Date:   Thu, 12 Jan 2017 11:34:47 -0600
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
CC:     <mugunthanvnm@...com>, <linux-omap@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH 3/4] net: ethernet: ti: cpsw: don't duplicate ndev_running



On 01/10/2017 07:56 PM, Ivan Khoronzhuk wrote:
> 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_get_usage_count () sounds good

> 
>>
>>
>>>  		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.

yes. please. comments are required at least.

its actually a question why __LINK_STATE_START is managed this way in ./net/core/dev.c

__dev_open()
	set_bit(__LINK_STATE_START, &dev->state); <---- before .ndo_open()

	if (!ret && ops->ndo_open)
		ret = ops->ndo_open(dev);

	<---- shouldn't set_bit(__LINK_STATE_START, &dev->state) be after calling .ndo_open() ??

__dev_close_many()

	clear_bit(__LINK_STATE_START, &dev->state); <-stop sequence is differ from open.

	if (ops->ndo_stop)
			ops->ndo_stop(dev);


-- 
regards,
-grygorii

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