Re: [RFC V3] bcm43xx-mac80211: Provide information to allow transmission rate decreases

[Michael Buesch <mb@bu3sch.de>]

On Thursday 02 August 2007, Larry Finger wrote:
> Michael,
> 
> I couldn't find any long/short indication in the header, so I added a bool that
> is set when the frame is sent.

This is not going to work.

But we can do this differently.
You can do something like:

if (!status->acked && !tx_control->noack)
	excessive_retries = 1;

So we don't need to care about the retry count.

Anyway. I don't know why we need excessive_retries _at_ _all_.
The rc algorithm does already know if the frame succeed or failed
anyway.

/me shrugs

> Larry
> ---
> 
> In bcm43xx-mac80211, the mechanism for decreasing the transmit rate cannot
> be triggered. This may be shown by walking away from the AP with a laptop.
> At some distance, communications will be lost and never recovered because
> the rate decreasing mechanism of rc80211_simple needs to see excessive_retries
> set in the ieee80211_tx_status struct. With this patch, the transmit rate
> will decrease until communications restart.
> 
> Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
> ---
> 
> Index: wireless-dev/drivers/net/wireless/bcm43xx-mac80211/bcm43xx_dma.c
> ===================================================================
> --- wireless-dev.orig/drivers/net/wireless/bcm43xx-mac80211/bcm43xx_dma.c
> +++ wireless-dev/drivers/net/wireless/bcm43xx-mac80211/bcm43xx_dma.c
> @@ -1311,6 +1311,16 @@ void bcm43xx_dma_handle_txstatus(struct 
>  			 */
>  			if (status->acked)
>  				meta->txstat.flags |= IEEE80211_TX_STATUS_ACK;
> +			else
> +				if (dev->last_frame_long) {
> +					if (status->frame_count >=
> +					    dev->long_retry_limit)
> +						meta->txstat.excessive_retries = 1;
> +				} else {
> +					if (status->frame_count >=
> +					    dev->short_retry_limit)
> +						meta->txstat.excessive_retries = 1;
> +				}
>  			meta->txstat.retry_count = status->frame_count - 1;
>  			ieee80211_tx_status_irqsafe(dev->wl->hw, meta->skb, &(meta->txstat));
>  			/* skb is freed by ieee80211_tx_status_irqsafe() */
> Index: wireless-dev/drivers/net/wireless/bcm43xx-mac80211/bcm43xx.h
> ===================================================================
> --- wireless-dev.orig/drivers/net/wireless/bcm43xx-mac80211/bcm43xx.h
> +++ wireless-dev/drivers/net/wireless/bcm43xx-mac80211/bcm43xx.h
> @@ -707,6 +707,9 @@ struct bcm43xx_wldev {
>  	bool short_preamble;		/* TRUE, if short preamble is enabled. */
>  	bool short_slot;		/* TRUE, if short slot timing is enabled. */
>  	bool radio_hw_enable;		/* saved state of radio hardware enabled state */
> +	bool last_frame_long;		/* true is last frame was long */
> +	u8 short_retry_limit;
> +	u8 long_retry_limit;
>  
>  	/* PHY/Radio device. */
>  	struct bcm43xx_phy phy;
> Index: wireless-dev/drivers/net/wireless/bcm43xx-mac80211/bcm43xx_main.c
> ===================================================================
> --- wireless-dev.orig/drivers/net/wireless/bcm43xx-mac80211/bcm43xx_main.c
> +++ wireless-dev/drivers/net/wireless/bcm43xx-mac80211/bcm43xx_main.c
> @@ -3333,10 +3333,12 @@ static int bcm43xx_wireless_core_init(st
>  	tmp = limit_value(modparam_short_retry, 0, 0xF);
>  	bcm43xx_shm_write16(dev, BCM43xx_SHM_SCRATCH,
>  			    BCM43xx_SHM_SC_SRLIMIT, tmp);
> +	dev->short_retry_limit = tmp;
>  	tmp = limit_value(modparam_long_retry, 0, 0xF);
>  	bcm43xx_shm_write16(dev, BCM43xx_SHM_SCRATCH,
>  			    BCM43xx_SHM_SC_LRLIMIT, tmp);
>  
> +	dev->long_retry_limit = tmp;
>  	bcm43xx_shm_write16(dev, BCM43xx_SHM_SHARED,
>  			    BCM43xx_SHM_SH_SFFBLIM, 3);
>  	bcm43xx_shm_write16(dev, BCM43xx_SHM_SHARED,
> Index: wireless-dev/drivers/net/wireless/bcm43xx-mac80211/bcm43xx_xmit.c
> ===================================================================
> --- wireless-dev.orig/drivers/net/wireless/bcm43xx-mac80211/bcm43xx_xmit.c
> +++ wireless-dev/drivers/net/wireless/bcm43xx-mac80211/bcm43xx_xmit.c
> @@ -264,6 +264,7 @@ static void generate_txhdr_fw4(struct bc
>  	 * is a 5Ghz packet.
>  	 */
>  	txhdr->chan_radio_code = phy->channel;
> +	dev->last_frame_long = 0;
>  
>  	/* PHY TX Control word */
>  	if (rate_ofdm)
> @@ -336,6 +337,7 @@ static void generate_txhdr_fw4(struct bc
>  		if (rts_rate_fb_ofdm)
>  			extra_ft |= BCM43xx_TX4_EFT_RTSFBOFDM;
>  		mac_ctl |= BCM43xx_TX4_MAC_LONGFRAME;
> +		dev->last_frame_long = 1;
>  	}
>  
>  	/* Magic cookie */
> 
>