[U-Boot] [PATCH] revert "tsec: Force TBI PHY to 1000Mbps fullduplex in SGMII mode"

Li Yang-R58472
2010-11-18T06:50:48Z

>Subject: RE: [U-Boot] [PATCH] revert "tsec: Force TBI PHY to 1000Mbps
>fullduplex in SGMII mode"
>
>On Wed, 2010-11-17 at 21:13 -0700, Li Yang-R58472 wrote:
>> >Subject: Re: [U-Boot] [PATCH] revert "tsec: Force TBI PHY to 1000Mbps
>> >full duplex in SGMII mode"
>> >
>> >Hi Zhao,
>> >
>> >> In message <1289986984-2314-1-git-send-email-b26998@freescale.com>
>> >> you
>> >wrote:
>> >> > On P2020DS and MPC8572DS, the link to SGMII card which use
>> >> > Vitesse
>> >> > VSC8234 PHY can't come up. Current TBI PHY
>> >> > settings(TBICR_SETTINGS) for SGMII mode cause link problems.
>> >> >
>> >> > Revert commit 46e91674fb4b6d06c6a4984c0b5ac7d9a16923f4, and fix it.
>> >
>> >Based on my company's discussions with Freescale and Freescale's
>> >appnotes I believe that the current implementation is correct. I
>> >make reference to some of this in the original patch:
>> >http://old.nabble.com/-U-Boot---PATCH--tsec:-Force-TBI-PHY-to-1000Mbp
>> >s- full-duplex-in-SGMII-mode-td26188785.html
>> >
>> >We use Broadcom PHYs on our boards, which likely has something to do
>> >with the discrepancies between the P2020DS/MPC8572DS vs the
>> >XPedite5370/XPedite5500. Unless you have additional information that
>> >shows that in-band SGMII auto-negotiation does work per the spec I'd
>> >prefer to keep the current tsec.c code and add
>> >CONFIG_TSEC_TBICR_SETTINGS workarounds to the P2020DS (already done
>> >in commit
>> >90b5bf211b85eee10c34cbeb907ce381142b7c99?) and MPC8572DS.
>>
>>
>> Hi Peter,
>>
>> From the App Note you mentioned, I didn't find that the auto-negotiation
>can't be used.
>
>My understanding is that the SGMII link is always at 1000Mbps speed - see
>figure 1 from the app note. Additionally look at figure 3. My understand
>from it, and the app note's text is that SGMII auto-negotiation doesn't
>really occur - its just passing the PHY-side auto-negotiation results to
>the Freescale MAC, which software then configures. I'm not sure what the
>purpose of the "SGMII auto-negotiation" is - its not really auto-
>negotiating and the same information can be read from the PHY via its MDIO
>interface, which is what is happening on X-ES boards currently.

I guess the point is to save MDIO signals to the external PHY and read the
negotiated result from the internal TBI PHY.

>
>We were told by a Freescale FAE that SGMII auto-negotiation wasn't
>supported, although 1000 BASE-X auto-negotation was (which mirrored our
>test results). I can dig up the old emails tomorrow at the office with
>the details.
>
>> Actually we need the auto-negotiation enabled for almost all Freescale
>reference boards such as P2020DS, MPC8572DS and P1/P2 RDB boards. If we
>disable the auto-negotiation on these boards, the SGMII link won't
>work. So I guess it might be more common to use auto-negotiation, and a
>fixed 1000M link is more like a special case. I'm not sure what's the
>recommended way for SGMII PHY interconnect though.
>
>And auto-negotation doesn't work on X-ES hardware which all use Broadcom
>PHYs - which is why I made the original change after consulting a
>Freescale FAE. Its not a huge deal to me either way as long as the
>XPedite5370 and XPedite5500 continue to not use SGMII auto-negotiation.
>Can someone at Freescale provide a definitive answer about what the proper
>SGMII auto-negotiation scheme is? And has anyone used it successfully or
>unsuccessfully with a non-Vitesse PHY?
>
>Best,
>Peter