[Linux-parport] [PATCH] parport_pc: after superio probing restore original register values

[Jens Rottmann]

CONFIG_PARPORT_PC_SUPERIO probes for various superio chips by writing
byte sequences to a set of different potential I/O ranges.  But the
probed ranges are not exclusive to parallel ports.  Some of our boards
just happen to have a watchdog in one of them.  Took us almost a week
to figure out why some distros reboot without warning after running
flawlessly for 3 hours.  For exactly 170 = 0xAA minutes, that is ...

Fixed by restoring original values after probing.  Also fixed too small
request_region() in detect_and_report_it87().

Signed-off-by: Jens Rottmann <JRottmann at LiPPERTEmbedded.de>
---

Patch is against Linus' current git tree.

--- linux-2.6.30-git8/drivers/parport/parport_pc.c
+++ conservative-superio-probing/drivers/parport/parport_pc.c
@@ -1471,11 +1471,13 @@ static void __devinit decode_smsc(int ef
 
 static void __devinit winbond_check(int io, int key)
 {
-	int devid, devrev, oldid, x_devid, x_devrev, x_oldid;
+	int origval, devid, devrev, oldid, x_devid, x_devrev, x_oldid;
 
 	if (!request_region(io, 3, __func__))
 		return;
 
+	origval = inb(io); /* Save original value */
+
 	/* First probe without key */
 	outb(0x20, io);
 	x_devid = inb(io + 1);
@@ -1495,6 +1497,8 @@ static void __devinit winbond_check(int 
 	oldid = inb(io + 1);
 	outb(0xaa, io);    /* Magic Seal */
 
+	outb(origval, io); /* in case we poked some entirely different hardware */
+
 	if ((x_devid == devid) && (x_devrev == devrev) && (x_oldid == oldid))
 		goto out; /* protection against false positives */
 
@@ -1505,11 +1509,15 @@ out:
 
 static void __devinit winbond_check2(int io, int key)
 {
-	int devid, devrev, oldid, x_devid, x_devrev, x_oldid;
+	int origval[3], devid, devrev, oldid, x_devid, x_devrev, x_oldid;
 
 	if (!request_region(io, 3, __func__))
 		return;
 
+	origval[0] = inb(io); /* Save original values */
+	origval[1] = inb(io + 1);
+	origval[2] = inb(io + 2);
+
 	/* First probe without the key */
 	outb(0x20, io + 2);
 	x_devid = inb(io + 2);
@@ -1528,6 +1536,10 @@ static void __devinit winbond_check2(int
 	oldid = inb(io + 2);
 	outb(0xaa, io);    /* Magic Seal */
 
+	outb(origval[0], io); /* in case we poked some entirely different hardware */
+	outb(origval[1], io + 1);
+	outb(origval[2], io + 2);
+
 	if (x_devid == devid && x_devrev == devrev && x_oldid == oldid)
 		goto out; /* protection against false positives */
 
@@ -1538,11 +1550,13 @@ out:
 
 static void __devinit smsc_check(int io, int key)
 {
-	int id, rev, oldid, oldrev, x_id, x_rev, x_oldid, x_oldrev;
+	int origval, id, rev, oldid, oldrev, x_id, x_rev, x_oldid, x_oldrev;
 
 	if (!request_region(io, 3, __func__))
 		return;
 
+	origval = inb(io); /* Save original value */
+
 	/* First probe without the key */
 	outb(0x0d, io);
 	x_oldid = inb(io + 1);
@@ -1566,6 +1580,8 @@ static void __devinit smsc_check(int io,
 	rev = inb(io + 1);
 	outb(0xaa, io);    /* Magic Seal */
 
+	outb(origval, io); /* in case we poked some entirely different hardware */
+
 	if (x_id == id && x_oldrev == oldrev &&
 	    x_oldid == oldid && x_rev == rev)
 		goto out; /* protection against false positives */
@@ -1602,11 +1618,12 @@ static void __devinit detect_and_report_
 static void __devinit detect_and_report_it87(void)
 {
 	u16 dev;
-	u8 r;
+	u8 origval, r;
 	if (verbose_probing)
 		printk(KERN_DEBUG "IT8705 Super-IO detection, now testing port 2E ...\n");
-	if (!request_region(0x2e, 1, __func__))
+	if (!request_region(0x2e, 2, __func__))
 		return;
+	origval = inb(0x2e);		/* Save original value */
 	outb(0x87, 0x2e);
 	outb(0x01, 0x2e);
 	outb(0x55, 0x2e);
@@ -1626,8 +1643,10 @@ static void __devinit detect_and_report_
 		outb(r | 8, 0x2F);
 		outb(0x02, 0x2E);	/* Lock */
 		outb(0x02, 0x2F);
+	} else {
+		outb(origval, 0x2e);	/* Oops, sorry to disturb */
 	}
-	release_region(0x2e, 1);
+	release_region(0x2e, 2);
 }
 #endif /* CONFIG_PARPORT_PC_SUPERIO */
 
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