linux-kernel - 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 23:17:56 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
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()

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.

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
> 

-- 
With Best Regards,
Andy Shevchenko