staging: wfx: fix QoS priority for slow buses (0d2dfdb8) · Commits · 戴 / test

The device is in charge of respecting the QoS constraints. The driver have to ensure that all the queues contain data and the device choose the right queue to send. The things starts to be more difficult when the bandwidth of the bus is lower than the bandwidth of the WiFi. The device quickly sends the frames of the highest priority queue. Then, it starts to send frames from a lower priority queue. Though, there are still some high priority frames waiting in the driver. To work around this problem, this patch add some priorities to each queue. The weigh of the queue was (roughly) calculated experimentally by checking the speed ratio of each queue when the bus does not limit the traffic: - Be/Bk -> 20Mbps/10Mbps - Vi/Be -> 36Mbps/180Kbps - Vo/Be -> 35Mbps/600Kbps - Vi/Vo -> 24Mbps/12Mbps So, if we fix the weigh of the Background to 1, the weight of Best Effort should be 2. The weight of Video should be 116. However, since there is only 32 queues, it make no sense to use a value greater than 64[1]. And finally, the weight of the Voice is set to 128. [1] Because of this approximation, with very slow bus, we can still observe frame starvation when we measure the speed ratio of Vi/Be. It is around 35Mbps/1Mbps (instead of 36Mbps/180Kbps). However, it is still in accepted error range. Signed-off-by:

Jérôme Pouiller <jerome.pouiller@silabs.com> Link: https://lore.kernel.org/r/20201007101943.749898-5-Jerome.Pouiller@silabs.com Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/queue.c

+12 −2

Original line number	Diff line number	Diff line
		@@ -60,11 +60,16 @@ void wfx_tx_lock_flush(struct wfx_dev *wdev)

		void wfx_tx_queues_init(struct wfx_vif *wvif)
		{
		// The device is in charge to respect the details of the QoS parameters.
		// The driver just ensure that it roughtly respect the priorities to
		// avoid any shortage.
		const int priorities[IEEE80211_NUM_ACS] = { 1, 2, 64, 128 };
		int i;

		for (i = 0; i < IEEE80211_NUM_ACS; ++i) {
		skb_queue_head_init(&wvif->tx_queue[i].normal);
		skb_queue_head_init(&wvif->tx_queue[i].cab);
		wvif->tx_queue[i].priority = priorities[i];
		}
		}

		@@ -219,6 +224,11 @@ bool wfx_tx_queues_has_cab(struct wfx_vif *wvif)
		return false;
		}

		static int wfx_tx_queue_get_weight(struct wfx_queue *queue)
		{
		return atomic_read(&queue->pending_frames) * queue->priority;
		}

		static struct sk_buff wfx_tx_queues_get_skb(struct wfx_dev wdev)
		{
		struct wfx_queue queues[IEEE80211_NUM_ACS ARRAY_SIZE(wdev->vif)];
		@@ -234,8 +244,8 @@ static struct sk_buff wfx_tx_queues_get_skb(struct wfx_dev wdev)
		WARN_ON(num_queues >= ARRAY_SIZE(queues));
		queues[num_queues] = &wvif->tx_queue[i];
		for (j = num_queues; j > 0; j--)
		if (atomic_read(&queues[j]->pending_frames) <
		atomic_read(&queues[j - 1]->pending_frames))
		if (wfx_tx_queue_get_weight(queues[j]) <
		wfx_tx_queue_get_weight(queues[j - 1]))
		swap(queues[j - 1], queues[j]);
		num_queues++;
		}

drivers/staging/wfx/queue.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -18,6 +18,7 @@ struct wfx_queue {
		struct sk_buff_head normal;
		struct sk_buff_head cab; // Content After (DTIM) Beacon
		atomic_t pending_frames;
		int priority;
		};

		void wfx_tx_lock(struct wfx_dev *wdev);

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