ATAPI CD still not detected, verbose boot logs available

[Bruce Evans]

On Tue, 2 Dec 2003, Soren Schmidt wrote:

> It seems Christoph Sold wrote:
> > FreeBSD 5.2-B still does not detect my ATAPI DVD-ROM drive. This used t=
o
> > work until S=F8ren's ATAng commits. Other OSes (Win, Linux, Solaris)
> > detect the drive appropriately.
>
> Hmm from the bootlogs it seems that your drive does not set the proper
> ATAPI signature, thats why detection fails:
>
> atapci0: <VIA 82C686A UDMA66 controller> port 0xd800-0xd80f at device 4.1=
 on pci0
> ata0: reset tp1 mask=3D03 ostat0=3D50 ostat1=3D50
> ata0-master: stat=3D0x80 err=3D0x80 lsb=3D0x80 msb=3D0x80
               !!!!!!!!! bit 0x80 set says that the master is busy
> ata0-slave:  stat=3D0x00 err=3D0x01 lsb=3D0x14 msb=3D0x80
>                                          ^^^^^^^^ should be 0xeb
> ata0-master: stat=3D0x50 err=3D0x01 lsb=3D0x00 msb=3D0x00
               !!!!!!!!! now the master is unbusy
> ata0: reset tp2 mask=3D03 stat0=3D50 stat1=3D00 devices=3D0x1<ATA_MASTER>
> ata0: at 0x1f0 irq 14 on atapci0
> ata0: [MPSAFE]

Accessing the slave while the master is busy is invalid.  I believe the
failure mechanism is that the master keeps driving the bus while it is
busy, so reads of the slave registers give garbage.  This isn't a problem
unless the slave becomes ready first and it manages to write a success
code to the "err" register.  Then we trust the garbage.  It doesn't help
that the master eventually becomes ready, since we don't read the slave
registers again.

> There isn't much I can do about that one except you experimenting with
> the device and finding out why it fails setting the right signature....

Er, I sent patches for this a few months ago.  After reanalysing their
debugging putput combined with the above debugging output, I think
this bug is is the usual case if there are 2 drives and the drives'
timing after reset is as follows:

=09o The master must take more than 100 msec to become ready.
=09  Otherwise the 100 msec initial delay hides the bug.
=09o The slave must become ready before the master.  Otherwise
=09  there is no problem with using garbage slave registers,
=09  although accessing them is strictly invalid.

The bug is just not often seen since most drives don't take 100 msec to
become ready.  I only see it on a system with an 8-9 year old pre-ATA
IDE drive that takes 574 msec to become ready.

For a quick fix, try increasing the initial delay of 100 msec to a second
or more.

Bruce