netdev - Re: [PATCH v3 1/1 net-next] net: fec: enable pause frame to improve rx prefomance for 1G network

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Date:	Fri, 25 Jan 2013 09:50:24 +0800
From:	Frank Li <lznuaa@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Frank Li <Frank.Li@...escale.com>, shawn.guo@...aro.org,
	B38611@...escale.com, davem@...emloft.net,
	linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
	s.hauer@...gutronix.de
Subject: Re: [PATCH v3 1/1 net-next] net: fec: enable pause frame to improve
 rx prefomance for 1G network

2013/1/25 Ben Hutchings <bhutchings@...arflare.com>:
> On Thu, 2013-01-24 at 10:16 +0800, Frank Li wrote:
>> 2013/1/24 Ben Hutchings <bhutchings@...arflare.com>:
>> > On Thu, 2013-01-17 at 10:55 +0800, Frank Li wrote:
>> >> The limition of imx6 internal bus cause fec can't achieve 1G perfomance.
>> >> There will be many packages lost because FIFO over run.
>> >>
>> >> This patch enable pause frame flow control.
>> > [...]
>> >> --- a/drivers/net/ethernet/freescale/fec.c
>> >> +++ b/drivers/net/ethernet/freescale/fec.c
>> > [...]
>> >> +static int fec_enet_set_pauseparam(struct net_device *ndev,
>> >> +                                struct ethtool_pauseparam *pause)
>> >> +{
>> >> +     struct fec_enet_private *fep = netdev_priv(ndev);
>> >> +
>> >> +     if (pause->tx_pause != pause->rx_pause) {
>> >> +             netdev_info(ndev,
>> >> +                     "hardware only support enable/disable both tx and rx");
>> >> +             return -EINVAL;
>> >> +     }
>> >> +
>> >> +     fep->pause_flag = 0;
>> >> +
>> >> +     /* tx pause must be same as rx pause */
>> >> +     fep->pause_flag |= pause->rx_pause ? FEC_PAUSE_FLAG_ENABLE : 0;
>> >> +     fep->pause_flag |= pause->autoneg ? FEC_PAUSE_FLAG_AUTONEG : 0;
>> >> +
>> >> +     if (pause->rx_pause || pause->autoneg) {
>> >> +             fep->phy_dev->supported |= ADVERTISED_Pause;
>> >> +             fep->phy_dev->advertising |= ADVERTISED_Pause;
>> >> +     } else {
>> >> +             fep->phy_dev->supported &= ~ADVERTISED_Pause;
>> >> +             fep->phy_dev->advertising &= ~ADVERTISED_Pause;
>> >> +     }
>> > [...]
>> >
>> > Why is this changing the supported flags, i.e. device capabilities?  You
>> > need to leave those flags alone and reject an attempt to enable pause
>> > frames on a device that doesn't support them.
>>
>> I go through phylib, I have not found good place set ADVERTISED_Pause
>> capabilities.
>> genphy_config_init never check Pause capabilities.
>
> I agree that phylib can't initialise pause capabilities because those
> depend on the MAC.  But look at which function I'm quoting: this is the
> ethtool operation, which shouldn't change capabilities.

Where is good place do you think? in probe function?

>
> Ben.
>
> --
> Ben Hutchings, Staff Engineer, Solarflare
> Not speaking for my employer; that's the marketing department's job.
> They asked us to note that Solarflare product names are trademarked.
>
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