Subject: Re: [RFC 06/19] staging: qlge: disable flow control by default

From: Benjamin Poirier <[email-masked]>
Date: Tue, 22 Jun 2021 16:49:51 +0900

On 2021-06-21 21:48 +0800, Coiby Xu wrote:
> According to the TODO item,
> > * the flow control implementation in firmware is buggy (sends a flood of pause
> >   frames, resets the link, device and driver buffer queues become
> >   desynchronized), disable it by default
> 
> Currently, qlge_mpi_port_cfg_work calls qlge_mb_get_port_cfg which gets
> the link config from the firmware and saves it to qdev->link_config. By
> default, flow control is enabled. This commit writes the
> save the pause parameter of qdev->link_config and don't let it
> overwritten by link settings of current port. Since qdev->link_config=0
> when qdev is initialized, this could disable flow control by default and
> the pause parameter value could also survive MPI resetting,
>     $ ethtool -a enp94s0f0
>     Pause parameters for enp94s0f0:
>     Autonegotiate:  off
>     RX:             off
>     TX:             off
> 
> The follow control can be enabled manually,
> 
>     $ ethtool -A enp94s0f0 rx on tx on
>     $ ethtool -a enp94s0f0
>     Pause parameters for enp94s0f0:
>     Autonegotiate:  off
>     RX:             on
>     TX:             on
> 
> Signed-off-by: Coiby Xu <[email-masked]>
> ---
>  drivers/staging/qlge/TODO       |  3 ---
>  drivers/staging/qlge/qlge_mpi.c | 11 ++++++++++-
>  2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/qlge/TODO b/drivers/staging/qlge/TODO
> index b7a60425fcd2..8c84160b5993 100644
> --- a/drivers/staging/qlge/TODO
> +++ b/drivers/staging/qlge/TODO
> @@ -4,9 +4,6 @@
>    ql_build_rx_skb(). That function is now used exclusively to handle packets
>    that underwent header splitting but it still contains code to handle non
>    split cases.
> -* the flow control implementation in firmware is buggy (sends a flood of pause
> -  frames, resets the link, device and driver buffer queues become
> -  desynchronized), disable it by default
>  * some structures are initialized redundantly (ex. memset 0 after
>    alloc_etherdev())
>  * the driver has a habit of using runtime checks where compile time checks are
> diff --git a/drivers/staging/qlge/qlge_mpi.c b/drivers/staging/qlge/qlge_mpi.c
> index 2630ebf50341..0f1c7da80413 100644
> --- a/drivers/staging/qlge/qlge_mpi.c
> +++ b/drivers/staging/qlge/qlge_mpi.c
> @@ -806,6 +806,7 @@ int qlge_mb_get_port_cfg(struct qlge_adapter *qdev)
>  {
>  	struct mbox_params mbc;
>  	struct mbox_params *mbcp = &mbc;
> +	u32 saved_pause_link_config = 0;

Initialization is not needed given the code below, in fact the
declaration can be moved to the block below.

>  	int status = 0;
>  
>  	memset(mbcp, 0, sizeof(struct mbox_params));
> @@ -826,7 +827,15 @@ int qlge_mb_get_port_cfg(struct qlge_adapter *qdev)
>  	} else	{
>  		netif_printk(qdev, drv, KERN_DEBUG, qdev->ndev,
>  			     "Passed Get Port Configuration.\n");
> -		qdev->link_config = mbcp->mbox_out[1];
> +		/*
> +		 * Don't let the pause parameter be overwritten by
> +		 *
> +		 * In this way, follow control can be disabled by default
> +		 * and the setting could also survive the MPI reset
> +		 */

It seems this comment is incomplete. Also, it's "flow control", not
"follow control".

> +		saved_pause_link_config = qdev->link_config & CFG_PAUSE_STD;
> +		qdev->link_config = ~CFG_PAUSE_STD & mbcp->mbox_out[1];
> +		qdev->link_config |= saved_pause_link_config;
>  		qdev->max_frame_size = mbcp->mbox_out[2];
>  	}
>  	return status;
> -- 
> 2.32.0
>