Re: [PATCH net-next 9/9] net: stmmac: convert to phylink managed EEE support

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Wed, Feb 26, 2025 at 10:11:58AM +0000, Jon Hunter wrote:
> 
> On 26/02/2025 10:02, Russell King (Oracle) wrote:
> > On Tue, Feb 25, 2025 at 02:21:01PM +0000, Jon Hunter wrote:
> > > Hi Russell,
> > > 
> > > On 19/02/2025 20:57, Russell King (Oracle) wrote:
> > > > So, let's try something (I haven't tested this, and its likely you
> > > > will need to work it in to your other change.)
> > > > 
> > > > Essentially, this disables the receive clock stop around the reset,
> > > > something the stmmac driver has never done in the past.
> > > > 
> > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > > > index 1cbea627b216..8e975863a2e3 100644
> > > > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > > > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > > > @@ -7926,6 +7926,8 @@ int stmmac_resume(struct device *dev)
> > > >    	rtnl_lock();
> > > >    	mutex_lock(&priv->lock);
> > > > +	phy_eee_rx_clock_stop(priv->dev->phydev, false);
> > > > +
> > > >    	stmmac_reset_queues_param(priv);
> > > >    	stmmac_free_tx_skbufs(priv);
> > > > @@ -7937,6 +7939,9 @@ int stmmac_resume(struct device *dev)
> > > >    	stmmac_restore_hw_vlan_rx_fltr(priv, ndev, priv->hw);
> > > > +	phy_eee_rx_clock_stop(priv->dev->phydev,
> > > > +			      priv->phylink_config.eee_rx_clk_stop_enable);
> > > > +
> > > >    	stmmac_enable_all_queues(priv);
> > > >    	stmmac_enable_all_dma_irq(priv);
> > > 
> > > 
> > > Sorry for the delay, I have been testing various issues recently and needed
> > > a bit more time to test this.
> > > 
> > > It turns out that what I had proposed last week does not work. I believe
> > > that with all the various debug/instrumentation I had added, I was again
> > > getting lucky. So when I tested again this week on top of vanilla v6.14-rc2,
> > > it did not work :-(
> > > 
> > > However, what you are suggesting above, all by itself, is working. I have
> > > tested this on top of vanilla v6.14-rc2 and v6.14-rc4 and it is working
> > > reliably. I have also tested on some other boards that use the same stmmac
> > > driver (but use the Aquantia PHY) and I have not seen any issues. So this
> > > does fix the issue I am seeing.
> > > 
> > > I know we are getting quite late in the rc for v6.14, but not sure if we
> > > could add this as a fix?
> > 
> > The patch above was something of a hack, bypassing the layering, so I
> > would like to consider how this should be done properly.
> > 
> > I'm still wondering whether the early call to phylink_resume() is
> > symptomatic of this same issue, or whether there is a PHY that needs
> > phy_start() to be called to output its clock even with link down that
> > we don't know about.
> > 
> > The phylink_resume() call is relevant to this because I'd like to put:
> > 
> > 	phy_eee_rx_clock_stop(priv->dev->phydev,
> > 			      priv->phylink_config.eee_rx_clk_stop_enable);
> > 
> > in there to ensure that the PHY is correctly configured for clock-stop,
> > but given stmmac's placement that wouldn't work.
> > 
> > I'm then thinking of phylink_pre_resume() to disable the EEE clock-stop
> > at the PHY.
> > 
> > I think the only thing we could do is try solving this problem as per
> > above and see what the fall-out from it is. I don't get the impression
> > that stmmac users are particularly active at testing patches though, so
> > it may take months to get breakage reports.
> 
> 
> We can ask Furong to test as he seems to active and making changes, but
> otherwise I am not sure how well it is being tested across various devices.
> On the other hand, it feels like there are still lingering issues like this
> with the driver and so I would hope this is moving in the right direction.
> 
> Let me know if you have a patch you want me to test and I will run in on our
> Tegra186, Tegra194 and Tegra234 devices that all use this.

Do we think this needs to be a patch for the net tree or the net-next
tree? I think we've established that it's been a long-standing bug,
so maybe if we target net-next to give it more time to be tested?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!