powerpc: Cleanup udbg_16550 and add support for LPC PIO-only UARTs

The udbg_16550 code, which we use for our early consoles and debug
backends was fairly messy. Especially for the debug consoles, it
would re-implement the "high level" getc/putc/poll functions for
each access method. It also had code to configure the UART but only
for the straight MMIO method.

This changes it to instead abstract at the register accessor level,
and have the various functions and configuration routines use these.

The result is simpler and slightly smaller code, and free support
for non-MMIO mapped PIO UARTs, which such as the ones that can be
present on a POWER 8 LPC bus.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/udbg.h

@@ -27,10 +27,11 @@ extern void udbg_printf(const char *fmt, ...)
 	__attribute__ ((format (printf, 1, 2)));
 extern void udbg_progress(char *s, unsigned short hex);
 
-extern void udbg_init_uart(void __iomem *comport, unsigned int speed,
-			   unsigned int clock);
-extern unsigned int udbg_probe_uart_speed(void __iomem *comport,
-					  unsigned int clock);
+extern void udbg_uart_init_mmio(void __iomem *addr, unsigned int stride);
+extern void udbg_uart_init_pio(unsigned long port, unsigned int stride);
+
+extern void udbg_uart_setup(unsigned int speed, unsigned int clock);
+extern unsigned int udbg_probe_uart_speed(unsigned int clock);
 
 struct device_node;
 extern void udbg_scc_init(int force_scc);

arch/powerpc/kernel/legacy_serial.c

@@ -221,14 +221,19 @@ static int __init add_legacy_isa_port(struct device_node *np,
 	/* Translate ISA address. If it fails, we still register the port
 	 * with no translated address so that it can be picked up as an IO
 	 * port later by the serial driver
+	 *
+	 * Note: Don't even try on P8 lpc, we know it's not directly mapped
 	 */
-	taddr = of_translate_address(np, reg);
-	if (taddr == OF_BAD_ADDR)
+	if (!of_device_is_compatible(isa_brg, "ibm,power8-lpc")) {
+		taddr = of_translate_address(np, reg);
+		if (taddr == OF_BAD_ADDR)
+			taddr = 0;
+	} else
 		taddr = 0;
 
 	/* Add port, irq will be dealt with later */
-	return add_legacy_port(np, index, UPIO_PORT, be32_to_cpu(reg[1]), taddr,
-			       NO_IRQ, UPF_BOOT_AUTOCONF, 0);
+	return add_legacy_port(np, index, UPIO_PORT, be32_to_cpu(reg[1]),
+			       taddr, NO_IRQ, UPF_BOOT_AUTOCONF, 0);
 
 }
 
@@ -307,19 +312,31 @@ static int __init add_legacy_pci_port(struct device_node *np,
 
 static void __init setup_legacy_serial_console(int console)
 {
-	struct legacy_serial_info *info =
-		&legacy_serial_infos[console];
+	struct legacy_serial_info *info = &legacy_serial_infos[console];
+	struct plat_serial8250_port *port = &legacy_serial_ports[console];
 	void __iomem *addr;
 
-	if (info->taddr == 0)
-		return;
-	addr = ioremap(info->taddr, 0x1000);
-	if (addr == NULL)
-		return;
+	/* Check if a translated MMIO address has been found */
+	if (info->taddr) {
+		addr = ioremap(info->taddr, 0x1000);
+		if (addr == NULL)
+			return;
+		udbg_uart_init_mmio(addr, 1);
+	} else {
+		/* Check if it's PIO and we support untranslated PIO */
+		if (port->iotype == UPIO_PORT && isa_io_special)
+			udbg_uart_init_pio(port->iobase, 1);
+		else
+			return;
+	}
+
+	/* Try to query the current speed */
 	if (info->speed == 0)
-		info->speed = udbg_probe_uart_speed(addr, info->clock);
+		info->speed = udbg_probe_uart_speed(info->clock);
+
+	/* Set it up */
 	DBG("default console speed = %d\n", info->speed);
-	udbg_init_uart(addr, info->speed, info->clock);
+	udbg_uart_setup(info->speed, info->clock);
 }
 
 /*
@@ -367,7 +384,8 @@ void __init find_legacy_serial_ports(void)
 	/* Next, fill our array with ISA ports */
 	for_each_node_by_type(np, "serial") {
 		struct device_node *isa = of_get_parent(np);
-		if (isa && !strcmp(isa->name, "isa")) {
+		if (isa && (!strcmp(isa->name, "isa") ||
+			    !strcmp(isa->name, "lpc"))) {
 			index = add_legacy_isa_port(np, isa);
 			if (index >= 0 && np == stdout)
 				legacy_serial_console = index;