Messages in this thread | | | Date | Sun, 3 May 2009 00:26:05 -0400 | Subject | Re: Porting the ibm_newemac driver to use phylib (and other PHY/MAC questions) | From | Kyle Moffett <> |
| |
On Thu, Apr 30, 2009 at 6:21 PM, Kyle Moffett <kyle@moffetthome.net> wrote: >>> I'm also curious about the intent of the "mdio_instance" pointer (IE: >>> the "mdio-device" property). Is that used when all the PHY devices >>> are attached to the MDIO bus of only one of the (multiple) emac >>> devices? >> >> It's common especially on older SoCs using EMAC to have only one of >> the EMAC instance with an MDIO bus for configuring the PHYs. This is one >> of the reasons why I have the mutex in the low level MDIO access >> routines since 2 EMACs can try to talk to the same MDIO, and this is the >> problem I had with phylib back then which was doing everything in atomic >> contexts. > > Ok, good, the current mdiobus code seems to make handling this a good > deal easier.
Ok, I've dug through the docs on the 460EPx (the CPU I'm using), and I'd like some confirmation of the following:
* The EMAC hardware itself internally has its own dedicated MDIO/MDClk lines, driven by the STACR register.
* On many/most cpus, there is only a single set of external MDIO/MDClk pins, driven either off the ZMII bridge or the RGMII bridge.
* Both bridge-types have their own internal register for switching the external MDIO/MDClk pins between the two sets of internal EMAC<=>bridge links.
* Some SoCs have both an ZMII and an RGMII bridge, and the external MDIO/MDClk pins are only connected to one of the two bridges (How do I know which one? Alternatively, do I just program both and hope for the best?).
* Some older SoCs simply export the MDIO/MDClk pins from one of their internal EMAC chips and don't bother with running it through the multiplexing bridge.
Are there any SoCs which actually export the MDIO/MDClk pins from both/all of their EMACs?
Cheers, Kyle Moffett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |