linux-kernel - Re: [PATCH v3] PCI/AER: Use pci_clear_and_set_config

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Message-ID: <aKDpIeQgt7I9Ts8F@wunner.de>
Date: Sat, 16 Aug 2025 22:25:05 +0200
From: Lukas Wunner <lukas@...ner.de>
To: Hans Zhang <18255117159@....com>
Cc: mahesh@...ux.ibm.com, bhelgaas@...gle.com, oohall@...il.com,
	mani@...nel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] PCI/AER: Use pci_clear_and_set_config_dword() to
 simplify mask updates

On Sun, Aug 17, 2025 at 12:17:43AM +0800, Hans Zhang wrote:
> Replace manual read-modify-write sequences in multiple functions with
> pci_clear_and_set_config_dword() helper to reduce code duplication.

None of the occurrences you're replacing is clearing *and* setting
bits at the same time.  They all either clear or set bits, but not both.

For the PCIe Capability, there are pcie_capability_clear_dword()
and pcie_capability_set_dword() helpers.

It would arguably be clearer and less confusing to introduce similar
pci_clear_config_dword() and pci_set_config_dword() helpers and use
those, instead of using pci_clear_and_set_config_dword() and setting
one argument to 0.

Thanks,

Lukas

> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index e286c197d716..3d37e2b7e412 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -176,14 +176,13 @@ static int enable_ecrc_checking(struct pci_dev *dev)
>  static int disable_ecrc_checking(struct pci_dev *dev)
>  {
>  	int aer = dev->aer_cap;
> -	u32 reg32;
>  
>  	if (!aer)
>  		return -ENODEV;
>  
> -	pci_read_config_dword(dev, aer + PCI_ERR_CAP, &reg32);
> -	reg32 &= ~(PCI_ERR_CAP_ECRC_GENE | PCI_ERR_CAP_ECRC_CHKE);
> -	pci_write_config_dword(dev, aer + PCI_ERR_CAP, reg32);
> +	pci_clear_and_set_config_dword(dev, aer + PCI_ERR_CAP,
> +				       PCI_ERR_CAP_ECRC_GENE |
> +				       PCI_ERR_CAP_ECRC_CHKE, 0);
>  
>  	return 0;
>  }
> @@ -1102,15 +1101,12 @@ static bool find_source_device(struct pci_dev *parent,
>  static void pci_aer_unmask_internal_errors(struct pci_dev *dev)
>  {
>  	int aer = dev->aer_cap;
> -	u32 mask;
>  
> -	pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, &mask);
> -	mask &= ~PCI_ERR_UNC_INTN;
> -	pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, mask);
> +	pci_clear_and_set_config_dword(dev, aer + PCI_ERR_UNCOR_MASK,
> +				       PCI_ERR_UNC_INTN, 0);
>  
> -	pci_read_config_dword(dev, aer + PCI_ERR_COR_MASK, &mask);
> -	mask &= ~PCI_ERR_COR_INTERNAL;
> -	pci_write_config_dword(dev, aer + PCI_ERR_COR_MASK, mask);
> +	pci_clear_and_set_config_dword(dev, aer + PCI_ERR_COR_MASK,
> +				       PCI_ERR_COR_INTERNAL, 0);
>  }
>  
>  static bool is_cxl_mem_dev(struct pci_dev *dev)
> @@ -1556,23 +1552,19 @@ static irqreturn_t aer_irq(int irq, void *context)
>  static void aer_enable_irq(struct pci_dev *pdev)
>  {
>  	int aer = pdev->aer_cap;
> -	u32 reg32;
>  
>  	/* Enable Root Port's interrupt in response to error messages */
> -	pci_read_config_dword(pdev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
> -	reg32 |= ROOT_PORT_INTR_ON_MESG_MASK;
> -	pci_write_config_dword(pdev, aer + PCI_ERR_ROOT_COMMAND, reg32);
> +	pci_clear_and_set_config_dword(pdev, aer + PCI_ERR_ROOT_COMMAND,
> +				       0, ROOT_PORT_INTR_ON_MESG_MASK);
>  }
>  
>  static void aer_disable_irq(struct pci_dev *pdev)
>  {
>  	int aer = pdev->aer_cap;
> -	u32 reg32;
>  
>  	/* Disable Root Port's interrupt in response to error messages */
> -	pci_read_config_dword(pdev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
> -	reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
> -	pci_write_config_dword(pdev, aer + PCI_ERR_ROOT_COMMAND, reg32);
> +	pci_clear_and_set_config_dword(pdev, aer + PCI_ERR_ROOT_COMMAND,
> +				       ROOT_PORT_INTR_ON_MESG_MASK, 0);
>  }
>  
>  /**