x86: various changes and cleanups to in_p/out_p delay details

various changes to the in_p/out_p delay details:

- add the io_delay=none method
- make each method selectable from the kernel config
- simplify the delay code a bit by getting rid of an indirect function call
- add the /proc/sys/kernel/io_delay_type sysctl
- change 'io_delay=standard|alternate' to io_delay=0x80 and io_delay=0xed
- make the io delay config not depend on CONFIG_DEBUG_KERNEL

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: "David P. Reed" <dpreed@reed.com>

2 files changed, 121 insertions, 64 deletions

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 40aba670fb37..77eda46f97b8 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -112,13 +112,78 @@ config IOMMU_LEAK
           Add a simple leak tracer to the IOMMU code. This is useful when you
           are debugging a buggy device driver that leaks IOMMU mappings.
 
-config UDELAY_IO_DELAY
-        bool "Delay I/O through udelay instead of outb"
-        depends on DEBUG_KERNEL
+#
+# IO delay types:
+#
+
+config IO_DELAY_TYPE_0X80
+        int
+        default "0"
+
+config IO_DELAY_TYPE_0XED
+        int
+        default "1"
+
+config IO_DELAY_TYPE_UDELAY
+        int
+        default "2"
+
+config IO_DELAY_TYPE_NONE
+        int
+        default "3"
+
+choice
+        prompt "IO delay type"
+        default IO_DELAY_0X80
+
+config IO_DELAY_0X80
+        bool "port 0x80 based port-IO delay [recommended]"
+        help
+          This is the traditional Linux IO delay used for in/out_p.
+          It is the most tested hence safest selection here.
+
+config IO_DELAY_0XED
+        bool "port 0xed based port-IO delay"
+        help
+          Use port 0xed as the IO delay. This frees up port 0x80 which is
+          often used as a hardware-debug port.
+
+config IO_DELAY_UDELAY
+        bool "udelay based port-IO delay"
+        help
+          Use udelay(2) as the IO delay method. This provides the delay
+          while not having any side-effect on the IO port space.
+
+config IO_DELAY_NONE
+        bool "no port-IO delay"
         help
-          Make inb_p/outb_p use udelay() based delays by default. Please note
-          that udelay() does not have the same bus-level side-effects that
-          the normal outb based delay does meaning this could cause drivers
-          to change behaviour and/or bugs to surface.
+          No port-IO delay. Will break on old boxes that require port-IO
+          delay for certain operations. Should work on most new machines.
+
+endchoice
+
+if IO_DELAY_0X80
+config DEFAULT_IO_DELAY_TYPE
+        int
+        default IO_DELAY_TYPE_0X80
+endif
+
+if IO_DELAY_0XED
+config DEFAULT_IO_DELAY_TYPE
+        int
+        default IO_DELAY_TYPE_0XED
+endif
+
+if IO_DELAY_UDELAY
+config DEFAULT_IO_DELAY_TYPE
+        int
+        default IO_DELAY_TYPE_UDELAY
+endif
+
+if IO_DELAY_NONE
+config DEFAULT_IO_DELAY_TYPE
+        int
+        default IO_DELAY_TYPE_NONE
+endif
 
 endmenu
diff --git a/arch/x86/kernel/io_delay.c b/arch/x86/kernel/io_delay.c
index 4d955e74b974..f052e34dc94c 100644
--- a/arch/x86/kernel/io_delay.c
+++ b/arch/x86/kernel/io_delay.c
@@ -1,5 +1,9 @@
 /*
  * I/O delay strategies for inb_p/outb_p
+ *
+ * Allow for a DMI based override of port 0x80, needed for certain HP laptops
+ * and possibly other systems. Also allow for the gradual elimination of
+ * outb_p/inb_p API uses.
  */
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -8,98 +12,86 @@
 #include <linux/dmi.h>
 #include <asm/io.h>
 
-/*
- * Allow for a DMI based override of port 0x80 needed for certain HP laptops
- */
-#define IO_DELAY_PORT_STD 0x80
-#define IO_DELAY_PORT_ALT 0xed
-
-static void standard_io_delay(void)
-{
-        asm volatile ("outb %%al, %0" : : "N" (IO_DELAY_PORT_STD));
-}
-
-static void alternate_io_delay(void)
-{
-        asm volatile ("outb %%al, %0" : : "N" (IO_DELAY_PORT_ALT));
-}
-
-/*
- * 2 usecs is an upper-bound for the outb delay but note that udelay doesn't
- * have the bus-level side-effects that outb does
- */
-#define IO_DELAY_USECS 2
-
-/*
- * High on a hill was a lonely goatherd
- */
-static void udelay_io_delay(void)
-{
-        udelay(IO_DELAY_USECS);
-}
+int io_delay_type __read_mostly = CONFIG_DEFAULT_IO_DELAY_TYPE;
+EXPORT_SYMBOL_GPL(io_delay_type);
 
