[PATCH] Back off if ring buffer is full

[Eugene Krasnikov]

This is a patch for the bug https://github.com/KrasnikovEugene/wcn36xx/issues/83

Pull request: https://github.com/KrasnikovEugene/wcn36xx/pull/85

2013/7/16 Eugene Krasnikov <k.eugene.e at gmail.com>:
> If ring is full stop mac80211 queues so upper layers will not try to
> send any frames until bottom half has capacity for sending frames.
>
> Signed-off-by: Eugene Krasnikov <k.eugene.e at gmail.com>
> ---
>  dxe.c     | 22 ++++++++++++++++++++++
>  dxe.h     |  1 +
>  wcn36xx.h |  1 +
>  3 files changed, 24 insertions(+)
>
> diff --git a/dxe.c b/dxe.c
> index fd6cbae..502e0df 100644
> --- a/dxe.c
> +++ b/dxe.c
> @@ -319,6 +319,7 @@ static void reap_tx_dxes(struct wcn36xx *wcn, struct wcn36xx_dxe_ch *ch)
>  {
>         struct wcn36xx_dxe_ctl *ctl = ch->tail_blk_ctl;
>         struct ieee80211_tx_info *info;
> +       unsigned long flags;
>
>         while (ctl != ch->head_blk_ctl &&
>                !(ctl->desc->ctrl & WCN36XX_DXE_CTRL_VALID_MASK)) {
> @@ -330,6 +331,13 @@ static void reap_tx_dxes(struct wcn36xx *wcn, struct wcn36xx_dxe_ch *ch)
>                                 /* Keep frame until TX status comes */
>                                 ieee80211_free_txskb(wcn->hw, ctl->skb);
>                         }
> +                       spin_lock_irqsave(&ctl->skb_lock, flags);
> +                       if (wcn->queues_stopped) {
> +                               wcn->queues_stopped = false;
> +                               ieee80211_wake_queues(wcn->hw);
> +                       }
> +                       spin_unlock_irqrestore(&ctl->skb_lock, flags);
> +
>                         ctl->skb = NULL;
>                 }
>                 ctl = ctl->next;
> @@ -539,10 +547,24 @@ int wcn36xx_dxe_tx_frame(struct wcn36xx *wcn,
>         struct wcn36xx_dxe_ctl *ctl = NULL;
>         struct wcn36xx_dxe_desc *desc = NULL;
>         struct wcn36xx_dxe_ch *ch = NULL;
> +       unsigned long flags;
>
>         ch = is_low ? &wcn->dxe_tx_l_ch : &wcn->dxe_tx_h_ch;
>
>         ctl = ch->head_blk_ctl;
> +       spin_lock_irqsave(&ctl->next->skb_lock, flags);
> +       /*
> +        * If skb is not null that means that we reached the tail of the ring
> +        * hence ring is full. Stop queues to let mac80211 back off until ring
> +        * has an empty slot again.
> +        */
> +       if (NULL != ctl->next->skb) {
> +               ieee80211_stop_queues(wcn->hw);
> +               wcn->queues_stopped = true;
> +               spin_unlock_irqrestore(&ctl->next->skb_lock, flags);
> +               return -EBUSY;
> +       }
> +       spin_unlock_irqrestore(&ctl->next->skb_lock, flags);
>         ctl->skb = NULL;
>         desc = ctl->desc;
>
> diff --git a/dxe.h b/dxe.h
> index 0b154bb..16f0b12 100644
> --- a/dxe.h
> +++ b/dxe.h
> @@ -195,6 +195,7 @@ struct wcn36xx_dxe_ctl {
>         unsigned int            desc_phy_addr;
>         int                     ctl_blk_order;
>         struct sk_buff          *skb;
> +       spinlock_t              skb_lock;
>         void                    *bd_cpu_addr;
>         dma_addr_t              bd_phy_addr;
>  };
> diff --git a/wcn36xx.h b/wcn36xx.h
> index 743325e..ff349ea 100644
> --- a/wcn36xx.h
> +++ b/wcn36xx.h
> @@ -166,6 +166,7 @@ struct wcn36xx {
>
>         /* For synchronization of DXE resources from BH, IRQ and WQ contexts */
>         spinlock_t      dxe_lock;
> +       bool                    queues_stopped;
>
>         /* Memory pools */
>         struct wcn36xx_dxe_mem_pool mgmt_mem_pool;
> --
> 1.7.11.3
>



-- 
Best regards,
Eugene