linux-kernel - Re: [PATCH] pci: tegra194: Fix debugfs cleanup for !CONFIG

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Message-ID: <20250405152818.GA107831@bhelgaas>
Date: Sat, 5 Apr 2025 10:28:18 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Hans Zhang <18255117159@....com>
Cc: lpieralisi@...nel.org, manivannan.sadhasivam@...aro.org,
	thierry.reding@...il.com, kw@...ux.com, robh@...nel.org,
	bhelgaas@...gle.com, jonathanh@...dia.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-tegra@...r.kernel.org
Subject: Re: [PATCH] pci: tegra194: Fix debugfs cleanup for !CONFIG_PCIEASPM

Follow subject line capitalization convention.

On Sat, Apr 05, 2025 at 10:54:59PM +0800, Hans Zhang wrote:
> When CONFIG_PCIEASPM is disabled, debugfs entries are not created, but
> tegra_pcie_dw_remove() and tegra_pcie_dw_shutdown() unconditionally call
> debugfs_remove_recursive(), leading to potential NULL pointer operations.
> 
> Introduce deinit_debugfs() to wrap debugfs_remove_recursive(), which is
> stubbed for !CONFIG_PCIEASPM. Use this function during removal/shutdown to
> ensure debugfs cleanup only occurs when entries were initialized.
> 
> This prevents kernel warnings and instability when ASPM support is
> disabled.

This looks like there should be a Fixes: tag to connect this to the
commit that introduced the problem.

If this is something that broke with the v6.15 merge window, we should
include this in v6.15 via pci/for-linus.  If this broke earlier, we
would have to decide whether pci/for-linus is still appropriate or a
stable tag.

We did merge some debugfs things for v6.15, but I don't see anything
specific to pcie-tegra194.c, so I'm confused about why this fix would
be in pcie-tegra194.c instead of some more generic place.

> Signed-off-by: Hans Zhang <18255117159@....com>
> ---
>  drivers/pci/controller/dwc/pcie-tegra194.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
> index 5103995cd6c7..d762e733c2d8 100644
> --- a/drivers/pci/controller/dwc/pcie-tegra194.c
> +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
> @@ -716,11 +716,20 @@ static void init_debugfs(struct tegra_pcie_dw *pcie)
>  	debugfs_create_devm_seqfile(pcie->dev, "aspm_state_cnt", pcie->debugfs,
>  				    aspm_state_cnt);
>  }
> +
> +static void deinit_debugfs(struct tegra_pcie_dw *pcie)
> +{
> +	if (!pcie->debugfs)
> +		return;
> +
> +	debugfs_remove_recursive(pcie->debugfs);
> +}
>  #else
>  static inline void disable_aspm_l12(struct tegra_pcie_dw *pcie) { return; }
>  static inline void disable_aspm_l11(struct tegra_pcie_dw *pcie) { return; }
>  static inline void init_host_aspm(struct tegra_pcie_dw *pcie) { return; }
>  static inline void init_debugfs(struct tegra_pcie_dw *pcie) { return; }
> +static inline void deinit_debugfs(struct tegra_pcie_dw *pcie) { return; }
>  #endif
>  
>  static void tegra_pcie_enable_system_interrupts(struct dw_pcie_rp *pp)
> @@ -2289,7 +2298,7 @@ static void tegra_pcie_dw_remove(struct platform_device *pdev)
>  		if (!pcie->link_state)
>  			return;
>  
> -		debugfs_remove_recursive(pcie->debugfs);
> +		deinit_debugfs(pcie->debugfs);
>  		tegra_pcie_deinit_controller(pcie);
>  		pm_runtime_put_sync(pcie->dev);
>  	} else {
> @@ -2408,7 +2417,7 @@ static void tegra_pcie_dw_shutdown(struct platform_device *pdev)
>  		if (!pcie->link_state)
>  			return;
>  
> -		debugfs_remove_recursive(pcie->debugfs);
> +		deinit_debugfs(pcie->debugfs);
>  		tegra_pcie_downstream_dev_to_D0(pcie);
>  
>  		disable_irq(pcie->pci.pp.irq);
> 
> base-commit: a8662bcd2ff152bfbc751cab20f33053d74d0963
> -- 
> 2.25.1
>