-#ifndef CONFIG_UDELAY_IO_DELAY
-static void (*io_delay)(void) = standard_io_delay;
-#else
-static void (*io_delay)(void) = udelay_io_delay;
-#endif
+static int __initdata io_delay_override;
 
 /*
  * Paravirt wants native_io_delay to be a constant.
  */
 void native_io_delay(void)
 {
-        io_delay();
+        switch (io_delay_type) {
+        default:
+        case CONFIG_IO_DELAY_TYPE_0X80:
+                asm volatile ("outb %al, $0x80");
+                break;
+        case CONFIG_IO_DELAY_TYPE_0XED:
+                asm volatile ("outb %al, $0xed");
+                break;
+        case CONFIG_IO_DELAY_TYPE_UDELAY:
+                /*
+                 * 2 usecs is an upper-bound for the outb delay but
+                 * note that udelay doesn't have the bus-level
+                 * side-effects that outb does, nor does udelay() have
+                 * precise timings during very early bootup (the delays
+                 * are shorter until calibrated):
+                 */
+                udelay(2);
+        case CONFIG_IO_DELAY_TYPE_NONE:
+                break;
+        }
 }
 EXPORT_SYMBOL(native_io_delay);
 
-#ifndef CONFIG_UDELAY_IO_DELAY
-static int __init dmi_alternate_io_delay_port(const struct dmi_system_id *id)
+static int __init dmi_io_delay_0xed_port(const struct dmi_system_id *id)
 {
-        printk(KERN_NOTICE "%s: using alternate I/O delay port\n", id->ident);
-        io_delay = alternate_io_delay;
+        if (io_delay_type == CONFIG_IO_DELAY_TYPE_0X80) {
+                printk(KERN_NOTICE "%s: using 0xed I/O delay port\n",
+                        id->ident);
+                io_delay_type = CONFIG_IO_DELAY_TYPE_0XED;
+        }
+
         return 0;
 }
 
-static struct dmi_system_id __initdata alternate_io_delay_port_dmi_table[] = {
+/*
+ * Quirk table for systems that misbehave (lock up, etc.) if port
+ * 0x80 is used:
+ */
+static struct dmi_system_id __initdata io_delay_0xed_port_dmi_table[] = {
         {
-                .callback       = dmi_alternate_io_delay_port,
+                .callback       = dmi_io_delay_0xed_port,
                 .ident          = "HP Pavilion dv9000z",
                 .matches        = {
                         DMI_MATCH(DMI_BOARD_VENDOR, "Quanta"),
                         DMI_MATCH(DMI_BOARD_NAME, "30B9")
                 }
         },
-        {
-        }
+        { }
 };
 
-static int __initdata io_delay_override;
-
 void __init io_delay_init(void)
 {
         if (!io_delay_override)
-                dmi_check_system(alternate_io_delay_port_dmi_table);
+                dmi_check_system(io_delay_0xed_port_dmi_table);
 }
-#endif
 
 static int __init io_delay_param(char *s)
 {
-        if (!s)
-                return -EINVAL;
-
-        if (!strcmp(s, "standard"))
-                io_delay = standard_io_delay;
-        else if (!strcmp(s, "alternate"))
-                io_delay = alternate_io_delay;
+        if (!strcmp(s, "0x80"))
+                io_delay_type = CONFIG_IO_DELAY_TYPE_0X80;
+        else if (!strcmp(s, "0xed"))
+                io_delay_type = CONFIG_IO_DELAY_TYPE_0XED;
         else if (!strcmp(s, "udelay"))
-                io_delay = udelay_io_delay;
+                io_delay_type = CONFIG_IO_DELAY_TYPE_UDELAY;
+        else if (!strcmp(s, "none"))
+                io_delay_type = CONFIG_IO_DELAY_TYPE_NONE;
         else
                 return -EINVAL;
 
-#ifndef CONFIG_UDELAY_IO_DELAY
         io_delay_override = 1;
-#endif
         return 0;
 }