[PATCH] 2.[46] Fix double reset in aic7xxx driver

[Joe Korty <joe.korty@ccur.com>]

Fix occasional PCI bus parity errors on the Dell PowerEdge 4600 during
boot.

Symptoms: The LCD display would turn orange and display "PCI SYSTEM
E13F5", and the following message would appear in /var/log/dmesg:
"Uhhuh. NMI received. Dazed and confused, but trying to continue".

By inserting a PCI card with a PDC20268 IDE controller and attaching to
that a Sony DRU-510A DVD RW burner with an unloaded tray, the failure
can be made to happen on every boot.

Cause: The aic7xxx driver was resetting the onboard AIC7891 SCSI controller
while waiting for a previous reset to complete.  This second reset confuses
the controller causing it to put bad data onto the PCI bus.

This is a backport of a RedHat 2.4.21-15.ELsmp fix.  A letter discussing
this problem, or one very close to it, may be found at:

   http://lists.us.dell.com/pipermail/linux-poweredge/2003-May/025010.html

Against 2.6.7 and 2.4.26.

Regards,
Joe


diff -ura base/drivers/scsi/aic7xxx/aic79xx_pci.c new/drivers/scsi/aic7xxx/aic79xx_pci.c
--- base/drivers/scsi/aic7xxx/aic79xx_pci.c	2004-06-16 01:19:22.000000000 -0400
+++ new/drivers/scsi/aic7xxx/aic79xx_pci.c	2004-07-12 12:50:11.000000000 -0400
@@ -452,8 +452,10 @@
 	 * or read prefetching could be initiated by the
 	 * CPU or host bridge.  Our device does not support
 	 * either, so look for data corruption and/or flaged
-	 * PCI errors.
+	 * PCI errors.  First pause without causing another
+	 * chip reset.
 	 */
+	hcntrl &= ~CHIPRST;
 	ahd_outb(ahd, HCNTRL, hcntrl|PAUSE);
 	while (ahd_is_paused(ahd) == 0)
 		;
diff -ura base/drivers/scsi/aic7xxx/aic7xxx_pci.c new/drivers/scsi/aic7xxx/aic7xxx_pci.c
--- base/drivers/scsi/aic7xxx/aic7xxx_pci.c	2004-06-16 01:18:57.000000000 -0400
+++ new/drivers/scsi/aic7xxx/aic7xxx_pci.c	2004-07-12 12:50:11.000000000 -0400
@@ -1284,8 +1284,10 @@
 	 * or read prefetching could be initiated by the
 	 * CPU or host bridge.  Our device does not support
 	 * either, so look for data corruption and/or flagged
-	 * PCI errors.
+	 * PCI errors.  First pause without causing another
+	 * chip reset.
 	 */
+	hcntrl &= ~CHIPRST;
 	ahc_outb(ahc, HCNTRL, hcntrl|PAUSE);
 	while (ahc_is_paused(ahc) == 0)
 		;