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
 	 */
+	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;
+	/* 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;

arch/powerpc/kernel/udbg_16550.c

@@ -18,23 +18,19 @@ extern void real_writeb(u8 data, volatile u8 __iomem *addr);
 extern u8 real_205_readb(volatile u8 __iomem  *addr);
 extern void real_205_writeb(u8 data, volatile u8 __iomem *addr);
 
-struct NS16550 {
-	/* this struct must be packed */
-	unsigned char rbr;  /* 0 */
-	unsigned char ier;  /* 1 */
-	unsigned char fcr;  /* 2 */
-	unsigned char lcr;  /* 3 */
-	unsigned char mcr;  /* 4 */
-	unsigned char lsr;  /* 5 */
-	unsigned char msr;  /* 6 */
-	unsigned char scr;  /* 7 */
-};
-
-#define thr rbr
-#define iir fcr
-#define dll rbr
-#define dlm ier
-#define dlab lcr
+#define UART_RBR	0
+#define UART_IER	1
+#define UART_FCR	2
+#define UART_LCR	3
+#define UART_MCR	4
+#define UART_LSR	5
+#define UART_MSR	6
+#define UART_SCR	7
+#define UART_THR	UART_RBR
+#define UART_IIR	UART_FCR
+#define UART_DLL	UART_RBR
+#define UART_DLM	UART_IER
+#define UART_DLAB	UART_LCR
 
 #define LSR_DR   0x01  /* Data ready */
 #define LSR_OE   0x02  /* Overrun */
@@ -47,52 +43,62 @@ struct NS16550 {
 
 #define LCR_DLAB 0x80
 
-static struct NS16550 __iomem *udbg_comport;
+static u8 (*udbg_uart_in)(unsigned int reg);
+static void (*udbg_uart_out)(unsigned int reg, u8 data);
 
-static void udbg_550_flush(void)
+static void udbg_uart_flush(void)
 {
-	if (udbg_comport) {
-		while ((in_8(&udbg_comport->lsr) & LSR_THRE) == 0)
-			/* wait for idle */;
-	}
+	if (!udbg_uart_in)
+		return;
+
+	/* wait for idle */
+	while ((udbg_uart_in(UART_LSR) & LSR_THRE) == 0)
+		cpu_relax();
 }
 
-static void udbg_550_putc(char c)
+static void udbg_uart_putc(char c)
 {
-	if (udbg_comport) {
+	if (!udbg_uart_out)
+		return;
+
 	if (c == '\n')
-			udbg_550_putc('\r');
-		udbg_550_flush();
-		out_8(&udbg_comport->thr, c);
-	}
+		udbg_uart_putc('\r');
+	udbg_uart_flush();
+	udbg_uart_out(UART_THR, c);
 }
 
-static int udbg_550_getc_poll(void)
+static int udbg_uart_getc_poll(void)
 {
-	if (udbg_comport) {
-		if ((in_8(&udbg_comport->lsr) & LSR_DR) != 0)
-			return in_8(&udbg_comport->rbr);
-		else
-			return -1;
-	}
+	if (!udbg_uart_in || !(udbg_uart_in(UART_LSR) & LSR_DR))
+		return udbg_uart_in(UART_RBR);
 	return -1;
 }
 
-static int udbg_550_getc(void)
+static int udbg_uart_getc(void)
 {
-	if (udbg_comport) {
-		while ((in_8(&udbg_comport->lsr) & LSR_DR) == 0)
-			/* wait for char */;
-		return in_8(&udbg_comport->rbr);
-	}
+	if (!udbg_uart_in)
 		return -1;
+	/* wait for char */
+	while (!(udbg_uart_in(UART_LSR) & LSR_DR))
+		cpu_relax();
+	return udbg_uart_in(UART_RBR);
+}
+
+static void udbg_use_uart(void)
+{
+	udbg_putc = udbg_uart_putc;
+	udbg_flush = udbg_uart_flush;
+	udbg_getc = udbg_uart_getc;
+	udbg_getc_poll = udbg_uart_getc_poll;
 }
 
-void udbg_init_uart(void __iomem *comport, unsigned int speed,
-		    unsigned int clock)
+void udbg_uart_setup(unsigned int speed, unsigned int clock)
 {
 	unsigned int dll, base_bauds;
 
+	if (!udbg_uart_out)
+		return;
+
 	if (clock == 0)
 		clock = 1843200;
 	if (speed == 0)
@@ -101,51 +107,43 @@ void udbg_init_uart(void __iomem *comport, unsigned int speed,
 	base_bauds = clock / 16;
 	dll = base_bauds / speed;
 
