linux-kernel - Re: [PATCH 3/4] net: ethernet: ti: cpsw: don't duplicate ndev

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Date:   Wed, 11 Jan 2017 03:56:20 +0200
From:   Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     netdev@...r.kernel.org, mugunthanvnm@...com,
        linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] net: ethernet: ti: cpsw: don't duplicate ndev_running

On Mon, Jan 09, 2017 at 11:25:38AM -0600, Grygorii Strashko wrote:
> 
> 
> On 01/08/2017 10:41 AM, Ivan Khoronzhuk wrote:
> > No need to create additional vars to identify if interface is running.
> > So simplify code by removing redundant var and checking usage counter
> > instead.
> > 
> > Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
> > ---
> >  drivers/net/ethernet/ti/cpsw.c | 14 ++++----------
> >  1 file changed, 4 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
> > index 40d7fc9..daae87f 100644
> > --- a/drivers/net/ethernet/ti/cpsw.c
> > +++ b/drivers/net/ethernet/ti/cpsw.c
> > @@ -357,7 +357,6 @@ struct cpsw_slave {
> >  	struct phy_device		*phy;
> >  	struct net_device		*ndev;
> >  	u32				port_vlan;
> > -	u32				open_stat;
> >  };
> >  
> >  static inline u32 slave_read(struct cpsw_slave *slave, u32 offset)
> > @@ -1241,7 +1240,7 @@ static int cpsw_common_res_usage_state(struct cpsw_common *cpsw)
> >  	u32 usage_count = 0;
> >  
> >  	for (i = 0; i < cpsw->data.slaves; i++)
> > -		if (cpsw->slaves[i].open_stat)
> > +		if (netif_running(cpsw->slaves[i].ndev))
> >  			usage_count++;
> 
> Not sure this will work as you expected, but may be I've missed smth :(
I've changed conditions, will work.

> 
> code in static int __dev_open(struct net_device *dev)
> ..
> 	set_bit(__LINK_STATE_START, &dev->state);
> 
> 	if (ops->ndo_validate_addr)
> 		ret = ops->ndo_validate_addr(dev);
> 
> 	if (!ret && ops->ndo_open)
> 		ret = ops->ndo_open(dev);
> 
> 	netpoll_poll_enable(dev);
> 
> 	if (ret)
> 		clear_bit(__LINK_STATE_START, &dev->state);
> ..
> 
> so, netif_running(ndev) will start returning true before calling ops->ndo_open(dev);
Yes, It's done bearing it in mind of course.

> 
> >  
> >  	return usage_count;
> > @@ -1502,7 +1501,7 @@ static int cpsw_ndo_open(struct net_device *ndev)
> >  		 CPSW_RTL_VERSION(reg));
> >  
> >  	/* initialize host and slave ports */
> > -	if (!cpsw_common_res_usage_state(cpsw))
> > +	if (cpsw_common_res_usage_state(cpsw) < 2)
> 
> Ah. You've changed the condition here.
> 
> I think it might be reasonable to hide this inside cpsw_common_res_usage_state()
> and seems it can be renamed to smth like cpsw_is_running().
It probably needs to be renamed to smth a little different,
like cpsw_get_usage_count ...or cpsw_get_open_ndev_count

> 
> 
> >  		cpsw_init_host_port(priv);
> >  	for_each_slave(priv, cpsw_slave_open, priv);
> >  
> > @@ -1513,7 +1512,7 @@ static int cpsw_ndo_open(struct net_device *ndev)
> >  		cpsw_ale_add_vlan(cpsw->ale, cpsw->data.default_vlan,
> >  				  ALE_ALL_PORTS, ALE_ALL_PORTS, 0, 0);
> >  
> > -	if (!cpsw_common_res_usage_state(cpsw)) {
> > +	if (cpsw_common_res_usage_state(cpsw) < 2) {
> >  		/* disable priority elevation */
> >  		__raw_writel(0, &cpsw->regs->ptype);
> >  
> > @@ -1556,9 +1555,6 @@ static int cpsw_ndo_open(struct net_device *ndev)
> >  	cpdma_ctlr_start(cpsw->dma);
> >  	cpsw_intr_enable(cpsw);
> >  
> > -	if (cpsw->data.dual_emac)
> > -		cpsw->slaves[priv->emac_port].open_stat = true;
> > -
> >  	return 0;
> >  
> >  err_cleanup:
> > @@ -1578,7 +1574,7 @@ static int cpsw_ndo_stop(struct net_device *ndev)
> >  	netif_tx_stop_all_queues(priv->ndev);
> >  	netif_carrier_off(priv->ndev);
> >  
> > -	if (cpsw_common_res_usage_state(cpsw) <= 1) {
> > +	if (!cpsw_common_res_usage_state(cpsw)) {
> 
> and here __LINK_STATE_START will be cleared before calling ops->ndo_stop(dev);
Actually it's changed because of it.

> So, from one side netif_running(ndev) usage will simplify cpsw_common_res_usage_state() internals,
> but from another side - it will make places where it's used even more entangled :( as for me,
> because when cpsw_common_res_usage_state() will return 1 in cpsw_ndo_open() it will mean
> "no interfaces is really running yet", but the same value 1 in cpsw_ndo_stop()
why not? no interfaces running, except the one excuting ndo_open now.
It's more clear then duplicating it and using two different ways in
different places for identifing running devices. Current way more
close to some testing code, not final version. Just to be consistent
better to change it.

Yes, it returns different results when it's called from ndo_close and
ndo_open. Maybe name for the function is not very close to an action
it's doing, it declares more intention, and even not for every case.
What about to rename it to some cpsw_get_open_ndev_count and add
comments in several places explaining what it actually do.

> will mean "there are still one is running".
> 
> >  		napi_disable(&cpsw->napi_rx);
> >  		napi_disable(&cpsw->napi_tx);
> >  		cpts_unregister(cpsw->cpts);
> > @@ -1592,8 +1588,6 @@ static int cpsw_ndo_stop(struct net_device *ndev)
> >  		cpsw_split_res(ndev);
> >  
> >  	pm_runtime_put_sync(cpsw->dev);
> > -	if (cpsw->data.dual_emac)
> > -		cpsw->slaves[priv->emac_port].open_stat = false;
> >  	return 0;
> >  }
> >  
> > 
> 
> -- 
> regards,
> -grygorii