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SubjectRe: ethtool occationally fails to communicate with with ucc_geth
On Wed, 2013-02-06 at 15:05 -0500, Lennart Sorensen wrote:
> We are occationally seeing ethtool fail to communicate with ucc_geth.
> I think I have tracked down why it happens, but I don't see a good way
> to fix it.
> When the phy state changes, adjust_link() checks if the state has changed
> and if the link is up. If it is it does:
> if (new_state) {
> /*
> * To change the MAC configuration we need to disable
> * the controller. To do so, we have to either grab
> * ugeth->lock, which is a bad idea since 'graceful
> * stop' commands might take quite a while, or we can
> * quiesce driver's activity.
> */
> ugeth_quiesce(ugeth);
> ugeth_disable(ugeth, COMM_DIR_RX_AND_TX);
> out_be32(&ug_regs->maccfg2, tempval);
> out_be32(&uf_regs->upsmr, upsmr);
> ugeth_enable(ugeth, COMM_DIR_RX_AND_TX);
> ugeth_activate(ugeth);
> }
> The problem I believe is that ugeth_quiesce() does netif_device_detach
> which clears __LINK_STATE_PRESENT, and hence makes dev_ethtool fail
> due to:
> if (!dev || !netif_device_present(dev))
> return -ENODEV;
> So if ethtool happens to be run between ugeth_quiesce() and
> ugeth_activate(), it fails as if the device simply doesn't exist, which
> is of course not true, it's just temporarily disabled.
> Any suggestions?

This seems to be a workaround for a bug in phylib: phy_state_machine()
calls netif_carrier_on() before adjust_link(), so the TX scheduler can
start immediately even though the MAC has not been configured.

A better workaround would be to use netif_carrier_{off,on}() in
ugeth_{quiesce,activate}() respectively instead of
netif_device_{detach,attach}(). But I think phylib really ought to be


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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