-	if (comport) {
-		udbg_comport = (struct NS16550 __iomem *)comport;
-		out_8(&udbg_comport->lcr, 0x00);
-		out_8(&udbg_comport->ier, 0xff);
-		out_8(&udbg_comport->ier, 0x00);
-		out_8(&udbg_comport->lcr, LCR_DLAB);
-		out_8(&udbg_comport->dll, dll & 0xff);
-		out_8(&udbg_comport->dlm, dll >> 8);
+	udbg_uart_out(UART_LCR, 0x00);
+	udbg_uart_out(UART_IER, 0xff);
+	udbg_uart_out(UART_IER, 0x00);
+	udbg_uart_out(UART_LCR, LCR_DLAB);
+	udbg_uart_out(UART_DLL, dll & 0xff);
+	udbg_uart_out(UART_DLM, dll >> 8);
 	/* 8 data, 1 stop, no parity */
-		out_8(&udbg_comport->lcr, 0x03);
+	udbg_uart_out(UART_LCR, 0x3);
 	/* RTS/DTR */
-		out_8(&udbg_comport->mcr, 0x03);
+	udbg_uart_out(UART_MCR, 0x3);
 	/* Clear & enable FIFOs */
-		out_8(&udbg_comport->fcr ,0x07);
-		udbg_putc = udbg_550_putc;
-		udbg_flush = udbg_550_flush;
-		udbg_getc = udbg_550_getc;
-		udbg_getc_poll = udbg_550_getc_poll;
-	}
+	udbg_uart_out(UART_FCR, 0x7);
 }
 
-unsigned int udbg_probe_uart_speed(void __iomem *comport, unsigned int clock)
+unsigned int udbg_probe_uart_speed(unsigned int clock)
 {
 	unsigned int dll, dlm, divisor, prescaler, speed;
 	u8 old_lcr;
-	struct NS16550 __iomem *port = comport;
 
-	old_lcr = in_8(&port->lcr);
+	old_lcr = udbg_uart_in(UART_LCR);
 
 	/* select divisor latch registers.  */
-	out_8(&port->lcr, LCR_DLAB);
+	udbg_uart_out(UART_LCR, old_lcr | LCR_DLAB);
 
 	/* now, read the divisor */
-	dll = in_8(&port->dll);
-	dlm = in_8(&port->dlm);
+	dll = udbg_uart_in(UART_DLL);
+	dlm = udbg_uart_in(UART_DLM);
 	divisor = dlm << 8 | dll;
 
 	/* check prescaling */
-	if (in_8(&port->mcr) & 0x80)
+	if (udbg_uart_in(UART_MCR) & 0x80)
 		prescaler = 4;
 	else
 		prescaler = 1;
 
 	/* restore the LCR */
-	out_8(&port->lcr, old_lcr);
+	udbg_uart_out(UART_LCR, old_lcr);
 
 	/* calculate speed */
 	speed = (clock / prescaler) / (divisor * 16);
@@ -157,150 +155,151 @@ unsigned int udbg_probe_uart_speed(void __iomem *comport, unsigned int clock)
 	return speed;
 }
 
-#ifdef CONFIG_PPC_MAPLE
-void udbg_maple_real_flush(void)
+static union {
+	unsigned char __iomem *mmio_base;
+	unsigned long pio_base;
+} udbg_uart;
+
+static unsigned int udbg_uart_stride = 1;
+
+static u8 udbg_uart_in_pio(unsigned int reg)
 {
-	if (udbg_comport) {
-		while ((real_readb(&udbg_comport->lsr) & LSR_THRE) == 0)
-			/* wait for idle */;
-	}
+	return inb(udbg_uart.pio_base + (reg * udbg_uart_stride));
 }
 
-void udbg_maple_real_putc(char c)
+static void udbg_uart_out_pio(unsigned int reg, u8 data)
 {
-	if (udbg_comport) {
-		if (c == '\n')
-			udbg_maple_real_putc('\r');
-		udbg_maple_real_flush();
-		real_writeb(c, &udbg_comport->thr); eieio();
-	}
+	outb(data, udbg_uart.pio_base + (reg * udbg_uart_stride));
 }
 
