printing on my canon bjc250 was horribly slow. this patch makes printing at acceptible speeds.

Notes:
Fri Jun 12 12:24:20 EDT 2009 geoff
    applied a different fix, as discussed.


Reference: /n/sources/patch/applied/lpt-speedup
Date: Mon Jun  1 21:35:47 CES 2009
Signed-off-by: cinap_lenrek@gmx.de
Reviewed-by: geoff

--- /sys/src/9/pc/devlpt.c	Mon Jun  1 21:35:11 2009
+++ /sys/src/9/pc/devlpt.c	Mon Jun  1 21:35:08 2009
@@ -191,14 +191,19 @@
 static void
 outch(int base, int c)
 {
-	int status, tries;
+	int status, tries, spin;
+	static int maxspin = 0;
 
+	spin = 0;
 	for(tries=0;; tries++) {
 		status = inb(base+Qpsr);
 		if(status&Fnotbusy)
 			break;
 		if((status&Fpe)==0 && (status&(Fselect|Fnoerror)) != (Fselect|Fnoerror))
 			error(Eio);
+		if(++spin < maxspin)
+			continue;
+		maxspin++;
 		if(tries < 10)
 			tsleep(&lptrendez, return0, nil, 1);
 		else {
@@ -209,6 +214,8 @@
 	outb(base+Qdlr, c);
 	outb(base+Qpcr, Finitbar|Fstrobe);
 	outb(base+Qpcr, Finitbar);
+	if(spin*2 + 16 < maxspin)
+		maxspin--;
 }
 
 static int