Re: [PATCH,v2] wifi: mt76: mt7915: add wds support when wed is enabled

[Felix Fietkau <nbd@nbd.name>]

On 30.11.22 10:18, Sujuan Chen wrote:
> The current WED only supports 256 wcid, whereas mt7986 can support up to 512 entries,
> so firmware provides a rule to get sta_info by DA when wcid is set to 0x3ff by txd.
> Also, WED provides a register to overwrite txd wcid, that is, wcid[9:8] can
> be overwritten by 0x3 and wcid[7:0] is set to 0xff by host driver.
> 
> However, firmware is unable to get sta_info from DA as DA != RA for 4addr cases,
> so firmware and wifi host driver both use wcid (256 - 271) and (768 ~ 783)
> for sync up to get correct sta_info
> 
> Tested-by: Sujuan Chen <sujuan.chen@mediatek.com>
> Co-developed-by: Bo Jiao <bo.jiao@mediatek.com>
> Signed-off-by: Bo Jiao <bo.jiao@mediatek.com>
> Signed-off-by: Sujuan Chen <sujuan.chen@mediatek.com>
> ---
> v2:
>   - drop duplicate settings
>   - reduce the patch size by redefining mt76_wcid_alloc
> ---
>   drivers/net/wireless/mediatek/mt76/mt76.h     |  6 +++
>   .../net/wireless/mediatek/mt76/mt7915/main.c  | 24 +++++++++--
>   .../net/wireless/mediatek/mt76/mt7915/mcu.c   | 13 +++++-
>   .../net/wireless/mediatek/mt76/mt7915/mcu.h   |  1 +
>   drivers/net/wireless/mediatek/mt76/util.c     | 40 +++++++++++++++++--
>   drivers/net/wireless/mediatek/mt76/util.h     |  7 +++-
>   6 files changed, 82 insertions(+), 9 deletions(-)
> 

> diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/main.c b/drivers/net/wireless/mediatek/mt76/mt7915/main.c
> index c40b6098f19a..46a9e4f0396e 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7915/main.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7915/main.c
> @@ -1115,6 +1122,13 @@ static void mt7915_sta_set_4addr(struct ieee80211_hw *hw,
>   	else
>   		clear_bit(MT_WCID_FLAG_4ADDR, &msta->wcid.flags);
>   
> +	if (mtk_wed_device_active(&dev->mt76.mmio.wed) &&
> +	    !is_mt7915(&dev->mt76)) {
> +		mt7915_sta_remove(hw, vif, sta);
> +		mt76_sta_pre_rcu_remove(hw, vif, sta);
> +		mt7915_sta_add(hw, vif, sta);
> +	}
> +
>   	mt76_connac_mcu_wtbl_update_hdr_trans(&dev->mt76, vif, sta);
>   }
>   
I suspect that this may a bit racy if there is concurrent tx activity 
(e.g. for EAP auth). Not sure if this could cause problems for the 
firmware or other kinds of bugs.

While my idea may need some rework of the existing functions, I think a 
better flow would be:

1. mt76_sta_pre_rcu_remove
2. save old wcid
3. mt7915_sta_add
4. synchronize_rcu()
5. remove firmware state for old wcid entry

- Felix