<<15);    // alt5
+	mmio_write(GPFSEL1, selector);
+
+	// Disable pull up/down for all GPIO pins & delay for 150 cycles.
+	mmio_write(GPPUD, 0x00000000);
+	delay(150);
+
+	// Disable pull up/down for pin 14,15 & delay for 150 cycles.
+	mmio_write(GPPUDCLK0, (1 << 14) | (1 << 15));
+	delay(150);
+
+	// Write 0 to GPPUDCLK0 to make it take effect.
+	mmio_write(GPPUDCLK0, 0x00000000);
 
 	//Finally, enable transmitter and receiver
 	mmio_write(AUX_MU_CNTL_REG, 3);