Message-ID: <27b8f3f2-a295-6960-2df5-3ee5e457fea3@gmail.com>
Date:   Fri, 22 Jan 2021 09:56:47 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     George McCollister <george.mccollister@...il.com>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Murali Karicheri <m-karicheri2@...com>, netdev@...r.kernel.org
Subject: Re: [RFC PATCH net-next 2/3] net: hsr: add DSA offloading support



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.

[snip]

>  
> +static inline bool netif_is_hsr_master(const struct net_device *dev)
> +{
> +	return dev->flags & IFF_MASTER && dev->priv_flags & IFF_HSR;
> +}
> +
> +static inline bool netif_is_hsr_slave(const struct net_device *dev)
> +{
> +	return dev->flags & IFF_SLAVE && dev->priv_flags & IFF_HSR;
> +}

I believe the kernel community is now trying to eliminate the use of the
terms master and slave, can you replace these with some HSR specific
naming maybe?
-- 
Florian

Powered by blists - more mailing lists