libata/sas: only set FROZEN flag if new EH is supported

On 16.06.2011 [08:28:39 -0500], Brian King wrote:
> On 06/16/2011 02:51 AM, Tejun Heo wrote:
> > On Wed, Jun 15, 2011 at 04:34:17PM -0700, Nishanth Aravamudan wrote:
> >>> That looks like the right thing to do. For ipr's usage of
> >>> libata, we don't have the concept of a port frozen state, so this flag
> >>> should really never get set. The alternate way to fix this would be to
> >>> only set ATA_PFLAG_FROZEN in ata_port_alloc if ap->ops->error_handler
> >>> is not NULL.
> >>
> >> It seemed like ipr is as you say, but I wasn't sure if it was
> >> appropriate to make the change above in the common libata-scis code or
> >> not. I don't want to break some other device on accident.
> >>
> >> Also, I tried your suggestion, but I don't think that can happen in
> >> ata_port_alloc? ata_port_alloc is allocated ap itself, and it seems like
> >> ap->ops typically gets set only after ata_port_alloc returns?
> >
> > Maybe we can test error_handler in ata_sas_port_start()?
>
> Good point. Since libsas is converted to the new eh now, we would need to have
> this test.

Commit 7b3a24c5 ("ahci: don't enable
port irq before handler is registered") caused a regression for CD-ROMs
attached to the IPR SATA bus on Power machines:

  ata_port_alloc: ENTER
  ata_port_probe: ata1: bus probe begin
  ata1.00: ata_dev_read_id: ENTER
  ata1.00: failed to IDENTIFY (I/O error, err_mask=0x40)
  ata1.00: ata_dev_read_id: ENTER
  ata1.00: failed to IDENTIFY (I/O error, err_mask=0x40)
  ata1.00: limiting speed to UDMA7:PIO5
  ata1.00: ata_dev_read_id: ENTER
  ata1.00: failed to IDENTIFY (I/O error, err_mask=0x40)
  ata1.00: disabled
  ata_port_probe: ata1: bus probe end
  scsi_alloc_sdev: Allocation failure during SCSI scanning, some SCSI devices might not be configured

The FROZEN flag added in that commit is only cleared by the new EH code,
which is not used by ipr. Clear this flag in the SAS code if we don't
support new EH.
Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

drivers/ata/libata-scsi.c

@@ -3797,6 +3797,12 @@ EXPORT_SYMBOL_GPL(ata_sas_port_alloc);
  */
 int ata_sas_port_start(struct ata_port *ap)
 {
+	/*
+	 * the port is marked as frozen at allocation time, but if we don't
+	 * have new eh, we won't thaw it
+	 */
+	if (!ap->ops->error_handler)
+		ap->pflags &= ~ATA_PFLAG_FROZEN;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ata_sas_port_start);