netdev - Re: [PATCH 1/2] stmmac: intel: Add a missing clk_disable_unprepare() call in intel_eth_pci

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Date:   Sat, 30 Jul 2022 22:30:36 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     vee.khee.wong@...el.com, weifeng.voon@...el.com,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Joakim Zhang <qiangqing.zhang@....com>,
        Andrew Lunn <andrew@...n.ch>, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org, netdev@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] stmmac: intel: Add a missing clk_disable_unprepare()
 call in intel_eth_pci_remove()

Le 30/07/2022 à 22:17, Andy Shevchenko a écrit :
> On Sat, Jul 30, 2022 at 08:19:47PM +0200, Christophe JAILLET wrote:
>> Commit 09f012e64e4b ("stmmac: intel: Fix clock handling on error and remove
>> paths") removed this clk_disable_unprepare()
>>
>> This was partly revert by commit ac322f86b56c ("net: stmmac: Fix clock
>> handling on remove path") which removed this clk_disable_unprepare()
>> because:
>> "
>>     While unloading the dwmac-intel driver, clk_disable_unprepare() is
>>     being called twice in stmmac_dvr_remove() and
>>     intel_eth_pci_remove(). This causes kernel panic on the second call.
>> "
>>
>> However later on, commit 5ec55823438e8 ("net: stmmac: add clocks management
>> for gmac driver") has updated stmmac_dvr_remove() which do not call
>> clk_disable_unprepare() anymore.
>>
>> So this call should now be called from intel_eth_pci_remove().
> 
> The correct way of fixing it (which might be very well end up functionally
> the same as this patch), is to introduce ->quit() in struct stmmac_pci_info
> and assign it correctly, because not all platforms enable clocks.

I won't be able to propose anything like that.

By the way, in the first sentence of my log, s/removed/added/.
(I hope that it can be fixed when/if the patch is applied)


Thanks for the review.

CJ

> 
> Perhaps, we may leave this patch as is (for the sake of easy backporting) and
> apply another one as I explained above to avoid similar mistakes in the future.
> 
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> 
>> Fixes: 5ec55823438e8 ("net: stmmac: add clocks management for gmac driver")
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
>> ---
>> /!\     This patch is HIGHLY speculative.     /!\
>>
>> The corresponding clk_disable_unprepare() is still called within the pm
>> related stmmac_bus_clks_config() function.
>>
>> However, with my limited understanding of the pm API, I think it that the
>> patch is valid.
>> (in other word, does the pm_runtime_put() and/or pm_runtime_disable()
>> and/or stmmac_dvr_remove() can end up calling .runtime_suspend())
>>
>> So please review with care, as I'm not able to test the change by myself.
>>
>>
>> If I'm wrong, maybe a comment explaining why it is safe to have this
>> call in the error handling path of the probe and not in the remove function
>> would avoid erroneous patches generated from static code analyzer to be
>> sent.
>> ---
>>   drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
>> index 52f9ed8db9c9..9f38642f86ce 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
>> @@ -1134,6 +1134,7 @@ static void intel_eth_pci_remove(struct pci_dev *pdev)
>>   
>>   	stmmac_dvr_remove(&pdev->dev);
>>   
>> +	clk_disable_unprepare(plat->stmmac_clk);
>>   	clk_unregister_fixed_rate(priv->plat->stmmac_clk);
>>   
>>   	pcim_iounmap_regions(pdev, BIT(0));
>> -- 
>> 2.34.1
>>
>