From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Ashish Kalra <ashish.kalra@amd.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
linux-kernel@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
David Woodhouse <dwmw@amazon.co.uk>,
Denis Mukhin <dmukhin@ford.com>
Subject: [PATCH v1 2/6] x86/boot: Introduce helpers for serial I/O
Date: Fri, 2 May 2025 15:29:38 +0300 [thread overview]
Message-ID: <20250502123145.4066635-3-andriy.shevchenko@linux.intel.com> (raw)
In-Reply-To: <20250502123145.4066635-1-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 753f429b28cb..6688c2053707 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -274,6 +274,8 @@ 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 5b8db03f40ad..a5e0459c3d2f 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);
+
/* This might be accessed before .bss is cleared, so use .data instead. */
unsigned long early_serial_base __section(".data");
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 94b5991da001..056fa5f01598 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -109,10 +109,10 @@ 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 f083360c84c1..a70e5f31765b 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -127,9 +127,13 @@ extern unsigned char _pgtable[];
#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 7a7766fa16e5..f52a14284854 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 e2ab8b8076ef..eb0eacd88db7 100644
--- a/arch/x86/boot/tty.c
+++ b/arch/x86/boot/tty.c
@@ -13,6 +13,9 @@
#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
@@ -29,10 +32,10 @@ static void __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 __section(".inittext") bios_putchar(int ch)
--
2.47.2
next prev parent reply other threads:[~2025-05-02 12:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-02 12:29 [PATCH v1 0/6] x86/boot: Enable earlyprintk on MMIO (8-bit) Andy Shevchenko
2025-05-02 12:29 ` [PATCH v1 1/6] x86/boot: Convert early_serial_base to unsigned long Andy Shevchenko
2025-05-02 12:29 ` Andy Shevchenko [this message]
2025-05-02 12:29 ` [PATCH v1 3/6] x86/boot: Split out parse_serial_port() helper for earlyprintk Andy Shevchenko
2025-05-02 12:29 ` [PATCH v1 4/6] x86/boot: Allow longer parameter list " Andy Shevchenko
2025-05-02 12:29 ` [PATCH v1 5/6] x86/boot: Also share MMIO accessors Andy Shevchenko
2025-05-02 12:29 ` [PATCH v1 6/6] x86/boot: Introduce MMIO accessors and their support in earlyprintk Andy Shevchenko
2025-05-02 17:33 ` [PATCH v1 0/6] x86/boot: Enable earlyprintk on MMIO (8-bit) David Woodhouse
2025-05-05 14:05 ` Andy Shevchenko
2025-05-05 14:35 ` David Woodhouse
2025-05-05 14:59 ` Andy Shevchenko
2025-05-05 15:01 ` Andy Shevchenko
2025-05-05 23:32 ` David Woodhouse
2025-05-06 3:19 ` David Woodhouse
2025-05-06 19:38 ` David Woodhouse
2025-05-07 13:54 ` Andy Shevchenko
-- strict thread matches above, loose matches on Subject: below --
2018-01-14 14:32 [PATCH v1 1/6] x86/boot: Convert early_serial_base to unsigned long Andy Shevchenko
2018-01-14 14:32 ` [PATCH v1 2/6] x86/boot: Introduce helpers for serial I/O Andy Shevchenko
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