[RFC][PATCH] b43: do not try sending packets when ring can be full

[Michael Büsch]

On Sun, 12 Jun 2011 17:11:53 +0200
Rafał Miłecki <zajec5 at gmail.com> wrote:

> ---
> This prevents us from hitting "Packet after queue stopped", but still
> is not an optimal solution. We stop sending packets from queue to
> hardware if just a one ring is full. It may happen there are packets on
> the queue that want to be send to different ring (qos).
> ---
>  drivers/net/wireless/b43/b43.h  |    2 ++
>  drivers/net/wireless/b43/dma.c  |    5 +++++
>  drivers/net/wireless/b43/main.c |    5 +++++
>  3 files changed, 12 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/wireless/b43/b43.h b/drivers/net/wireless/b43/b43.h
> index 1cb2dde..8d4bb28 100644
> --- a/drivers/net/wireless/b43/b43.h
> +++ b/drivers/net/wireless/b43/b43.h
> @@ -582,6 +582,8 @@ struct b43_dma {
>  	struct b43_dmaring *rx_ring;
>  
>  	u32 translation; /* Routing bits */
> +
> +	u8 stopped_rings; /* Amount of stopped rings */
>  };
>  
>  struct b43_pio_txqueue;
> diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
> index d02cf83..a501992 100644
> --- a/drivers/net/wireless/b43/dma.c
> +++ b/drivers/net/wireless/b43/dma.c
> @@ -1056,6 +1056,7 @@ int b43_dma_init(struct b43_wldev *dev)
>  	if (err)
>  		return err;
>  	dma->translation = ssb_dma_translation(dev->sdev);
> +	dma->stopped_rings = 0;
>  
>  	err = -ENOMEM;
>  	/* setup TX DMA channels. */
> @@ -1374,6 +1375,8 @@ int b43_dma_tx(struct b43_wldev *dev, struct sk_buff *skb)
>  		/* This TX ring is full. */
>  		ieee80211_stop_queue(dev->wl->hw, skb_get_queue_mapping(skb));
>  		ring->stopped = 1;
> +		dev->dma.stopped_rings++;
> +
>  		if (b43_debug(dev, B43_DBG_DMAVERBOSE)) {
>  			b43dbg(dev->wl, "Stopped TX ring %d\n", ring->index);
>  		}
> @@ -1493,9 +1496,11 @@ void b43_dma_handle_txstatus(struct b43_wldev *dev,
>  		B43_WARN_ON(free_slots(ring) < TX_SLOTS_PER_FRAME);
>  		ieee80211_wake_queue(dev->wl->hw, ring->queue_prio);
>  		ring->stopped = 0;
> +		dev->dma.stopped_rings--;
>  		if (b43_debug(dev, B43_DBG_DMAVERBOSE)) {
>  			b43dbg(dev->wl, "Woke up TX ring %d\n", ring->index);
>  		}
> +		ieee80211_queue_work(dev->wl->hw, &dev->wl->tx_work);
>  	}
>  }
>  
> diff --git a/drivers/net/wireless/b43/main.c b/drivers/net/wireless/b43/main.c
> index 1d8d983..2260b36 100644
> --- a/drivers/net/wireless/b43/main.c
> +++ b/drivers/net/wireless/b43/main.c
> @@ -3219,6 +3219,11 @@ static void b43_tx_work(struct work_struct *work)
>  	}
>  
>  	while (skb_queue_len(&wl->tx_queue)) {
> +		if (!b43_using_pio_transfers(dev) && dev->dma.stopped_rings) {
> +			mutex_unlock(&wl->mutex);
> +			return;
> +		}
> +
>  		skb = skb_dequeue(&wl->tx_queue);
>  
>  		if (b43_using_pio_transfers(dev))

This can probably serve as a quick workaround, as long as a real fix is being developed.

I'm not sure if multiple queues are needed for this to work. I think it could work
with a single queue as well. We just must not _unqueue_ it, if we are unable to transmit
it due to stopped ring. I don't know if there are skb_queue mechanisms that help
us achieve this.