Re: [PATCH 2/3] carlfw: wlanrx: batch RX frame upload triggers

[Christian Lamparter <chunkeey@gmail.com>]

On 3/17/26 10:11 AM, iamdevnull wrote:
> From: Masi Osmani <mas-i@hotmail.de>
> 
> Call up_trigger() once after processing all pending RX descriptors
> instead of per-frame. The PTA DMA transfers all queued descriptors
> in a single USB transaction, reducing interrupt overhead on the host
> by up to N (where N = frames per RX burst).
> 
> On a busy 2.4 GHz channel with 10+ APs visible, this reduces USB
> interrupt rate during scan sweeps from ~200/s to ~30/s.

Interesting. Are you willing to share what PC/device you connected
your Fritz!WLAN N adapter to?

Because yes, I tried this before and I didn't see such a big difference.
This was back with my AMD Athlon X2, Core2Duo T7200 and i7 2630qm, It
became irrelevant with the i7 4770 (which I still have... but with a
new 2018-ish MB).

Cheers,
Christian


> Signed-off-by: Masi Osmani <mas-i@hotmail.de>
> ---
>   carlfw/src/wlanrx.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/carlfw/src/wlanrx.c b/carlfw/src/wlanrx.c
> index 1234567..abcdefg 100644
> --- a/carlfw/src/wlanrx.c
> +++ b/carlfw/src/wlanrx.c
> @@ -160,14 +160,24 @@
>   void handle_wlan_rx(void)
>   {
>   	struct dma_desc *desc;
> +	bool queued = false;
> 
>   	for_each_desc_not_bits(desc, &fw.wlan.rx_queue, AR9170_OWN_BITS_HW) {
>   		if (!(wlan_rx_filter(desc) & fw.wlan.rx_filter)) {
>   			dma_put(&fw.pta.up_queue, desc);
> -			up_trigger();
> +			queued = true;
>   		} else {
>   			dma_reclaim(&fw.wlan.rx_queue, desc);
>   			wlan_trigger(AR9170_DMA_TRIGGER_RXQ);
>   		}
>   	}
> +
> +	/*
> +	 * Trigger USB upload once for the entire batch rather than
> +	 * per frame.  The PTA DMA will transfer all queued descriptors
> +	 * in a single USB transaction, reducing interrupt overhead on
> +	 * the host by up to N (where N = frames per RX burst).
> +	 */
> +	if (queued)
> +		up_trigger();
>   }