linux-kernel - Re: [PATCH 2/6] MIPS: OCTEON: Remove redundant clearing of AER status registers

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Date:   Tue, 19 Oct 2021 17:53:51 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Naveen Naidu <naveennaidu479@...il.com>
Cc:     bhelgaas@...gle.com, tsbogend@...ha.franken.de,
        linux-pci@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH 2/6] MIPS: OCTEON: Remove redundant clearing of AER
 status registers

On Mon, Oct 04, 2021 at 11:29:28PM +0530, Naveen Naidu wrote:
> e8635b484f64 ("MIPS: Add Cavium OCTEON PCI support.") added MIPS
> specific code to enable PCIe and AER error reporting (*irrespective
> of CONFIG_PCIEAER value*) because PCI core didn't do that at the time.
> 
> Currently when CONFIG_PCIEAER=y, the Uncorrectable Error status,
> Correctable Error status and Root status registers are cleared
> during the PCI Bus enumeration path by pci_aer_init() via
> pci_init_capabilities()

So the current tree (before this patch) always clears these AER status
registers regardless of CONFIG_PCIEAER.

After this patch, we would clear them only if CONFIG_PCIEAER=y.  I
don't see anything in arch/mips that sets CONFIG_PCIEAER, so I'm
concerned we will no longer clear the AER status bits.

I only want to propose a change here if we're very confident that it
won't change any OCTEON behavior.

> It is now no longer necessary for Octeon code to clear AER status
> registers since it's done by PCI core.
> 
> Signed-off-by: Naveen Naidu <naveennaidu479@...il.com>
> ---
>  arch/mips/pci/pci-octeon.c | 11 -----------
>  1 file changed, 11 deletions(-)
> 
> diff --git a/arch/mips/pci/pci-octeon.c b/arch/mips/pci/pci-octeon.c
> index fc29b85cfa92..8e8b282226cc 100644
> --- a/arch/mips/pci/pci-octeon.c
> +++ b/arch/mips/pci/pci-octeon.c
> @@ -124,11 +124,6 @@ int pcibios_plat_dev_init(struct pci_dev *dev)
>  	/* Find the Advanced Error Reporting capability */
>  	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
>  	if (pos) {
> -		/* Clear Uncorrectable Error Status */
> -		pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS,
> -				      &dconfig);
> -		pci_write_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS,
> -				       dconfig);
>  		/* Enable reporting of all uncorrectable errors */
>  		/* Uncorrectable Error Mask - turned on bits disable errors */
>  		pci_write_config_dword(dev, pos + PCI_ERR_UNCOR_MASK, 0);
> @@ -138,9 +133,6 @@ int pcibios_plat_dev_init(struct pci_dev *dev)
>  		 * correctable, not if the error is reported.
>  		 */
>  		/* PCI_ERR_UNCOR_SEVER - Uncorrectable Error Severity */
> -		/* Clear Correctable Error Status */
> -		pci_read_config_dword(dev, pos + PCI_ERR_COR_STATUS, &dconfig);
> -		pci_write_config_dword(dev, pos + PCI_ERR_COR_STATUS, dconfig);
>  		/* Enable reporting of all correctable errors */
>  		/* Correctable Error Mask - turned on bits disable errors */
>  		pci_write_config_dword(dev, pos + PCI_ERR_COR_MASK, 0);
> @@ -159,9 +151,6 @@ int pcibios_plat_dev_init(struct pci_dev *dev)
>  				       PCI_ERR_ROOT_CMD_COR_EN |
>  				       PCI_ERR_ROOT_CMD_NONFATAL_EN |
>  				       PCI_ERR_ROOT_CMD_FATAL_EN);
> -		/* Clear the Root status register */
> -		pci_read_config_dword(dev, pos + PCI_ERR_ROOT_STATUS, &dconfig);
> -		pci_write_config_dword(dev, pos + PCI_ERR_ROOT_STATUS, dconfig);
>  	}
>  
>  	return 0;
> -- 
> 2.25.1
> 
> _______________________________________________
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> Linux-kernel-mentees@...ts.linuxfoundation.org
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