ide: Linux reports drive diagnostic failures on boot

[Mark Cave-Ayland]

During my latest OpenBIOS boot tests I've noticed the following IDE diagnostics 
failure message appearing in dmesg at Linux boot time when booting from CDROM on both 
SPARC64 and PPC:

[    9.347342] scsi host0: pata_cmd64x
[    9.369055] scsi host1: pata_cmd64x
[    9.371622] ata1: PATA max UDMA/33 cmd 0x1fe02008000 ctl 0x1fe02008080 bmdma 
0x1fe02008200 irq 8
[    9.372805] ata2: PATA max UDMA/33 cmd 0x1fe02008100 ctl 0x1fe02008180 bmdma 
0x1fe02008208 irq 8
[    9.711740] ata2.00: ATAPI: QEMU DVD-ROM, 2.5+, max UDMA/100
[    9.712591] ata2.00: Drive reports diagnostics failure. This may indicate a 
drive
[    9.713256] ata2.00: fault or invalid emulation. Contact drive vendor for 
information.
[    9.737677] ata2.00: configured for UDMA/33
[    9.790179] scsi 1:0:0:0: CD-ROM            QEMU     QEMU DVD-ROM     2.5+ PQ: 0 
ANSI: 5
[   10.381172] hme 0000:01:01.1 enp1s1f1: renamed from eth0
[   10.508819] sr 1:0:0:0: [sr0] scsi3-mmc drive: 4x/4x cd/rw xa/form2 tray
[   10.509805] cdrom: Uniform CD-ROM driver Revision: 3.20


A session with git bisect points to the following commit:

55adb3c45620c31f29978f209e2a44a08d34e2da is the first bad commit
commit 55adb3c45620c31f29978f209e2a44a08d34e2da
Author: John Snow <jsnow@redhat.com>
Date:   Fri Jul 24 01:23:00 2020 -0400

    ide: cancel pending callbacks on SRST

    The SRST implementation did not keep up with the rest of IDE; it is
    possible to perform a weak reset on an IDE device to remove the BSY/DRQ
    bits, and then issue writes to the control/device registers which can
    cause chaos with the state machine.

    Fix that by actually performing a real reset.

    Reported-by: Alexander Bulekov <alxndr@bu.edu>
    Fixes: https://bugs.launchpad.net/qemu/+bug/1878253
    Fixes: https://bugs.launchpad.net/qemu/+bug/1887303
    Fixes: https://bugs.launchpad.net/qemu/+bug/1887309
    Signed-off-by: John Snow <jsnow@redhat.com>

:040000 040000 70a7c1cfbafb22fa815d3ae4d7ed075ac3918188 
3f37762f20e9ca9d2874eaf819d7175a1dca1dd9 M      hw


John/Alexander: any chance you could take a look at this? The message above is really 
simple to reproduce under qemu-system-sparc64 using 
http://cdimage.debian.org/cdimage/ports/9.0/sparc64/iso-cd/debian-9.0-sparc64-NETINST-1.iso 
and the following command line:

./qemu-system-sparc64 \
    -cdrom debian-9.0-sparc64-NETINST-1.iso \
    -m 256 \
    -nographic \
    -boot d


ATB,

Mark.