[Intel-wired-lan] [PATCH v2] fm10k: drop transmitted messages in Tx FIFO as part of reset_work

[Keller, Jacob E <jacob.e.keller@intel.com>]

On Thu, 2015-06-25 at 14:29 -0700, Jacob Keller wrote:
> This patch fixes a corner case issue with the PF/VF mailbox code.
> Currently, fm10k_mbx_reset_work clears various state about the 
> mailbox.
> However, it does not clear the Tx FIFO head/tail pointers. We can't
> simply clear these pointers as we unintentionally drop untransmitted
> messages without error.
> 
> Doing nothing results in a possible phantom re-transmission of 
> messages,
> since we leave tx.head and tx.tail intact, but clear the tx_pulled 
> and
> tail_len values. This means that the PF could continuously re-send a
> message which triggers a reset in the VF. Upon reset, the VF will
> re-receive the same message after a reconnect.
> 
> If we reset the tx.head and tx.tail pointers completely, we end up
> dropping some messages that were pending before connect. This results 
> in
> missing LPORT_MSG_READY bits, and VFs will end up reporting no link.
> 
> However, we can resolve both issues by simply incrementing head to
> account for the already transmitted messages, before we reset 
> tx_pulled.
> We do this via the same logic as fm10k_mbx_head_pull.
> 
> We account for the tail_len which includes all data not yet 
> transmitted,
> once we account for the acked data which means re-reading the HEAD
> variable from the message header. Then, we drop messages until we've
> dropped more than the new tx_pulled value. At this point, resetting
> tail_len and tx_pulled, but not tx.head and tx.tail will result in
> prevention of the phantom message. It also prevents us from dropping
> untransmitted messages upon attempting to Tx into a connect or
> disconnect header.
> 
> Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
> ---
>  drivers/net/ethernet/intel/fm10k/fm10k_mbx.c | 21 
> +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_mbx.c 
> b/drivers/net/ethernet/intel/fm10k/fm10k_mbx.c
> index 1a4b52637de9..a86299ecbb70 100644
> --- a/drivers/net/ethernet/intel/fm10k/fm10k_mbx.c
> +++ b/drivers/net/ethernet/intel/fm10k/fm10k_mbx.c
> @@ -132,7 +132,7 @@ static u16 fm10k_fifo_head_drop(struct 
> fm10k_mbx_fifo *fifo)
>   *  This function resets the head pointer to drop all messages in 
> the FIFO,
>   *  and ensure the FIFO is empty.
>   **/
> -static void fm10k_fifo_drop_all(struct fm10k_mbx_fifo *fifo)
> +STATIC void fm10k_fifo_drop_all(struct fm10k_mbx_fifo *fifo)
>  {

Woops this shouldn't have happened. Sending a fixed version.

Regards

>  	fifo->head = fifo->tail;
>  }
> @@ -1046,9 +1046,26 @@ static s32 fm10k_mbx_create_reply(struct 
> fm10k_hw *hw,
>   **/
>  static void fm10k_mbx_reset_work(struct fm10k_mbx_info *mbx)
>  {
> +	u16 len, head, ack;
> +
>  	/* reset our outgoing max size back to Rx limits */
>  	mbx->max_size = mbx->rx.size - 1;
>  
> +	/* update mbx->pulled to account for tail_len and ack */
> +	head = FM10K_MSG_HDR_FIELD_GET(mbx->mbx_hdr, HEAD);
> +	ack = fm10k_mbx_index_len(mbx, head, mbx->tail);
> +	mbx->pulled += mbx->tail_len - ack;
> +
> +	/* now drop any messages which have started or finished 
> transmitting */
> +	while (fm10k_fifo_head_len(&mbx->tx) && mbx->pulled) {
> +		len = fm10k_fifo_head_drop(&mbx->tx);
> +		mbx->tx_dropped++;
> +		if (mbx->pulled >= len)
> +			mbx->pulled -= len;
> +		else
> +			mbx->pulled = 0;
> +	}
> +
>  	/* just do a quick resysnc to start of message */
>  	mbx->pushed = 0;
>  	mbx->pulled = 0;
> @@ -1725,7 +1742,7 @@ static void fm10k_sm_mbx_disconnect(struct 
> fm10k_hw *hw,
>  	mbx->state = FM10K_STATE_CLOSED;
>  	mbx->remote = 0;
>  	fm10k_mbx_reset_work(mbx);
> -	fm10k_mbx_update_max_size(mbx, 0);
> +	fm10k_fifo_drop_all(&mbx->tx);
>  
>  	fm10k_write_reg(hw, mbx->mbmem_reg, 0);
>  }