arch/x86/kernel/io_delay.c

   1 /*
   2  * I/O delay strategies for inb_p/outb_p
   3  *
   4  * Allow for a DMI based override of port 0x80, needed for certain HP laptops
   5  * and possibly other systems. Also allow for the gradual elimination of
   6  * outb_p/inb_p API uses.
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/module.h>
  10 #include <linux/init.h>
  11 #include <linux/delay.h>
  12 #include <linux/dmi.h>
  13 #include <asm/io.h>
  14
  15 int io_delay_type __read_mostly = CONFIG_DEFAULT_IO_DELAY_TYPE;
  16 EXPORT_SYMBOL_GPL(io_delay_type);
  17
  18 static int __initdata io_delay_override;
  19
  20 /*
  21  * Paravirt wants native_io_delay to be a constant.
  22  */
  23 void native_io_delay(void)
  24 {
  25         switch (io_delay_type) {
  26         default:
  27         case CONFIG_IO_DELAY_TYPE_0X80:
  28                 asm volatile ("outb %al, $0x80");
  29                 break;
  30         case CONFIG_IO_DELAY_TYPE_0XED:
  31                 asm volatile ("outb %al, $0xed");
  32                 break;
  33         case CONFIG_IO_DELAY_TYPE_UDELAY:
  34                 /*
  35                  * 2 usecs is an upper-bound for the outb delay but
  36                  * note that udelay doesn't have the bus-level
  37                  * side-effects that outb does, nor does udelay() have
  38                  * precise timings during very early bootup (the delays
  39                  * are shorter until calibrated):
  40                  */
  41                 udelay(2);
  42         case CONFIG_IO_DELAY_TYPE_NONE:
  43                 break;
  44         }
  45 }
  46 EXPORT_SYMBOL(native_io_delay);
  47
  48 static int __init dmi_io_delay_0xed_port(const struct dmi_system_id *id)
  49 {
  50         if (io_delay_type == CONFIG_IO_DELAY_TYPE_0X80) {
  51                 printk(KERN_NOTICE "%s: using 0xed I/O delay port\n",
  52                         id->ident);
  53                 io_delay_type = CONFIG_IO_DELAY_TYPE_0XED;
  54         }
  55
  56         return 0;
  57 }
  58
  59 /*
  60  * Quirk table for systems that misbehave (lock up, etc.) if port
  61  * 0x80 is used:
  62  */
  63 static struct dmi_system_id __initdata io_delay_0xed_port_dmi_table[] = {
  64         {
  65                 .callback       = dmi_io_delay_0xed_port,
  66                 .ident          = "HP Pavilion dv9000z",
  67                 .matches        = {
  68                         DMI_MATCH(DMI_BOARD_VENDOR, "Quanta"),
  69                         DMI_MATCH(DMI_BOARD_NAME, "30B9")
  70                 }
  71         },
  72         { }
  73 };
  74
  75 void __init io_delay_init(void)
  76 {
  77         if (!io_delay_override)
  78                 dmi_check_system(io_delay_0xed_port_dmi_table);
  79 }
  80
  81 static int __init io_delay_param(char *s)
  82 {
  83         if (!strcmp(s, "0x80"))
  84                 io_delay_type = CONFIG_IO_DELAY_TYPE_0X80;
  85         else if (!strcmp(s, "0xed"))
  86                 io_delay_type = CONFIG_IO_DELAY_TYPE_0XED;
  87         else if (!strcmp(s, "udelay"))
  88                 io_delay_type = CONFIG_IO_DELAY_TYPE_UDELAY;
  89         else if (!strcmp(s, "none"))
  90                 io_delay_type = CONFIG_IO_DELAY_TYPE_NONE;
  91         else
  92                 return -EINVAL;
  93
  94         io_delay_override = 1;
  95         return 0;
  96 }
  97
  98 early_param("io_delay", io_delay_param);