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

[Jon Hunter <jonathanh@nvidia.com>]

On 26/02/2025 16:00, Russell King (Oracle) wrote:
> On Wed, Feb 26, 2025 at 03:55:47PM +0000, Jon Hunter wrote:
>>
>> 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.
> 
> If we put the patches in net-next, it can have longer to be tested - it
> won't go straight into 6.14, but will wait until after net-next gets
> merged, and it'll then be backported to 6.14 stable trees.

Yes that would be great.

> I think the fix that I've outlined is too big and too risky to go
> straight into 6.14, but the smaller fix may be better, but would then
> need to be rewritten into the larger fix.

I think it is fine and better to get it fixed for the long term.

Thanks
Jon

-- 
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