linux-kernel - Re: [PATCH v3] pci: controller: pci-ftpci100: Release the clock resources

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Message-ID: <430d0357-d10e-db3d-bc82-722b022b519b@wanadoo.fr>
Date:   Mon, 8 May 2023 08:59:15 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Junyan Ye <yejunyan@...t.edu.cn>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Murray <amurray@...goodpenguin.co.uk>
Cc:     hust-os-kernel-patches@...glegroups.com,
        Dongliang Mu <dzm91@...t.edu.cn>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] pci: controller: pci-ftpci100: Release the clock
 resources

Le 08/05/2023 à 06:36, Junyan Ye a écrit :
> Smatch reported:
> 1. drivers/pci/controller/pci-ftpci100.c:526 faraday_pci_probe() warn:
> 'clk' from clk_prepare_enable() not released on lines: 442,451,462,478,512,517.
> 2. drivers/pci/controller/pci-ftpci100.c:526 faraday_pci_probe() warn:
> 'p->bus_clk' from clk_prepare_enable() not released on lines: 451,462,478,512,517.
> 
> The clock resource is obtained by devm_clk_get(), and then
> clk_prepare_enable() makes the clock resource ready for use. After that,
> clk_disable_unprepare() should be called to release the clock resource
> when it is no longer needed. However, while doing some error handling
> in faraday_pci_probe(), clk_disable_unprepare() is not called to release
> clk and p->bus_clk before returning. These return lines are exactly 442,
> 451, 462, 478, 512, 517.
> 
> Fix this warning by replacing devm_clk_get() with devm_clk_get_enabled(),
> which is equivalent to devm_clk_get() + clk_prepare_enable(). And with
> devm_clk_get_enabled(), the clock will automatically be disabled,
> unprepared and freed when the device is unbound from the bus.
> 
> Fixes: b3c433efb8a3 ("PCI: faraday: Fix wrong pointer passed to PTR_ERR()")
> Fixes: 2eeb02b28579 ("PCI: faraday: Add clock handling")
> Fixes: 783a862563f7 ("PCI: faraday: Use pci_parse_request_of_pci_ranges()")
> Fixes: d3c68e0a7e34 ("PCI: faraday: Add Faraday Technology FTPCI100 PCI Host Bridge driver")
> Fixes: f1e8bd21e39e ("PCI: faraday: Convert IRQ masking to raw PCI config accessors")
> Reviewed-by: Dongliang Mu <dzm91@...t.edu.cn>
> Signed-off-by: Junyan Ye <yejunyan@...t.edu.cn>
> ---
> v2 -> v3: Rebase to v6.4-rc1 and modify commit message.
> v1 -> v2: Switch from clk_disable_unprepare() to devm_clk_get_enabled() to release the clock.
> This issue is found by static analyzer.
> 
>   drivers/pci/controller/pci-ftpci100.c | 14 ++------------
>   1 file changed, 2 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-ftpci100.c b/drivers/pci/controller/pci-ftpci100.c
> index ecd3009df586..6e7981d2ed5e 100644
> --- a/drivers/pci/controller/pci-ftpci100.c
> +++ b/drivers/pci/controller/pci-ftpci100.c
> @@ -429,22 +429,12 @@ static int faraday_pci_probe(struct platform_device *pdev)
>   	p->dev = dev;
>   
>   	/* Retrieve and enable optional clocks */

Hi,

completely unrelated to your patch, but this comments state "optional". 
The code below seems to make both clocks mandatory.

Moreover, a few lines later, we have:
     if (!IS_ERR(p->bus_clk)) {
which seems to say that bus_clk is optional.

This was introduced by 2eeb02b28579.

Just a guess, but either the comment should be updated, or the code 
modified.

Just my 2c,

CJ


> -	clk = devm_clk_get(dev, "PCLK");
> +	clk = devm_clk_get_enabled(dev, "PCLK");
>   	if (IS_ERR(clk))
>   		return PTR_ERR(clk);
> -	ret = clk_prepare_enable(clk);
> -	if (ret) {
> -		dev_err(dev, "could not prepare PCLK\n");
> -		return ret;
> -	}
> -	p->bus_clk = devm_clk_get(dev, "PCICLK");
> +	p->bus_clk = devm_clk_get_enabled(dev, "PCICLK");
>   	if (IS_ERR(p->bus_clk))
>   		return PTR_ERR(p->bus_clk);
> -	ret = clk_prepare_enable(p->bus_clk);
> -	if (ret) {
> -		dev_err(dev, "could not prepare PCICLK\n");
> -		return ret;
> -	}
>   
>   	p->base = devm_platform_ioremap_resource(pdev, 0);
>   	if (IS_ERR(p->base))