netdev - Re: [RFC 3/7] net: ethernet: mtk_eth_soc: implement flow offloading to WED devices

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Message-ID: <c6887708-6f75-bc05-1934-ddffa2f395a0@nbd.name>
Date:   Fri, 16 Jul 2021 08:09:36 +0200
From:   Felix Fietkau <nbd@....name>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        ryder.lee@...iatek.com
Subject: Re: [RFC 3/7] net: ethernet: mtk_eth_soc: implement flow offloading
 to WED devices


On 2021-07-15 23:36, Pablo Neira Ayuso wrote:
> On Wed, Jul 14, 2021 at 10:26:08AM +0200, Felix Fietkau wrote:
>> On 2021-07-13 20:56, Pablo Neira Ayuso wrote:
> [...]
>> >> --- a/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
>> >> +++ b/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
>> >> @@ -10,6 +10,7 @@
>> >>  #include <net/pkt_cls.h>
>> >>  #include <net/dsa.h>
>> >>  #include "mtk_eth_soc.h"
>> >> +#include "mtk_wed.h"
>> >>  
>> >>  struct mtk_flow_data {
>> >>  	struct ethhdr eth;
>> >> @@ -39,6 +40,7 @@ struct mtk_flow_entry {
>> >>  	struct rhash_head node;
>> >>  	unsigned long cookie;
>> >>  	u16 hash;
>> >> +	s8 wed_index;
>> >>  };
>> >>  
>> >>  static const struct rhashtable_params mtk_flow_ht_params = {
>> >> @@ -127,35 +129,38 @@ mtk_flow_mangle_ipv4(const struct flow_action_entry *act,
>> >>  }
>> >>  
>> >>  static int
>> >> -mtk_flow_get_dsa_port(struct net_device **dev)
>> >> +mtk_flow_set_output_device(struct mtk_eth *eth, struct mtk_foe_entry *foe,
>> >> +			   struct net_device *dev, const u8 *dest_mac,
>> >> +			   int *wed_index)
>> >>  {
>> >> -#if IS_ENABLED(CONFIG_NET_DSA)
>> >> -	struct dsa_port *dp;
>> >> -
>> >> -	dp = dsa_port_from_netdev(*dev);
>> >> -	if (IS_ERR(dp))
>> >> -		return -ENODEV;
>> >> -
>> >> -	if (dp->cpu_dp->tag_ops->proto != DSA_TAG_PROTO_MTK)
>> >> -		return -ENODEV;
>> >> +	struct net_device_path_ctx ctx = {
>> >> +		.dev    = dev,
>> >> +		.daddr  = dest_mac,
>> >> +	};
>> >> +	struct net_device_path path = {};
>> >> +	int pse_port;
>> >>  
>> >> -	*dev = dp->cpu_dp->master;
>> >> +	if (!dev->netdev_ops->ndo_fill_forward_path ||
>> >> +	    dev->netdev_ops->ndo_fill_forward_path(&ctx, &path) < 0)
>> >> +		path.type = DEV_PATH_ETHERNET;
>> > 
>> > Maybe expose this through flow offload API so there is no need to call
>> > ndo_fill_forward_path again from the driver?
>>
>> Can you give me a pseudo-code example? I'm not sure how you want it to
>> be exposed through the flow offload API.
> 
> in a few steps:
> 
> 1) Extend nft_dev_path_info() to deal with DEV_PATH_WDMA, it will
>    just actually fetch a pointer to structure that is allocated
>    by the driver.
> 
> - Update the net_device_path structure with this layout:
> 
>         struct flow_action_wdma {
>                 enum wdma_type type;    // MTK_WDMA goes here
>                 union {
>                         struct {
>                                 ...;
>                         } mtk;
>                 };
>         } wdma;
> 
> Add:
>         struct flow_action_wdma         *wdma;
> 
> to net_device_path.
> 
> 2) Pass on this pointer to structure to the nf_flow_route
>    wheelbarrow.
> 
> 3) Store this information in the struct flow_offload_tuple,
>    in a new struct flow_offload_hw *field to store all hardware
>    offload specific information (not needed by software path). There
>    is already hw_outdev that can be placed there.
> 
> 4) Add a FLOW_ACTION_WDMA action to the flow offload API to
>    pass on the flow_action_wdma structure.
I think it should probably be called FLOW_ACTION_MTK_WDMA (and be
mediatek specific), or we should pick a more generic name for it.

> It's a bit of work the first time to accomodate the requirements of
> new API, but then all drivers will benefit from this.
> 
> It's also a bit of layering, but with more drivers in the tree, this
> API can be simplified incrementally.
> 
> I can take a stab at it and send you a patch.
Thanks. If we do this for WDMA, shouldn't we also do it for DSA to keep
things consistent?

- Felix