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SubjectRe: port multiplier problem
Hi all,

Any suggestion?

Thanks,
Chandra

On 2/4/10 12:59 PM, Grant Grundler wrote:
> On Wed, Feb 3, 2010 at 7:24 PM, Tejun Heo<tj@kernel.org> wrote:
>
>> On 02/04/2010 11:37 AM, Grant Grundler wrote:
>>
>>> I had two questions on that thread that never got answered:
>>> http://markmail.org/message/snpekoj4qexrslk5
>>>
>>> | How can we find out if anyone has the SEMB properly wired up?
>>> | Would it be hard to make libata aware of "SEMB port not responding" case?
>>> | ie if the SEMB port times out or has no link, reduce the port count of
>>> | the sil3726 PMP by one.
>>> |
>>> | Maybe add a "enable_sil24_semb" flag to libata?
>>> | (avoid checking unless someone asks for it). I hate magic flags but also
>>> | don't want to subject most people to the timeout delay.
>>>
>>> I (or Gwendal) can post a patch (and lightly test) for any of the above.
>>> Just need to get some guidance so we don't waste our time.
>>>
>> It's not really sil24 tho. But anyways, I think we can just disable
>> them altogether. It's not like they have ever worked. Just limiting
>> both 3726 and 4726 to 5 ports should be fine.
>>
> Sorry - You are right. I meant "enable_sil3726_semb".
>
> I'm not sure we need to limit the SEMB ports anymore either. See below.
>
>
>> That said, I'm not
>> quite sure this is relevant to the reported problem but it's worth a
>> shot.
>>
> I didn't have a better idea.
>
> I'm seeing this in sata_pmp_quirks() since ATA_LFLAG_NO_SRST was introduced:
> 337 static void sata_pmp_quirks(struct ata_port *ap)
> 338 {
> 339 u32 *gscr = ap->link.device->gscr;
> 340 u16 vendor = sata_pmp_gscr_vendor(gscr);
> 341 u16 devid = sata_pmp_gscr_devid(gscr);
> 342 struct ata_link *link;
> 343
> 344 if (vendor == 0x1095&& devid == 0x3726) {
> 345 /* sil3726 quirks */
> 346 ata_for_each_link(link, ap, EDGE) {
> 347 /* Class code report is unreliable and SRST
> 348 * times out under certain configurations.
> 349 */
> 350 if (link->pmp< 5)
> 351 link->flags |= ATA_LFLAG_NO_SRST |
> 352 ATA_LFLAG_ASSUME_ATA;
> 353
> 354 /* port 5 is for SEMB device and it
> doesn't like SR ST */
> 355 if (link->pmp == 5)
> 356 link->flags |= ATA_LFLAG_NO_SRST |
> 357 ATA_LFLAG_ASSUME_SEMB;
> 358 }
>
>
> But the ATA_LFLAG_NO_SRST used in line 351 is not present in the
> 2.6.26 tree I know works with PMPs. The original commit comment isn't
> specific about exactly which HW had problems:
> http://www.mail-archive.com/git-commits-head@vger.kernel.org/msg24335.html
>
> "Some links on some PMPs locks up on SRST and/or report incorrect
> device signature. Implement ATA_LFLAG_NO_SRST, ASSUME_ATA and
> ASSUME_SEMB to handle these quirky links. NO_SRST makes EH avoid
> SRST. ASSUME_ATA and SEMB forces class code to ATA and SEMB_UNSUP
> respectively. Note that SEMB isn't currently supported yet so the
> _UNSUP variant is used."
>
>
> Can you publish which PMP implementations sometimes lock up on SRST?
>
> I doubt this is related to the problem Chandra is seeing but again,
> don't have better ideas.
>
> BTW, this same kernel works fine without disabling port 5 (SEMB port).
> I didn't know
> this until I just looked. I know previous source trees Google used
> ignored SEMB port
> on 3726 and I mistakenly assumed this one did too. :(
>
> thanks,
> grant
>
>



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