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

[Coiby Xu]

On Tue, Jun 22, 2021 at 04:49:51PM +0900, Benjamin Poirier wrote:
> 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 <coiby.xu@xxxxxxxxx>
> > ---
> >  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, 

Thanks for the spotting this issue!

> in fact the
> declaration can be moved to the block below.

I thought I need to put the declaration in the beginning of the
function. But it seems Linux kernel coding style doesn't require it.
I'll move it to the else block below then.

> >  	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".

Ah, yes. I should state it as "Don't let the pause parameter be 
overwritten by be overwritten by the firmware.". And thanks for
correcting the typo.
> > +		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

--
Best regards,
Coiby