[PATCH v2 2/7] x86/boot: Introduce helpers for serial I/O

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

As preparatory to enable earlyprintk on non-standard ports on x86,
introduce serial_in() and serial_out() helpers to perform serial I/O.

No functional change intended.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 arch/x86/boot/boot.h                          |  2 +
 .../boot/compressed/early_serial_console.c    |  3 +
 arch/x86/boot/compressed/misc.c               |  4 +-
 arch/x86/boot/compressed/misc.h               |  4 ++
 arch/x86/boot/early_serial_console.c          | 63 +++++++++++++------
 arch/x86/boot/tty.c                           |  7 ++-
 6 files changed, 61 insertions(+), 22 deletions(-)

diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index f41291903da7..86641b2e83f8 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -299,6 +299,8 @@ int check_knl_erratum(void);
 int validate_cpu(void);
 
 /* early_serial_console.c */
+extern unsigned int (*serial_in)(unsigned long addr, int offset);
+extern void (*serial_out)(unsigned long addr, int offset, int value);
 extern unsigned long early_serial_base;
 void console_init(void);
 
diff --git a/arch/x86/boot/compressed/early_serial_console.c b/arch/x86/boot/compressed/early_serial_console.c
index 5e3a66478754..4b6269624b59 100644
--- a/arch/x86/boot/compressed/early_serial_console.c
+++ b/arch/x86/boot/compressed/early_serial_console.c
@@ -1,5 +1,8 @@
 #include "misc.h"
 
+unsigned int (*serial_in)(unsigned long addr, int offset);
+void (*serial_out)(unsigned long addr, int offset, int value);
+
 unsigned long early_serial_base;
 
 #include "../early_serial_console.c"
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index c0d6c560df69..75b3c8bb92ac 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -98,10 +98,10 @@ static void serial_putchar(int ch)
 {
 	unsigned timeout = 0xffff;
 
-	while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
+	while ((serial_in(early_serial_base, LSR) & XMTRDY) == 0 && --timeout)
 		cpu_relax();
 
-	outb(ch, early_serial_base + TXR);
+	serial_out(early_serial_base, TXR, ch);
 }
 
 void __putstr(const char *s)
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 6f2bdf813949..2fd3ec89a70d 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -110,9 +110,13 @@ static inline void finalize_identity_maps(void)
 
 #ifdef CONFIG_EARLY_PRINTK
 /* early_serial_console.c */
+extern unsigned int (*serial_in)(unsigned long addr, int offset);
+extern void (*serial_out)(unsigned long addr, int offset, int value);
 extern unsigned long early_serial_base;
 void console_init(void);
 #else
+static unsigned int (*serial_in)(unsigned long addr, int offset);
+static void (*serial_out)(unsigned long addr, int offset, int value);
 static const unsigned long early_serial_base;
 static inline void console_init(void)
 { }
diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c
index 2b663beda582..05d02cd4de99 100644
--- a/arch/x86/boot/early_serial_console.c
+++ b/arch/x86/boot/early_serial_console.c
@@ -23,22 +23,45 @@
 
 #define DEFAULT_BAUD 9600
 
-static void early_serial_init(unsigned long port, int baud)
+static unsigned int io_serial_in(unsigned long addr, int offset)
+{
+	return inb(addr + offset);
+}
+
+static void io_serial_out(unsigned long addr, int offset, int value)
+{
+	outb(value, addr + offset);
+}
+
+static void early_serial_configure(unsigned long port, int baud)
 {
 	unsigned char c;
 	unsigned divisor;
 
