External port Multiplier Support in linux

External port Multiplier Support in linux

[pinchu]

Hi Jeff,

We have an external RAID Disk Array which is having a port multiplier 
and four HDD behind the port multiplier. The RAID box is connected to 
host via SATA interface. The port multiplier we are using is implemented 
in FPGA. The linux kernel 2.6.28 is not detecting the port multiplier 
and devices behind it.

By any chance linux kernel 2.6.28 supports external port multiplier?
Does linux automatically detect port multiplier during bootup?
Di i need to write driver for detecting the port multiplier?

Thanks in advance.

Regards,
Pinchu

Re: External port Multiplier Support in linux

[Grant Grundler]

On Fri, Jul 10, 2009 at 6:36 AM, pinchu<pinchu4u@gmail.com> wrote:
> Hi Jeff,
>
> We have an external RAID Disk Array which is having a port multiplier and
> four HDD behind the port multiplier. The RAID box is connected to host via
> SATA interface. The port multiplier we are using is implemented in FPGA. The
> linux kernel 2.6.28 is not detecting the port multiplier and devices behind
> it.
>
> By any chance linux kernel 2.6.28 supports external port multiplier?

Yes.

> Does linux automatically detect port multiplier during bootup?

Yes.

> Di i need to write driver for detecting the port multiplier?

Yes. The SATA controller driver has to include support for port multipliers.

Here is how to determine if the SATA controller driver can support PMP:
grundler <2050>fgrep ATA_FLAG_PMP drivers/ata/*c
drivers/ata/ahci.c:             pi.flags |= ATA_FLAG_PMP;
drivers/ata/libata-core.c:      WARN_ON(ap->flags & ATA_FLAG_PMP);
drivers/ata/sata_fsl.c:                         ATA_FLAG_PMP | ATA_FLAG_NCQ),
drivers/ata/sata_mv.c:                            ATA_FLAG_PMP |
ATA_FLAG_ACPI_SATA,
drivers/ata/sata_sil24.c:                                 ATA_FLAG_AN
| ATA_FLAG_PMP,

So right now, it seems only 4 drivers can.

hth,
grant