netdev - Re: [PATCH 2/2] tg3: Add code to allow ethtool to enable/disable loopback.

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Message-ID: <BANLkTikFC_Eg1PCDJiuHFsbtjmPUHRfXsA@mail.gmail.com>
Date:	Fri, 29 Apr 2011 10:45:38 -0700
From:	Mahesh Bandewar <maheshb@...gle.com>
To:	Matt Carlson <mcarlson@...adcom.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Michael Chan <mchan@...adcom.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	"Micha? Miros?aw" <mirq-linux@...e.qmqm.pl>
Subject: Re: [PATCH 2/2] tg3: Add code to allow ethtool to enable/disable loopback.

On Thu, Apr 28, 2011 at 7:46 PM, Matt Carlson <mcarlson@...adcom.com> wrote:
> On Thu, Apr 28, 2011 at 06:42:02PM -0700, Mahesh Bandewar wrote:
>> >> + ? ? spin_unlock_bh(&tp->lock);
>> >> +
>> >> + ? ? return err;
>> >> +}
>> >> +
>> >> ?static inline void tg3_set_mtu(struct net_device *dev, struct tg3 *tp,
>> >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?int new_mtu)
>> >> ?{
>> >> @@ -15028,6 +15055,7 @@ static const struct net_device_ops tg3_netdev_ops = {
>> >> ? ? ? .ndo_tx_timeout ? ? ? ? = tg3_tx_timeout,
>> >> ? ? ? .ndo_change_mtu ? ? ? ? = tg3_change_mtu,
>> >> ? ? ? .ndo_fix_features ? ? ? = tg3_fix_features,
>> >> + ? ? .ndo_set_features ? ? ? = tg3_set_features,
>> >> ?#ifdef CONFIG_NET_POLL_CONTROLLER
>> >> ? ? ? .ndo_poll_controller ? ?= tg3_poll_controller,
>> >> ?#endif
>> >> @@ -15044,6 +15072,7 @@ static const struct net_device_ops tg3_netdev_ops_dma_bug = {
>> >> ? ? ? .ndo_do_ioctl ? ? ? ? ? = tg3_ioctl,
>> >> ? ? ? .ndo_tx_timeout ? ? ? ? = tg3_tx_timeout,
>> >> ? ? ? .ndo_change_mtu ? ? ? ? = tg3_change_mtu,
>> >> + ? ? .ndo_set_features ? ? ? = tg3_set_features,
>> >> ?#ifdef CONFIG_NET_POLL_CONTROLLER
>> >> ? ? ? .ndo_poll_controller ? ?= tg3_poll_controller,
>> >> ?#endif
>> >> @@ -15241,6 +15270,9 @@ static int __devinit tg3_init_one(struct pci_dev *pdev,
>> >> ? ? ? dev->features |= hw_features;
>> >> ? ? ? dev->vlan_features |= hw_features;
>> >>
>> >> + ? ? /* Add the loopback capability */
>> >> + ? ? dev->hw_features |= NETIF_F_LOOPBACK;
>> >
>> > Not all tg3 devices can do MAC loopback. ?I'd suggest qualifying this
>> > with:
>> >
>> > ? ? ? ? ? ? ? ?if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5780 ||
>> > ? ? ? ? ? ? ? ? ? ?(tp->tg3_flags & TG3_FLAG_CPMU_PRESENT))
>> >
>> > But that will exclude a lot of our newer devices. ?Does it matter what
>> > type of loopback is used? ?Newer devices prefer internal phy loopback
>> > over MAC loopback.
>> >
>> As long as device supports some sort of loopback, we should be setting
>> this capability and move this logic (or similar) to set_features() and
>> choose the method that is supported. Since several devices support
>> loopback at various levels, to keep it consistent, we should be
>> setting the loopback closest to the host. So can I simply set the
>> int-phy loopback in the else part of the above 'provided if' or would
>> need other logic? or in other words -
>>
>>  if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5780 ||
>> (tp->tg3_flags & TG3_FLAG_CPMU_PRESENT))
>>     supported_mode = MAC;
>> else
>>     supported_mode = INTPHY;
>>
>> if (supported_mode == MAC)
>>     cur_mode = tr32(MAC_MODE);
>> else
>>     tg3_readphy(tp, MII_BMCR, &cur_mode);
>>
>> Would something like this work?
>
> That might be where we want to end up, but it'll be some work to get
> there.  Maybe it makes sense to just keep MAC loopback mode for now and
> only enable it for a subset of devices.  Adding phy loopback mode sounds
> like it will require some surgery.
>
Thanks for your comments Matt, I'll post the updated patch soon.

--mahesh..
>
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