fdt/serial: Make uart search more agressive. Examine /chosen for serial devices

Change-Id: Icc1673b331d9afb3a7b34c91e7b1f20c3dee964a
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1871
Reviewed-by: Adrien Destugues <[email protected]>
Reviewed-by: Alex von Gluck IV <[email protected]>

src/add-ons/kernel/bus_managers/fdt/fdt_serial.cpp

@@ -40,43 +40,18 @@ extern "C" {
 
 // If we dprintf before the UART is initalized there will be no output
 
-
+static DebugUART*
-DebugUART*
+debug_uart_from_node(const void *fdt, int node)
-debug_uart_from_fdt(const void *fdt)
 {
-	const char *name;
-	int node;
 	int len;
+	const void *prop;
 	phys_addr_t regs;
 	int32 clock = 0;
 	int32 speed = 0;
-	const void *prop;
 	DebugUART *uart = NULL;
 
-	if (fdt == NULL) {
+	if (node < 0 || fdt == NULL)
-		TRACE("%s: No FDT found!\n", __func__);
 		return NULL;
-	}
-
-	name = fdt_get_alias(fdt, "serial");
-	if (name == NULL)
-		name = fdt_get_alias(fdt, "serial0");
-	if (name == NULL)
-		name = fdt_get_alias(fdt, "serial1");
-	if (name == NULL)
-		name = fdt_get_alias(fdt, "uart0");
-	// TODO: else use /chosen linux,stdout-path
-	if (name == NULL) {
-		TRACE("%s: No known FDT UART alias found!\n", __func__);
-		return NULL;
-	}
-
-	node = fdt_path_offset(fdt, name);
-
-	if (node < 0) {
-		TRACE("%s: FDT node not found!\n", __func__);
-		return NULL;
-	}
 
 	// determine the MMIO address
 	regs = fdt_get_device_reg(fdt, node, false);
@@ -86,7 +61,7 @@ debug_uart_from_fdt(const void *fdt)
 		return NULL;
 	}
 
-	TRACE("serial: using '%s', node %d @ %" B_PRIxPHYSADDR "\n",
+	TRACE("serial: checking '%s', node %d @ %" B_PRIxPHYSADDR "\n",
 		name, node, regs);
 
 	// get the UART clock rate
@@ -104,9 +79,9 @@ debug_uart_from_fdt(const void *fdt)
 	}
 
 	// fdt_node_check_compatible returns 0 on match.
-
 	if (fdt_node_check_compatible(fdt, node, "ns16550a") == 0
-		|| fdt_node_check_compatible(fdt, node, "ns16550") == 0) {
+		|| fdt_node_check_compatible(fdt, node, "ns16550") == 0
+		|| fdt_node_check_compatible(fdt, node, "snps,dw-apb-uart") == 0) {
 		TRACE("serial: Found 8250 serial UART!\n");
 		uart = arch_get_uart_8250(regs, clock);
 	#if defined(__arm__)
@@ -124,10 +99,96 @@ debug_uart_from_fdt(const void *fdt)
 		TRACE("serial: Found pl011 serial UART!\n");
 		uart = arch_get_uart_pl011(regs, clock);
 	#endif
-	} else {
+	}
-		// TODO: handle more UART types
+	return uart;
+}
+
+
+DebugUART*
+debug_uart_from_fdt(const void *fdt)
+{
+	int chosen_node;
+	int node;
+	int len;
+	const char *name;
+	const void *prop;
+	DebugUART *uart = NULL;
+
+	if (fdt == NULL) {
+		TRACE("%s: No FDT found!\n", __func__);
 		return NULL;
 	}
 
+	chosen_node = fdt_path_offset(fdt, "/chosen");
+	if (chosen_node >= 0) {
+		prop = fdt_getprop(fdt, chosen_node, "stdout-path", &len);
+		if (prop && len > 0) {
+			node = fdt_path_offset(fdt, (const char*)prop);
+			uart = debug_uart_from_node(fdt, node);
+		}
+		if (uart == NULL) {
+			prop = fdt_getprop(fdt, chosen_node, "linux,stdout-path", &len);
+			if (prop && len > 0) {
+				node = fdt_path_offset(fdt, (const char*)prop);
+				uart = debug_uart_from_node(fdt, node);
+			}
+		}
+
+		if (uart == NULL) {
+			// From what i've seen, stdout is generally an alias.
+			// we could check for "/..." in the prop, but not sure
+			// it's needed. If we *did* check for a prop starting
+			// with / we could make all three of these "the same"
+			prop = fdt_getprop(fdt, chosen_node, "stdout", &len);
+			if (prop && len > 0) {
+				name = fdt_get_alias(fdt, (const char*)prop);
+				if (name != NULL) {
+					node = fdt_path_offset(fdt, name);
+					uart = debug_uart_from_node(fdt, node);
+				}
+			}
+		}
+
+		// Whoo-hoo! Bail.
+		if (uart != NULL)
+			return uart;
+	}
+
+	// If we didn't find a /chosen serial device, lets search for some common aliases
+	char aliases[][8] = {
+		"serial",
+		"serial0",
+		"uart",
+		"uart0",
+		"serial1",
+		"serial2",
+		"serial3",
+		"uart1",
+		"uart2",
+		"uart3"
+	};
+
+	// For each known common serial alias, check it out and see if we have the
+	// needed driver for it. uart0 seems most common.
+	for (int index = 0; index < sizeof(aliases[0]) / sizeof(aliases); index++) {
+		name = fdt_get_alias(fdt, aliases[index]);
+		if (name == NULL)
+			continue;
+
+		node = fdt_path_offset(fdt, name);
+		if (node < 0) {
+			TRACE("%s: FDT node not found!\n", __func__);
+			continue;
+		}
+		uart = debug_uart_from_node(fdt, node);
+
+		// We found a valid serial device. bail.
+		if (uart != NULL)
+			break;
+	}
+
+	// It would be nice if we had *some* communication mechanism here if uart is still
+	// NULL to warn the user that we couldn't find a serial port.
+
 	return uart;
 }