Messages in this thread Patch in this message | | | Date | Wed, 15 Jun 2011 12:17:47 -0700 | From | Nishanth Aravamudan <> | Subject | libata/ipr/powerpc: regression between 2.6.39-rc4 and 2.6.39-rc5 |
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Hi Jeff,
It appears that commit 7b3a24c57d2eeda8dba9c205342b12689c4679f9 broke CD-ROMs on the IPR SATA bus on powerpc 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 commit in question is tagged as AHCI, but does touch the libata core. I'm not well-versed with this code, but here's what I think I know :)
From __scsi_add_device, we first allocate the target:
scsi_alloc_target -> shost->hostt->target_alloc -> ipr_target_alloc -> ata_port_alloc -> sets FROZEN
We error out when we allocate the sdev:
scsi_alloc_sdev -> shost->hostt->slave_alloc -> ipr_slave_alloc -> ipr_ata_slave_alloc -> ata_sas_port_init -> ata_port_probe
From what I can tell, the only place that explicitly clears the FROZEN flag is the error-handling code via ata_eh_thaw_port().
So I thought either we're not invoking the error-handler at probe time correctly to kick the port or perhaps the SAS code is not clearing the flag?
I tried the following patch:
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index d51f979..abd0e0b 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -3797,6 +3797,7 @@ EXPORT_SYMBOL_GPL(ata_sas_port_alloc); */ int ata_sas_port_start(struct ata_port *ap) { + ap->pflags &= ~ATA_PFLAG_FROZEN; return 0; } EXPORT_SYMBOL_GPL(ata_sas_port_start); and the CD-ROM drive works, but I have no idea if it's the right thing to do. I chose this particular change, FWIW, because we call ata_sas_port_start before we probe in ata_sas_port_init and it seems like we need to mark the port as not frozen before we init it? Perhaps that should really be a call to a thaw function, not sure. Let's just say the ATA/SAS/SCSI interactions are a bit hard to follow at first :)
Any insight you can provide would be great!
Thanks, Nish
-- Nishanth Aravamudan <nacc@us.ibm.com> IBM Linux Technology Center
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