On 20.08.2019 15:36, Christian Herber wrote: > On 19.08.2019 21:07, Heiner Kallweit wrote: >> Caution: EXT Email >> >> On 19.08.2019 08:32, Christian Herber wrote: >>> On 16.08.2019 22:59, Heiner Kallweit wrote: >>>> On 15.08.2019 17:32, Christian Herber wrote: >>>>> This patch adds basic support for BASE-T1 PHYs in the framework. >>>>> BASE-T1 PHYs main area of application are automotive and industrial. >>>>> BASE-T1 is standardized in IEEE 802.3, namely >>>>> - IEEE 802.3bw: 100BASE-T1 >>>>> - IEEE 802.3bp 1000BASE-T1 >>>>> - IEEE 802.3cg: 10BASE-T1L and 10BASE-T1S >>>>> >>>>> There are no products which contain BASE-T1 and consumer type PHYs like >>>>> 1000BASE-T. However, devices exist which combine 100BASE-T1 and >>>>> 1000BASE-T1 >>>>> PHYs with auto-negotiation. >>>> >>>> Is this meant in a way that *currently* there are no PHY's combining >>>> Base-T1 >>>> with normal Base-T modes? Or are there reasons why this isn't possible in >>>> general? I'm asking because we have PHY's combining copper and fiber, and >>>> e.g. >>>> the mentioned Aquantia PHY that combines NBase-T with 1000Base-T2. >>>> >>>>> >>>>> The intention of this patch is to make use of the existing Clause 45 >>>>> functions. >>>>> BASE-T1 adds some additional registers e.g. for aneg control, which >>>>> follow a >>>>> similiar register layout as the existing devices. The bits which are used >>>>> in >>>>> BASE-T1 specific registers are the same as in basic registers, thus the >>>>> existing functions can be resued, with get_aneg_ctrl() selecting the >>>>> correct >>>>> register address. >>>>> >>>> If Base-T1 can't be combined with other modes then at a first glance I see >>>> no >>>> benefit in defining new registers e.g. for aneg control, and the standard >>>> ones >>>> are unused. Why not using the standard registers? Can you shed some light >>>> on that? >>>> >>>> Are the new registers internally shadowed to the standard location? >>>> That's something I've seen on other PHY's: one register appears in >>>> different >>>> places in different devices. >>>> >>>>> The current version of ethtool has been prepared for 100/1000BASE-T1 and >>>>> works >>>>> with this patch. 10BASE-T1 needs to be added to ethtool. >>>>> >>>>> Christian Herber (1): >>>>> Added BASE-T1 PHY support to PHY Subsystem >>>>> >>>>> drivers/net/phy/phy-c45.c | 113 +++++++++++++++++++++++++++++++---- >>>>> drivers/net/phy/phy-core.c | 4 +- >>>>> include/uapi/linux/ethtool.h | 2 + >>>>> include/uapi/linux/mdio.h | 21 +++++++ >>>>> 4 files changed, 129 insertions(+), 11 deletions(-) >>>>> >>>> >>>> Heiner >>>> >>> >>> Hi Heiner, >>> >>> I do not think the Aquantia part you are describing is publicly >>> documented, so i cannot comment on that part. >> Right, datasheet isn't publicly available. All I wanted to say with >> mentioning this PHY: It's not a rare exception that a PHY combines >> standard BaseT modes with "non-consumer" modes for special purposes. >> One practical use case of this proprietary 1000Base-T2 mode is >> re-using existing 2-pair cabling in aircrafts. >> >>> There are multiple reasons why e.g. xBASE-T1 plus 1000BASE-T is >>> unlikely. First, the is no use-case known to me, where this would be >>> required. Second, there is no way that you can do an auto-negotiation >>> between the two, as these both have their own auto-neg defined (Clause >>> 28/73 vs. Clause 98). Thirdly, if you would ever have a product with >>> both, I believe it would just include two full PHYs and a way to select >>> which flavor you want. Of course, this is the theory until proven >>> otherwise, but to me it is sufficient to use a single driver. >>> >> I'm with you if you say it's unlikely. However your statement in the >> commit message leaves the impression that there can't be such a device. >> And that's a difference. >> >> Regarding "including two full PHYs": >> This case we have already, there are PHYs combining different IP blocks, >> each one supporting a specific mode (e.g. copper and fiber). There you >> also have the case of different autoneg methods, clause 28 vs. clause 37. >> >>> The registers are different in the fields they include. It is just that >>> the flags which are used by the Linux driver, like restarting auto-neg, >>> are at the same position. >>> >> Good to know. Your commit description doesn't mention any specific PHY. >> I suppose you have PHYs you'd like to operate with the genphy_c45 driver. >> Could you give an example? And ideally, is a public datasheet available? >> >>> Christian >>> >>> >> Heiner >> > > There are no public BASE-T1 devices on the market right now that use > Clause 45 standard registers. The first such products were developed > before the IEEE standard (BroadR-Reach) and used Clause 22 access (see > e.g. the support in the Kernel for TJA110x). > > The most convenient way to test with a BASE-T1 device would be to use an > SFP (e.g. > https://technica-engineering.de/produkt/1000base-t1-sfp-module/). > Alternative source could be Goepel. > > There are also a number of media-converters around where one could break > out the MDIO and connect to a processor. Of course, in all cases it > should be made sure that this is a Clause-45 device. > > As all relevant parts are NDA-restricted, this is pretty much all the > information I can share. > If no such device is on the market yet, then I'd suggest: - wait for such a device to see whether genphy_c45 driver is really sufficient or whether other chip features require a dedicated driver anyway. In the latter case it may be better to add dedicated T1 functions to phylib. - add the missing 10BASE-T1L and 10BASE-T1S support meanwhile
The current patch set IMO is a little bit hacky. I'm not 100% happy with the implicit assumption that there can't be devices supporting T1 and classic BaseT modes or fiber modes. Andrew: Do you have an opinion on that? > Christian > > Heiner
