netdev - RE: [PATCH RFC 0/6] DPAA2 MAC Driver

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Message-ID: <VI1PR0402MB2800BBC003EA7C572FBEF09DE0EE0@VI1PR0402MB2800.eurprd04.prod.outlook.com>
Date:   Fri, 14 Jun 2019 15:26:50 +0000
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
CC:     "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Alexandru Marginean <alexandru.marginean@....com>,
        Ioana Ciocoi Radulescu <ruxandra.radulescu@....com>
Subject: RE: [PATCH RFC 0/6] DPAA2 MAC Driver

> Subject: Re: [PATCH RFC 0/6] DPAA2 MAC Driver
> 
> On Fri, Jun 14, 2019 at 02:55:47AM +0300, Ioana Ciornei wrote:
> > After today's discussion with Russell King about what phylink exposes
> > in
> > .mac_config(): https://marc.info/?l=linux-netdev&m=156043794316709&w=2
> > I am submitting for initial review the dpaa2-mac driver model.
> >
> > At the moment, pause frame support is missing so inherently all the
> > USXGMII modes that rely on backpressure applied by the PHY in rate
> > adaptation between network side and system side don't work properly.
> >
> > As next steps, the driver will have to be integrated with the SFP bus
> > so commands such as 'ethtool --dump-module-eeprom' will have to work
> > through the current callpath through firmware.
> 
> From what I understand having read the doc patch, would it be fair to say
> that every operation that is related to the link state has to be passed from
> the ETH driver to the firmware, and then from the firmware back to the
> kernel to the MAC driver?

That is correct.

> 
> Does this mean that "ethtool --dump-module-eeprom" goes through this
> process as well - eth driver into firmware, which then gets forwarded out of
> the formware on the MAC side, via phylink to the SFP cage?
> 
> If that is true, what is the proposal - to forward a copy of the EEPROM on
> module insertion into the firmware, so that it is stored there when anyone
> requests it?  What about the diagnostic monitoring that is real-time?
> 

At the moment, we do not have a proposal that could solve all these issues.
We thought about a solution where the eth driver issues a command to the firmware that then issues an IRQ to the mac driver which could retrieve and then pass back the information.
This doesn't seem too feasible since the ethernet driver should be waiting for the data to arrive back from the firmware while in an ethtool callback.


> Or is the SFP cage entirely handled by firmware?

No, the SFP cage is not handled by firmware.

> 
> > This poses somewhat of a problem, as
> > dpaa2-eth lacks any handle to the phy so it will probably need further
> > modification to the API that the firmware exposes (same applies to
> > 'ethtool --phy-statistics').
> 
> This again sounds like the eth driver forwards the request to firmware which
> then forwards it to the mac driver for it to process.
> 
> Is that correct?

Correct.

> 
> >
> > The documentation patch provides a more complete view of the software
> > architecture and the current implementation.
> >
> > Ioana Ciornei (4):
> >   net: phy: update the autoneg state in phylink_phy_change
> >   dpaa2-mac: add MC API for the DPMAC object
> >   dpaa2-mac: add initial driver
> >   net: documentation: add MAC/PHY proxy driver documentation
> >
> > Ioana Radulescu (2):
> >   dpaa2-eth: add support for new link state APIs
> >   dpaa2-eth: add autoneg support
> >
> >  .../freescale/dpaa2/dpmac-driver.rst               | 159 ++++++
> >  .../device_drivers/freescale/dpaa2/index.rst       |   1 +
> >  MAINTAINERS                                        |   8 +
> >  drivers/net/ethernet/freescale/dpaa2/Kconfig       |  13 +
> >  drivers/net/ethernet/freescale/dpaa2/Makefile      |   2 +
> >  .../net/ethernet/freescale/dpaa2/dpaa2-ethtool.c   |  83 +++-
> >  drivers/net/ethernet/freescale/dpaa2/dpaa2-mac.c   | 541
> +++++++++++++++++++++
> >  drivers/net/ethernet/freescale/dpaa2/dpmac-cmd.h   | 107 ++++
> >  drivers/net/ethernet/freescale/dpaa2/dpmac.c       | 369
> ++++++++++++++
> >  drivers/net/ethernet/freescale/dpaa2/dpmac.h       | 210 ++++++++
> >  drivers/net/ethernet/freescale/dpaa2/dpni-cmd.h    |  35 ++
> >  drivers/net/ethernet/freescale/dpaa2/dpni.c        |  70 +++
> >  drivers/net/ethernet/freescale/dpaa2/dpni.h        |  27 +
> >  drivers/net/phy/phylink.c                          |   1 +
> >  14 files changed, 1612 insertions(+), 14 deletions(-)  create mode
> > 100644
> > Documentation/networking/device_drivers/freescale/dpaa2/dpmac-
> driver.r
> > st  create mode 100644
> > drivers/net/ethernet/freescale/dpaa2/dpaa2-mac.c
> >  create mode 100644 drivers/net/ethernet/freescale/dpaa2/dpmac-cmd.h
> >  create mode 100644 drivers/net/ethernet/freescale/dpaa2/dpmac.c
> >  create mode 100644 drivers/net/ethernet/freescale/dpaa2/dpmac.h
> >
> > --
> > 1.9.1
> >