netdev - Re: [RFC PATCH net-next 2/3] net: hsr: add DSA offloading support

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Date:   Fri, 22 Jan 2021 10:00:07 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     George McCollister <george.mccollister@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "grygorii.strashko@...com" <grygorii.strashko@...com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Nishanth Menon <nm@...com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Jonathan Corbet <corbet@....net>, netdev@...r.kernel.org
Subject: Re: [RFC PATCH net-next 2/3] net: hsr: add DSA offloading support



On 1/22/2021 9:56 AM, Florian Fainelli wrote:
> 
> 
> On 1/22/2021 7:59 AM, George McCollister wrote:
>> Add support for offloading of HSR/PRP (IEC 62439-3) tag insertion
>> tag removal, duplicate generation and forwarding on DSA switches.
>>
>> Use a new netdev_priv_flag IFF_HSR to indicate that a device is an HSR
>> device so DSA can tell them apart from other devices in
>> dsa_slave_changeupper.
>>
>> Add DSA_NOTIFIER_HSR_JOIN and DSA_NOTIFIER_HSR_LEAVE which trigger calls
>> to .port_hsr_join and .port_hsr_leave in the DSA driver for the switch.
>>
>> The DSA switch driver should then set netdev feature flags for the
>> HSR/PRP operation that it offloads.
>>     NETIF_F_HW_HSR_TAG_INS
>>     NETIF_F_HW_HSR_TAG_RM
>>     NETIF_F_HW_HSR_FWD
>>     NETIF_F_HW_HSR_DUP
>>
>> For HSR, insertion involves the switch adding a 6 byte HSR header after
>> the 14 byte Ethernet header. For PRP it adds a 6 byte trailer.
>>
>> Tag removal involves automatically stripping the HSR/PRP header/trailer
>> in the switch. This is possible when the switch also preforms auto
>> deduplication using the HSR/PRP header/trailer (making it no longer
>> required).
>>
>> Forwarding involves automatically forwarding between redundant ports in
>> an HSR. This is crucial because delay is accumulated as a frame passes
>> through each node in the ring.
>>
>> Duplication involves the switch automatically sending a single frame
>> from the CPU port to both redundant ports. This is required because the
>> inserted HSR/PRP header/trailer must contain the same sequence number
>> on the frames sent out both redundant ports.
>>
>> Signed-off-by: George McCollister <george.mccollister@...il.com>
> 
> This is just a high level overview for now, but I would split this into two:
> 
> - a patch that adds HSR offload to the existing HSR stack and introduces
> the new netdev_features_t bits to support HSR offload, more on that below
> 
> - a patch that does the plumbing between HSR and within the DSA framework
> 
>> ---
>>  Documentation/networking/netdev-features.rst | 20 ++++++++++++++++
>>  include/linux/if_hsr.h                       | 22 ++++++++++++++++++
>>  include/linux/netdev_features.h              |  9 ++++++++
>>  include/linux/netdevice.h                    | 13 +++++++++++
>>  include/net/dsa.h                            | 13 +++++++++++
>>  net/dsa/dsa_priv.h                           | 11 +++++++++
>>  net/dsa/port.c                               | 34 ++++++++++++++++++++++++++++
>>  net/dsa/slave.c                              | 13 +++++++++++
>>  net/dsa/switch.c                             | 24 ++++++++++++++++++++
>>  net/ethtool/common.c                         |  4 ++++
>>  net/hsr/hsr_device.c                         | 12 +++-------
>>  net/hsr/hsr_forward.c                        | 27 +++++++++++++++++++---
>>  net/hsr/hsr_forward.h                        |  1 +
>>  net/hsr/hsr_main.c                           | 14 ++++++++++++
>>  net/hsr/hsr_main.h                           |  8 +------
>>  net/hsr/hsr_slave.c                          | 13 +++++++----
>>  16 files changed, 215 insertions(+), 23 deletions(-)
>>  create mode 100644 include/linux/if_hsr.h
>>
>> diff --git a/Documentation/networking/netdev-features.rst b/Documentation/networking/netdev-features.rst
>> index a2d7d7160e39..4eab45405031 100644
>> --- a/Documentation/networking/netdev-features.rst
>> +++ b/Documentation/networking/netdev-features.rst
>> @@ -182,3 +182,23 @@ stricter than Hardware LRO.  A packet stream merged by Hardware GRO must
>>  be re-segmentable by GSO or TSO back to the exact original packet stream.
>>  Hardware GRO is dependent on RXCSUM since every packet successfully merged
>>  by hardware must also have the checksum verified by hardware.
>> +
>> +* hsr-tag-ins-offload
>> +
>> +This should be set for devices which insert an HSR (highspeed ring) tag
>> +automatically when in HSR mode.
>> +
>> +* hsr-tag-rm-offload
>> +
>> +This should be set for devices which remove HSR (highspeed ring) tags
>> +automatically when in HSR mode.
>> +
>> +* hsr-fwd-offload
>> +
>> +This should be set for devices which forward HSR (highspeed ring) frames from
>> +one port to another in hardware.
>> +
>> +* hsr-dup-offload
>> +
>> +This should be set for devices which duplicate outgoing HSR (highspeed ring)
>> +frames in hardware.
> 
> Do you think we can start with a hsr-hw-offload feature and create new
> bits to described how challenged a device may be with HSR offload? Is it
>  reasonable assumption that functional hardware should be able to
> offload all of these functions or none of them?
> 
> It may be a good idea to know what the platform that Murali is working
> on or has worked on is capable of doing, too.

Murali's email address is bouncing, adding Grygorii, Kishon and
Nishanth, they may know.
-- 
Florian