-void __init udbg_init_maple_realmode(void)
+void udbg_uart_init_pio(unsigned long port, unsigned int stride)
 {
-	udbg_comport = (struct NS16550 __iomem *)0xf40003f8;
+	if (!port)
+		return;
+	udbg_uart.pio_base = port;
+	udbg_uart_stride = stride;
+	udbg_uart_in = udbg_uart_in_pio;
+	udbg_uart_out = udbg_uart_out_pio;
+	udbg_use_uart();
+}
 
-	udbg_putc = udbg_maple_real_putc;
-	udbg_flush = udbg_maple_real_flush;
-	udbg_getc = NULL;
-	udbg_getc_poll = NULL;
+static u8 udbg_uart_in_mmio(unsigned int reg)
+{
+	return in_8(udbg_uart.mmio_base + (reg * udbg_uart_stride));
 }
-#endif /* CONFIG_PPC_MAPLE */
 
-#ifdef CONFIG_PPC_PASEMI
-void udbg_pas_real_flush(void)
+static void udbg_uart_out_mmio(unsigned int reg, u8 data)
 {
-	if (udbg_comport) {
-		while ((real_205_readb(&udbg_comport->lsr) & LSR_THRE) == 0)
-			/* wait for idle */;
-	}
+	out_8(udbg_uart.mmio_base + (reg * udbg_uart_stride), data);
+}
+
+
+void udbg_uart_init_mmio(void __iomem *addr, unsigned int stride)
+{
+	if (!addr)
+		return;
+	udbg_uart.mmio_base = addr;
+	udbg_uart_stride = stride;
+	udbg_uart_in = udbg_uart_in_mmio;
+	udbg_uart_out = udbg_uart_out_mmio;
+	udbg_use_uart();
 }
 
-void udbg_pas_real_putc(char c)
+#ifdef CONFIG_PPC_MAPLE
+
+#define UDBG_UART_MAPLE_ADDR	((void __iomem *)0xf40003f8)
+
+static u8 udbg_uart_in_maple(unsigned int reg)
 {
-	if (udbg_comport) {
-		if (c == '\n')
-			udbg_pas_real_putc('\r');
-		udbg_pas_real_flush();
-		real_205_writeb(c, &udbg_comport->thr); eieio();
-	}
+	return real_readb(UDBG_UART_MAPLE_ADDR + reg);
 }
 
-void udbg_init_pas_realmode(void)
+static void udbg_uart_out_maple(unsigned int reg, u8 val)
 {
-	udbg_comport = (struct NS16550 __iomem *)0xfcff03f8UL;
+	real_writeb(val, UDBG_UART_MAPLE_ADDR + reg);
+}
 
-	udbg_putc = udbg_pas_real_putc;
-	udbg_flush = udbg_pas_real_flush;
-	udbg_getc = NULL;
-	udbg_getc_poll = NULL;
+void __init udbg_init_maple_realmode(void)
+{
+	udbg_uart_in = udbg_uart_in_maple;
+	udbg_uart_out = udbg_uart_out_maple;
+	udbg_use_uart();
 }
+
 #endif /* CONFIG_PPC_MAPLE */
 
-#ifdef CONFIG_PPC_EARLY_DEBUG_44x
-#include <platforms/44x/44x.h>
+#ifdef CONFIG_PPC_PASEMI
+
+#define UDBG_UART_PAS_ADDR	((void __iomem *)0xfcff03f8UL)
 
-static void udbg_44x_as1_flush(void)
+static u8 udbg_uart_in_pas(unsigned int reg)
 {
-	if (udbg_comport) {
-		while ((as1_readb(&udbg_comport->lsr) & LSR_THRE) == 0)
-			/* wait for idle */;
-	}
+	return real_205_readb(UDBG_UART_PAS_ADDR + reg);
 }
 
-static void udbg_44x_as1_putc(char c)
+static void udbg_uart_out_pas(unsigned int reg, u8 val)
 {
-	if (udbg_comport) {
-		if (c == '\n')
-			udbg_44x_as1_putc('\r');
-		udbg_44x_as1_flush();
-		as1_writeb(c, &udbg_comport->thr); eieio();
-	}
+	real_205_writeb(val, UDBG_UART_PAS_ADDR + reg);
 }
 
-static int udbg_44x_as1_getc(void)
+void __init udbg_init_pas_realmode(void)
 {
-	if (udbg_comport) {
-		while ((as1_readb(&udbg_comport->lsr) & LSR_DR) == 0)
-			; /* wait for char */
-		return as1_readb(&udbg_comport->rbr);
-	}
-	return -1;
+	udbg_uart_in = udbg_uart_in_pas;
+	udbg_uart_out = udbg_uart_out_pas;
+	udbg_use_uart();
 }
 
