netdev - Re: [PATCH RFC v1 7/7] net: cpsw: resume/suspend PHY on port start/stop

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Date:	Wed, 20 Nov 2013 21:57:08 +0100
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Florian Fainelli <f.fainelli@...il.com>
CC:	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v1 7/7] net: cpsw: resume/suspend PHY on port start/stop

On 11/20/2013 09:48 PM, Florian Fainelli wrote:
> 2013/11/20 Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>:
>> Network PHYs consume a noticable amount of power. This adds phy_resume
>> on slave_open and phy_suspend on slave_stop to save this power if the
>> port is down anyway.
>>
>> Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
>> ---
>> Cc: David S. Miller <davem@...emloft.net>
>> Cc: netdev@...r.kernel.org
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>> ---
>>   drivers/net/ethernet/ti/cpsw.c |    2 ++
>>   1 files changed, 2 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
>> index 90d41d2..f1dc54f 100644
>> --- a/drivers/net/ethernet/ti/cpsw.c
>> +++ b/drivers/net/ethernet/ti/cpsw.c
>> @@ -1013,6 +1013,7 @@ static void cpsw_slave_open(struct cpsw_slave *slave, struct cpsw_priv *priv)
>>          } else {
>>                  dev_info(priv->dev, "phy found : id is : 0x%x\n",
>>                           slave->phy->phy_id);
>> +               phy_resume(slave->phy);
>>                  phy_start(slave->phy);
>
> Cannot phy_start() figure this out for us based on the internal PHY
> device state machine?

Yeah, as I said in the cover letter, I started with mv643xx_eth which
is not using phy_start/stop as it probably should be. As soon as I
looked at mvneta/cpsw, I also came to the conclusion that
phy_suspend/resume should be hidden in phy_start/stop.

> I would imagine that you would want to call phy_suspend/resume from an
> Ethernet driver's PM suspend/resume callbacks to make sure that the
> PHY also enters a low power mode, but I do not want to have to
> remember that I need to call phy_resume before phy_start for instance.
> As of today we have PHY_HALTED/PHY_RESUMING, and I think we certainly
> need at least a PHY_SUSPENDED state to help us with that.
>
>>
>>                  /* Configure GMII_SEL register */
>> @@ -1081,6 +1082,7 @@ static void cpsw_slave_stop(struct cpsw_slave *slave, struct cpsw_priv *priv)
>>          if (!slave->phy)
>>                  return;
>>          phy_stop(slave->phy);
>> +       phy_suspend(slave->phy);
>
> Same here, why is not that hidden in phy_stop? If there is any fear
> that this breaks setups where WoL is used or such, we could add a new
> argument to phy_connect() and friends which says whether it is okay to
> auto-suspend the PHY upon PHY_stop
>
>>          phy_disconnect(slave->phy);
>>          slave->phy = NULL;
>>   }
>> --
>> 1.7.2.5
>>
>> --
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>
>
>

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