-	outb(0x3, port + LCR);	/* 8n1 */
-	outb(0, port + IER);	/* no interrupt */
-	outb(0, port + FCR);	/* no fifo */
-	outb(0x3, port + MCR);	/* DTR + RTS */
+	serial_out(port, LCR, 0x3);	/* 8n1 */
+	serial_out(port, IER, 0);	/* no interrupt */
+	serial_out(port, FCR, 0);	/* no fifo */
+	serial_out(port, MCR, 0x3);	/* DTR + RTS */
 
 	divisor	= 115200 / baud;
-	c = inb(port + LCR);
-	outb(c | DLAB, port + LCR);
-	outb(divisor & 0xff, port + DLL);
-	outb((divisor >> 8) & 0xff, port + DLH);
-	outb(c & ~DLAB, port + LCR);
+	c = serial_in(port, LCR);
+	serial_out(port, LCR, c | DLAB);
+	serial_out(port, DLL, divisor & 0xff);
+	serial_out(port, DLH, (divisor >> 8) & 0xff);
+	serial_out(port, LCR, c & ~DLAB);
+}
+
+/* Assign serial I/O accessors */
+static void early_serial_use_io_accessors(void)
+{
+	/* These will always be IO based ports */
+	serial_in = io_serial_in;
+	serial_out = io_serial_out;
+}
+
+static void early_serial_init(unsigned long port, int baud)
+{
+	early_serial_configure(port, baud);
 
 	early_serial_base = port;
 }
@@ -73,6 +96,7 @@ static void parse_earlyprintk(void)
 				port = DEFAULT_SERIAL_PORT;
 			else
 				pos = e - arg;
+			early_serial_use_io_accessors();
 		} else if (!strncmp(arg + pos, "ttyS", 4)) {
 			static const int bases[] = { 0x3f8, 0x2f8 };
 			int idx = 0;
@@ -84,6 +108,7 @@ static void parse_earlyprintk(void)
 				idx = 1;
 
 			port = bases[idx];
+			early_serial_use_io_accessors();
 		}
 
 		if (arg[pos] == ',')
@@ -104,11 +129,11 @@ static unsigned int probe_baud(int port)
 	unsigned char lcr, dll, dlh;
 	unsigned int quot;
 
-	lcr = inb(port + LCR);
-	outb(lcr | DLAB, port + LCR);
-	dll = inb(port + DLL);
-	dlh = inb(port + DLH);
-	outb(lcr, port + LCR);
+	lcr = serial_in(port, LCR);
+	serial_out(port, LCR, lcr | DLAB);
+	dll = serial_in(port, DLL);
+	dlh = serial_in(port, DLH);
+	serial_out(port, LCR, lcr);
 	quot = (dlh << 8) | dll;
 
 	return BASE_BAUD / quot;
@@ -129,11 +154,13 @@ static void parse_console_uart8250(void)
 
 	options = optstr;
 
-	if (!strncmp(options, "uart8250,io,", 12))
+	if (!strncmp(options, "uart8250,io,", 12)) {
 		port = simple_strtoull(options + 12, &options, 0);
-	else if (!strncmp(options, "uart,io,", 8))
+		early_serial_use_io_accessors();
+	} else if (!strncmp(options, "uart,io,", 8)) {
 		port = simple_strtoull(options + 8, &options, 0);
-	else
+		early_serial_use_io_accessors();
+	} else
 		return;
 
 	if (options && (options[0] == ','))
diff --git a/arch/x86/boot/tty.c b/arch/x86/boot/tty.c
index d1d34c6ca153..b6aa9db65cda 100644
--- a/arch/x86/boot/tty.c
+++ b/arch/x86/boot/tty.c
@@ -15,6 +15,9 @@
 
 #include "boot.h"
 
+unsigned int (*serial_in)(unsigned long addr, int offset);
+void (*serial_out)(unsigned long addr, int offset, int value);
+
 unsigned long early_serial_base;
 
 #define XMTRDY          0x20
@@ -31,10 +34,10 @@ static void __attribute__((section(".inittext"))) serial_putchar(int ch)
 {
 	unsigned timeout = 0xffff;
 
-	while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
+	while ((serial_in(early_serial_base, LSR) & XMTRDY) == 0 && --timeout)
 		cpu_relax();
 
-	outb(ch, early_serial_base + TXR);
+	serial_out(early_serial_base, TXR, ch);
 }
 
 static void __attribute__((section(".inittext"))) bios_putchar(int ch)
-- 
2.20.1