netdev - Re: [PATCH 2/3] ARM: iop32x: improve N2100 PCI broken parity quirk

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Date:   Tue, 5 Jan 2021 18:28:33 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 2/3] ARM: iop32x: improve N2100 PCI broken parity quirk

On Tue, Jan 05, 2021 at 10:42:31AM +0100, Heiner Kallweit wrote:
> Simplify the quirk by using new PCI core function
> pci_quirk_broken_parity(). In addition make the quirk
> more specific, use device id 0x8169 instead of PCI_ANY_ID.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> ---
>  arch/arm/mach-iop32x/n2100.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/mach-iop32x/n2100.c b/arch/arm/mach-iop32x/n2100.c
> index 78b9a5ee4..24c3eec46 100644
> --- a/arch/arm/mach-iop32x/n2100.c
> +++ b/arch/arm/mach-iop32x/n2100.c
> @@ -122,12 +122,10 @@ static struct hw_pci n2100_pci __initdata = {
>   */
>  static void n2100_fixup_r8169(struct pci_dev *dev)
>  {
> -	if (dev->bus->number == 0 &&
> -	    (dev->devfn == PCI_DEVFN(1, 0) ||
> -	     dev->devfn == PCI_DEVFN(2, 0)))
> -		dev->broken_parity_status = 1;
> +	if (machine_is_n2100())
> +		pci_quirk_broken_parity(dev);

Whatever "machine_is_n2100()" is (I can't find the definition), it is
surely not equivalent to "00:01.0 || 00:02.0".  That change probably
should be a separate patch with some explanation.

If this makes the quirk safe to use in a generic kernel, that sounds
like a good thing.

I guess a parity problem could be the result of a defect in either the
device (e.g., 0x8169), which would be an issue in *all* platforms, or
a platform-specific issue in the way it's wired up.  I assume it's the
latter because the quirk is not in drivers/pci/quirks.c.

Why is it safe to restrict this to device ID 0x8169?  If this is
platform issue, it might affect any device in the slot.

>  }
> -DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_REALTEK, PCI_ANY_ID, n2100_fixup_r8169);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_REALTEK, 0x8169, n2100_fixup_r8169);
>  
>  static int __init n2100_pci_init(void)
>  {
> -- 
> 2.30.0
> 
>