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    SubjectRe: [PATCH RFC] Update documentation for KSZ DSA drivers so that new drivers can be added
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    On 09/08/2017 12:48 PM, Tristram.Ha@microchip.com wrote:
    >> -----Original Message-----
    >> From: Maxim Uvarov [mailto:muvarov@gmail.com]
    >> Sent: Friday, September 08, 2017 12:00 PM
    >> To: Florian Fainelli
    >> Cc: Tristram Ha - C24268; Andrew Lunn; Pavel Machek; Nathan Conrad; Vivien
    >> Didelot; netdev; linux-kernel@vger.kernel.org; Woojung Huh - C21699
    >> Subject: Re: [PATCH RFC] Update documentation for KSZ DSA drivers so that new
    >> drivers can be added
    >>
    >> 2017-09-08 21:48 GMT+03:00 Florian Fainelli <f.fainelli@gmail.com>:
    >>> On 09/07/2017 02:11 PM, Tristram.Ha@microchip.com wrote:
    >>>> From: Tristram Ha <Tristram.Ha@microchip.com>
    >>>>
    >>>> Add other KSZ switches support so that patch check does not complain.
    >>>>
    >>>> Signed-off-by: Tristram Ha <Tristram.Ha@microchip.com>
    >>>> ---
    >>>> Documentation/devicetree/bindings/net/dsa/ksz.txt | 117
    >>>> ++++++++++++----------
    >>>> 1 file changed, 62 insertions(+), 55 deletions(-)
    >>>>
    >>>> diff --git a/Documentation/devicetree/bindings/net/dsa/ksz.txt
    >>>> b/Documentation/devicetree/bindings/net/dsa/ksz.txt
    >>>> index 0ab8b39..34af0e0 100644
    >>>> --- a/Documentation/devicetree/bindings/net/dsa/ksz.txt
    >>>> +++ b/Documentation/devicetree/bindings/net/dsa/ksz.txt
    >>>> @@ -3,8 +3,15 @@ Microchip KSZ Series Ethernet switches
    >>>>
    >>>> Required properties:
    >>>>
    >>>> -- compatible: For external switch chips, compatible string must be
    >>>> exactly one
    >>>> - of: "microchip,ksz9477"
    >>>> +- compatible: Should be "microchip,ksz9477" for KSZ9477 chip,
    >>>> + "microchip,ksz8795" for KSZ8795 chip,
    >>>> + "microchip,ksz8794" for KSZ8794 chip,
    >>>> + "microchip,ksz8765" for KSZ8765 chip,
    >>>> + "microchip,ksz8895" for KSZ8895 chip,
    >>>> + "microchip,ksz8864" for KSZ8864 chip,
    >>>> + "microchip,ksz8873" for KSZ8873 chip,
    >>>> + "microchip,ksz8863" for KSZ8863 chip,
    >>>> + "microchip,ksz8463" for KSZ8463 chip
    >>>
    >>
    >>
    >> Tristram, does any of this devices support chaining?
    >>
    >> Maxim.
    >
    > They do not if you mean daisy-chaining the switches together.

    Marvell tags allow you to specify both a port and switch index
    destination after setting up an appropriate routing table, I am assuming
    this is not supported.

    What happens though if I connect two KSZ switches ones to another say:

    eth0
    -> KSZ8463
    -> KSZ8463

    Will the first switch terminates KSZ tag if it sees two tags
    encapsulated in another, something like this:

    | MAC DA | MAC SA | .... payload | Inner KSZ tag | Inner KSZ tag | FCS |

    >
    > There is always a problem that once tail tagging mode is enabled
    > sending a frame through the MAC without going through the DSA
    > layer will cause the frame to be dropped.

    Yes, once the master network device is used for DSA, it is still usable
    directly by e.g: applications, but it won't do anything if the switch is
    configured such that it drops ingressing frames not having the proper
    tag. We documented that here:

    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/networking/dsa/dsa.txt#n275
    --
    Florian

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