On Wed, 2012/11/28, Robert Hancock wrote:
> On 11/23/2012 07:01 PM, Norman Diamond wrote:
>> I wrot on October 17, 2012 2:25 PM
>>
>>> I'm trying to use an SIL3726 with 5 SATA drives and an SIL3132.
>>> FBS should work, right? But performance looks like CBS.
>>> Is there some way to check if FBS is actually enabled?
>>
>> I added some ata_dev_printk calls in file libahci.c,
>> static void ahci_enable_fbs(struct ata_port *ap)
>> and a few other places, but none of them were logged.
>> In file libata-pmp.c, the following continues to be logged:
>> if (print_info) {
>> ata_dev_printk(dev, KERN_INFO, "Port Multiplier %s, "
>> "0x%04x:0x%04x r%d, %d ports, feat 0x%x/0x%x\n",
>> sata_pmp_spec_rev_str(gscr), vendor, devid,
>> sata_pmp_gscr_rev(gscr),
>> nr_ports, gscr[SATA_PMP_GSCR_FEAT_EN],
>> gscr[SATA_PMP_GSCR_FEAT]);
>> ata3.15: Port Multiplier 1.1, 0x1095:0x3726 r23, 6 ports, feat 0x1/0x9
>>
>> Finally I figured out that the sil24 driver uses its own port multiplier
>> code and never calls the libahci code.
>>
>> So the reason why it performs like CBS instead of FBS is due to
>> something in the sil24 driver, or the SIL3132 HBA firmware, or the
>> SIL3726 port multiplier firmware. I still can't figure out which.
>
> sata_sil24 doesn't support FBS. The datasheet seems to have some mention
> of FBS support in the chip, but I don't know if that's actually the case.
OK. Although we can't figure out the underlying reason, it is clear that the combination of SIL3132 (or SIL3124) HBA and Linux will not support FBS regardless of SIL3726's capability. Everywhere I looked, there were statements that SIL3132, SIL3124, and SIL3726 support FBS, but if the vendor doesn't release details of the HBAs then obviously it's hard to get FBS working. Sometimes it's amazing that Linux volunteers can make a chip work at all.
Thank you for the information. At least now I know not to waste more days trying to figure out where to add more printk's and still not accomplishing anything.
After posting the question, I tried a Marvell SAS HBA but having trouble that might be due to a SAS-to-eSATA cable maybe being the wrong variety. It sure is frustrating trying to find a way to get FBS to work.
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