-void __init udbg_init_44x_as1(void)
+#endif /* CONFIG_PPC_PASEMI */
+
+#ifdef CONFIG_PPC_EARLY_DEBUG_44x
+
+#include <platforms/44x/44x.h>
+
+static u8 udbg_uart_in_44x_as1(unsigned int reg)
 {
-	udbg_comport =
-		(struct NS16550 __iomem *)PPC44x_EARLY_DEBUG_VIRTADDR;
+	return as1_readb((void __iomem *)PPC44x_EARLY_DEBUG_VIRTADDR + reg);
+}
 
-	udbg_putc = udbg_44x_as1_putc;
-	udbg_flush = udbg_44x_as1_flush;
-	udbg_getc = udbg_44x_as1_getc;
+static void udbg_uart_out_44x_as1(unsigned int reg, u8 val)
+{
+	as1_writeb(val, (void __iomem *)PPC44x_EARLY_DEBUG_VIRTADDR + reg);
 }
-#endif /* CONFIG_PPC_EARLY_DEBUG_44x */
 
-#ifdef CONFIG_PPC_EARLY_DEBUG_40x
-static void udbg_40x_real_flush(void)
+void __init udbg_init_44x_as1(void)
 {
-	if (udbg_comport) {
-		while ((real_readb(&udbg_comport->lsr) & LSR_THRE) == 0)
-			/* wait for idle */;
-	}
+	udbg_uart_in = udbg_uart_in_44x_as1;
+	udbg_uart_out = udbg_uart_out_44x_as1;
+	udbg_use_uart();
 }
 
-static void udbg_40x_real_putc(char c)
+#endif /* CONFIG_PPC_EARLY_DEBUG_44x */
+
+#ifdef CONFIG_PPC_EARLY_DEBUG_40x
+
+static u8 udbg_uart_in_40x(unsigned int reg)
 {
-	if (udbg_comport) {
-		if (c == '\n')
-			udbg_40x_real_putc('\r');
-		udbg_40x_real_flush();
-		real_writeb(c, &udbg_comport->thr); eieio();
-	}
+	return real_readb((void __iomem *)CONFIG_PPC_EARLY_DEBUG_40x_PHYSADDR
+			  + reg);
 }
 
-static int udbg_40x_real_getc(void)
+static void udbg_uart_out_40x(unsigned int reg, u8 val)
 {
-	if (udbg_comport) {
-		while ((real_readb(&udbg_comport->lsr) & LSR_DR) == 0)
-			; /* wait for char */
-		return real_readb(&udbg_comport->rbr);
-	}
-	return -1;
+	real_writeb(val, (void __iomem *)CONFIG_PPC_EARLY_DEBUG_40x_PHYSADDR
+		    + reg);
 }
 
 void __init udbg_init_40x_realmode(void)
 {
-	udbg_comport = (struct NS16550 __iomem *)
-		CONFIG_PPC_EARLY_DEBUG_40x_PHYSADDR;
-
-	udbg_putc = udbg_40x_real_putc;
-	udbg_flush = udbg_40x_real_flush;
-	udbg_getc = udbg_40x_real_getc;
-	udbg_getc_poll = NULL;
+	udbg_uart_in = udbg_uart_in_40x;
+	udbg_uart_out = udbg_uart_out_40x;
+	udbg_use_uart();
 }
+
 #endif /* CONFIG_PPC_EARLY_DEBUG_40x */
 
+
 #ifdef CONFIG_PPC_EARLY_DEBUG_WSP
+
 static void udbg_wsp_flush(void)
 {
 	if (udbg_comport) {
@@ -339,13 +338,8 @@ static int udbg_wsp_getc_poll(void)
 
 void __init udbg_init_wsp(void)
 {
-	udbg_comport = (struct NS16550 __iomem *)WSP_UART_VIRT;
-
-	udbg_init_uart(udbg_comport, 57600, 50000000);
-
-	udbg_putc = udbg_wsp_putc;
-	udbg_flush = udbg_wsp_flush;
-	udbg_getc = udbg_wsp_getc;
-	udbg_getc_poll = udbg_wsp_getc_poll;
+	udbg_uart_init_mmio(WSP_UART_VIRT, 1);
+	udbg_uart_setup(57600, 50000000);
 }
+
 #endif /* CONFIG_PPC_EARLY_DEBUG_WSP */