Message-ID: <63f9d470-e4e4-4e06-a057-1e1ab0aca9d0@nvidia.com>
Date: Wed, 26 Feb 2025 15:55:47 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Andrew Lunn <andrew+netdev@...n.ch>,
 Bryan Whitehead <bryan.whitehead@...rochip.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, linux-arm-kernel@...ts.infradead.org,
 linux-stm32@...md-mailman.stormreply.com,
 Marcin Wojtas <marcin.s.wojtas@...il.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>, netdev@...r.kernel.org,
 Paolo Abeni <pabeni@...hat.com>, UNGLinuxDriver@...rochip.com,
 "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH net-next 9/9] net: stmmac: convert to phylink managed EEE
 support


On 26/02/2025 10:59, Russell King (Oracle) wrote:
> 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?
> 

Yes I agree there is a long-standing issue here. What is unfortunate for 
Linux v6.14 is that failure rate is much higher. However, I don't see 
what I can really do about that. I can mark suspend as broken for Linux 
v6.14 for this device and then hopefully we will get this resolved 
properly.

Thanks!
Jon

-- 
nvpublic

Powered by blists - more mailing lists