[PATCH v1 2/6] x86/boot: Introduce helpers for serial I/O

[Andy Shevchenko]

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@xxxxxxxxxxxxxxx>
---
 arch/x86/boot/boot.h                            |  2 +
 arch/x86/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            | 60 +++++++++++++++++--------
 arch/x86/boot/tty.c                             |  7 ++-
 6 files changed, 57 insertions(+), 23 deletions(-)

diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index d9f8279774f6..7e6ac187275c 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 98761a1576ce..0b16675c2523 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -97,10 +97,10 @@ 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 d36d4398a6b0..266e6b93788c 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -101,9 +101,13 @@ 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 a5aec142c91a..8b091919b3b9 100644
--- a/arch/x86/boot/early_serial_console.c
+++ b/arch/x86/boot/early_serial_console.c
@@ -23,22 +23,46 @@
 
 #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);
+}
+
+static void early_serial_init(unsigned long port, int baud)
+{
+	/* Assign serial I/O accessors */
+	if (port) {
+		/* These will always be IO based ports */
+		serial_in = io_serial_in;
+		serial_out = io_serial_out;
+	} else {
+		return;
+	}
+
+	early_serial_configure(port, baud);
 
 	early_serial_base = port;
 }
@@ -94,8 +118,7 @@ static void parse_earlyprintk(void)
 			baud = DEFAULT_BAUD;
 	}
 
-	if (port)
-		early_serial_init(port, baud);
+	early_serial_init(port, baud);
 }
 
 #define BASE_BAUD (1843200/16)
@@ -104,11 +127,11 @@ 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;
@@ -141,8 +164,7 @@ static void parse_console_uart8250(void)
 	else
 		baud = probe_baud(port);
 
-	if (port)
-		early_serial_init(port, baud);
+	early_serial_init(port, baud);
 }
 
 void console_init(void)
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)
-- 
2.15.1