Re: [PATCH v6] wifi: mt76: mt7915: add wds support when wed is enabled

[Shengyu Qu <wiagn233@outlook.com>]

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>> diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/main.c 
>> b/drivers/net/wireless/mediatek/mt76/mt7915/main.c
>> index 049223df9beb1..dc4d87e004a0f 100644
>> --- a/drivers/net/wireless/mediatek/mt76/mt7915/main.c
>> +++ b/drivers/net/wireless/mediatek/mt76/mt7915/main.c
>> @@ -745,8 +745,15 @@ int mt7915_mac_sta_add(struct mt76_dev *mdev, 
>> struct ieee80211_vif *vif,
>>       bool ext_phy = mvif->phy != &dev->phy;
>>       int ret, idx;
>>       u32 addr;
>> +    u8 flags = MT76_WED_DEFAULT;
>> -    idx = mt76_wcid_alloc(dev->mt76.wcid_mask, MT7915_WTBL_STA);
>> +    if (mtk_wed_device_active(&dev->mt76.mmio.wed) &&
>> +        !is_mt7915(&dev->mt76)) {
>> +        flags = test_bit(MT_WCID_FLAG_4ADDR, &msta->wcid.flags) ?
>> +               MT76_WED_WDS_ACTIVE : MT76_WED_ACTIVE;
>> +    }
>> +
>> +    idx = __mt76_wcid_alloc(mdev->wcid_mask, MT7915_WTBL_STA, flags);
>>       if (idx < 0)
>>           return -ENOSPC;
> 
> I'd prefer to replace the mt76_wcid_alloc flags argument with an 
> explicit start offset argument.

Hi Felix,

I'm not really familiar with mt76 code, just a enthusiast that wants to
make WDS+WED working. So I'm not sure how to do this correctly... Maybe
it's better for you to take over this patch, sorry.

>> @@ -1201,12 +1208,27 @@ static void mt7915_sta_set_4addr(struct 
>> ieee80211_hw *hw,
>>   {
>>       struct mt7915_dev *dev = mt7915_hw_dev(hw);
>>       struct mt7915_sta *msta = (struct mt7915_sta *)sta->drv_priv;
>> +    int min = MT76_WED_WDS_MIN, max = MT76_WED_WDS_MAX;
>>       if (enabled)
>>           set_bit(MT_WCID_FLAG_4ADDR, &msta->wcid.flags);
>>       else
>>           clear_bit(MT_WCID_FLAG_4ADDR, &msta->wcid.flags);
>> +    if (mtk_wed_device_active(&dev->mt76.mmio.wed) &&
>> +        !is_mt7915(&dev->mt76) &&
>> +        (msta->wcid.idx < min || msta->wcid.idx > max - 1)) {
>> +        struct ieee80211_sta *pre_sta;
>> +
>> +        pre_sta = kzalloc(sizeof(*sta) + sizeof(*msta), GFP_KERNEL);
>> +        mt76_sta_pre_rcu_remove(hw, vif, sta);
>> +        memmove(pre_sta, sta, sizeof(*sta) + sizeof(*msta));
>> +        mt7915_sta_add(hw, vif, sta);
>> +        synchronize_rcu();
>> +        mt7915_sta_remove(hw, vif, pre_sta);
>> +        kfree(pre_sta);
>> +    }
>> +
>>       mt76_connac_mcu_wtbl_update_hdr_trans(&dev->mt76, vif, sta);
>>   }
>>
> In order to update the code based on my latest changes and to fix 
> potential race conditions on tx/rx packets during the transition, please 
> change to this order:
> 
> 1. copy the sta
> 2. allocate a new wcid
> 3. change the wcid index in the copied sta to the newly allocated wcid
> 4. call mcu functions on the duplicate sta for creating the new sta entry.
> 5. use rcu_assign_pointer to point dev->wcid[new_idx] at &msta->wcid
> 6. swap wcid index between real sta and duplicated sta
> 7. rcu_assign_pointer(dev->wcid[orig_idx], NULL)
> 8. synchronize_rcu()
> 9. call mcu functions to delete the duplicate sta's entry (points to old 
> wcid after the swap)
> 10. free the duplicated sta

Now, the mt7915_sta_set_4addr function looks like this(__mt76_wcid_alloc
not modified), do you think it's acceptable?

static void mt7915_sta_set_4addr(struct ieee80211_hw *hw,
				 struct ieee80211_vif *vif,
				 struct ieee80211_sta *sta,
				 bool enabled)
{
	struct mt7915_dev *dev = mt7915_hw_dev(hw);
	struct mt7915_sta *msta = (struct mt7915_sta *)sta->drv_priv;
	int min = MT76_WED_WDS_MIN, max = MT76_WED_WDS_MAX;
	struct ieee80211_sta *pre_sta;
	u8 flags = MT76_WED_DEFAULT;
	int temp_idx;

	if (enabled)
		set_bit(MT_WCID_FLAG_4ADDR, &msta->wcid.flags);
	else
		clear_bit(MT_WCID_FLAG_4ADDR, &msta->wcid.flags);

	if (!msta->wcid.sta)
		return;

	if (mtk_wed_device_active(&dev->mt76.mmio.wed) &&
	    !is_mt7915(&dev->mt76) &&
	    (msta->wcid.idx < min || msta->wcid.idx > max - 1)) {
		pre_sta = kzalloc(sizeof(*sta) + sizeof(*msta), GFP_KERNEL);
		memmove(pre_sta, sta, sizeof(*sta) + sizeof(*msta));
		if (mtk_wed_device_active(&dev->mt76.mmio.wed) &&
			!is_mt7915(&dev->mt76)) {
			flags = test_bit(MT_WCID_FLAG_4ADDR, &msta->wcid.flags) ?
				MT76_WED_WDS_ACTIVE : MT76_WED_ACTIVE;
		}

		temp_idx = __mt76_wcid_alloc(mdev->wcid_mask, MT7915_WTBL_STA, flags);
		((struct mt7915_sta *)pre_sta->drv_priv)->wcid.idx = temp_idx;
		mt7915_sta_add(hw, vif, pre_sta);
		rcu_assign_pointer(dev->mt76.wcid[temp_idx], &msta->wcid);
		temp_idx = msta->wcid.idx;
		msta->wcid.idx = ((struct mt7915_sta *)pre_sta->drv_priv)->wcid.idx;
		((struct mt7915_sta *)pre_sta->drv_priv)->wcid.idx = temp_idx;
		rcu_assign_pointer(dev->mt76.wcid[temp_idx], NULL);
		synchronize_rcu();
		mt7915_sta_remove(hw, vif, pre_sta);
		kfree(pre_sta);
	}

	mt76_connac_mcu_wtbl_update_hdr_trans(&dev->mt76, vif, sta);
}

Best regards,
Shengyu

> This should allow mgmt tx/rx to work while the sta is being migrated to 
> the new wcid entry.
> 
> - Felix

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