On 18-02-08 19:58, David P. Reed wrote:
--- linux-2.6.orig/include/asm-x86/i8253.h
+++ linux-2.6/include/asm-x86/i8253.h
@@ -12,7 +12,25 @@ extern struct clock_event_device *global
extern void setup_pit_timer(void);
-#define inb_pit inb_p
-#define outb_pit outb_p
+/* accesses to PIT registers need careful delays on some platforms. Define
+ them here in a common place */
+static inline unsigned char inb_pit(unsigned int port)
+{
+ /* delay for some accesses to PIT on motherboard or in chipset must be
+ at least one microsecond, but be safe here. */
+ unsigned char value = inb(port);
+ udelay(2);
+ return value;
+}
With the remark that (at least) the PIT is accessed at a time that
microseconds and hence udelay are still a total fiction, this looks obvious
otherwise.
Now with respect to the original pre port 80 "jmp $+2" I/O delay (which the
Pentium obsoleted) I suppose it'll probably be okay even without fixing that
specifically but do note such -- it's a vital part of the problem.
Rene.
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