RE: [PATCH v2 04/10] net/gve: add link update support

["Guo, Junfeng" <junfeng.guo@intel.com>]

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@xilinx.com>
> Sent: Friday, September 2, 2022 01:23
> To: Guo, Junfeng <junfeng.guo@intel.com>; Zhang, Qi Z
> <qi.z.zhang@intel.com>; Wu, Jingjing <jingjing.wu@intel.com>
> Cc: dev@dpdk.org; Li, Xiaoyun <xiaoyun.li@intel.com>;
> awogbemila@google.com; Richardson, Bruce
> <bruce.richardson@intel.com>
> Subject: Re: [PATCH v2 04/10] net/gve: add link update support
> 
> On 8/29/2022 9:41 AM, Junfeng Guo wrote:
> 
> >
> > Support dev_ops link_update.
> >
> > Signed-off-by: Xiaoyun Li <xiaoyun.li@intel.com>
> > Signed-off-by: Junfeng Guo <junfeng.guo@intel.com>
> > ---
> >   drivers/net/gve/gve_ethdev.c | 30
> ++++++++++++++++++++++++++++++
> >   1 file changed, 30 insertions(+)
> >
> > diff --git a/drivers/net/gve/gve_ethdev.c
> b/drivers/net/gve/gve_ethdev.c
> > index f10f273f7d..435115c047 100644
> > --- a/drivers/net/gve/gve_ethdev.c
> > +++ b/drivers/net/gve/gve_ethdev.c
> > @@ -37,10 +37,39 @@ gve_dev_configure(__rte_unused struct
> rte_eth_dev *dev)
> >          return 0;
> >   }
> >
> > +static int
> > +gve_link_update(struct rte_eth_dev *dev, __rte_unused int
> wait_to_complete)
> > +{
> > +       struct gve_priv *priv = dev->data->dev_private;
> > +       struct rte_eth_link link;
> > +       int err;
> > +
> > +       memset(&link, 0, sizeof(link));
> > +       link.link_duplex = RTE_ETH_LINK_FULL_DUPLEX;
> > +       link.link_autoneg = RTE_ETH_LINK_AUTONEG;
> > +
> > +       if (!dev->data->dev_started) {
> > +               link.link_status = RTE_ETH_LINK_DOWN;
> > +               link.link_speed = RTE_ETH_SPEED_NUM_NONE;
> > +       } else {
> > +               link.link_status = RTE_ETH_LINK_UP;
> > +               PMD_INIT_LOG(DEBUG, "Get link status from hw");
> > +               err = gve_adminq_report_link_speed(priv);
> 
> As far as I can see the API is calling an adminq command, is this
> command blocking until link is up? If so is there a non blocking version
> to utilize 'wait_to_complete', instead of ignoring it?

Yes, getting the link speed via an adminq command here is an blocking
until, and that's the only method we can utilize. As for the non-blocking
version, it depends on the real behavior of the HW (or backend), which 
is like a black-box to us. There is no HW register to store the link status
info. Seems the 'wait_to_complete' cannot be used here. Thanks!

> 
> Also what will happen if 'start()' dev_ops called but cable is not
> plugged in at all, won't this set link status still to "UP"?

Yes, that could be a terrible situation. Since this driver is running on the
cloud environment, we can only assume that the HW & backend part
work well when we run our driver. Thanks!

>