linux-kernel - Re: [PATCH 3/3] PCI/AER: Use pci_aer_raw_clear_status() to clear root port's AER error status

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Date:   Thu, 22 Sep 2022 16:50:30 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Zhuo Chen <chenzhuo.1@...edance.com>
Cc:     fancer.lancer@...il.com, jdmason@...zu.us, dave.jiang@...el.com,
        allenbh@...il.com, bhelgaas@...gle.com, ruscur@...sell.cc,
        oohall@...il.com, james.smart@...adcom.com,
        dick.kennedy@...adcom.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        ntb@...ts.linux.dev, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 3/3] PCI/AER: Use pci_aer_raw_clear_status() to clear
 root port's AER error status

On Fri, Sep 02, 2022 at 02:16:34AM +0800, Zhuo Chen wrote:
> Statements clearing AER error status in aer_enable_rootport() has the
> same function as pci_aer_raw_clear_status(). So we replace them, which
> has no functional changes.
> 
> Signed-off-by: Zhuo Chen <chenzhuo.1@...edance.com>
> ---
>  drivers/pci/pcie/aer.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index d2996afa80f6..eb0193f279f2 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -1287,12 +1287,7 @@ static void aer_enable_rootport(struct aer_rpc *rpc)
>  				   SYSTEM_ERROR_INTR_ON_MESG_MASK);
>  
>  	/* Clear error status */
> -	pci_read_config_dword(pdev, aer + PCI_ERR_ROOT_STATUS, &reg32);
> -	pci_write_config_dword(pdev, aer + PCI_ERR_ROOT_STATUS, reg32);
> -	pci_read_config_dword(pdev, aer + PCI_ERR_COR_STATUS, &reg32);
> -	pci_write_config_dword(pdev, aer + PCI_ERR_COR_STATUS, reg32);
> -	pci_read_config_dword(pdev, aer + PCI_ERR_UNCOR_STATUS, &reg32);
> -	pci_write_config_dword(pdev, aer + PCI_ERR_UNCOR_STATUS, reg32);
> +	pci_aer_raw_clear_status(pdev);

It's true that this is functionally equivalent.

But 20e15e673b05 ("PCI/AER: Add pci_aer_raw_clear_status() to
unconditionally clear Error Status") says pci_aer_raw_clear_status()
is only for use in the EDR path (this should have been included in the
function comment), so I think we should preserve that property and use
pci_aer_clear_status() here.

pci_aer_raw_clear_status() is the same as pci_aer_clear_status()
except it doesn't check pcie_aer_is_native().  And I'm pretty sure we
can't get to aer_enable_rootport() *unless* pcie_aer_is_native(),
because get_port_device_capability() checks the same thing, so they
should be equivalent here.

Bjorn