linux-kernel - Re: [PATCH v5 1/5] PCI: Consistently report presence of PCIe link registers

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Date:   Mon, 7 Nov 2022 15:27:38 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, Stefan Roese <sr@...x.de>,
        Jim Wilson <wilson@...iptree.org>,
        David Abdurachmanov <david.abdurachmanov@...il.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/5] PCI: Consistently report presence of PCIe link
 registers

On Sat, Sep 17, 2022 at 01:03:09PM +0100, Maciej W. Rozycki wrote:
> Consistently with commit c8b303d0206b ("PCI: Remove PCIe Capability 
> version checks") only consider the PCI Express capability's Link Control 
> 2, etc. registers present if the Link Control register is.
> 
> Before said commit with PCI Express capability versions higher than one 
> all link registers used to be considered present, however starting from 
> said commit Link Control, etc. original registers are only considered 
> present in devices with links, but Link Control 2, etc. registers 
> continue being considered always present even though likewise they are 
> only present in devices with links.
> 
> Fix the inconsistency then.
> 
> Signed-off-by: Maciej W. Rozycki <macro@...am.me.uk>

While we figure out the rest of this, I squashed the first two patches
and applied them to pci/enumeration for v6.2:

  commit 503fa23614dc ("PCI: Access Link 2 registers only for devices with Links")
  Author: Maciej W. Rozycki <macro@...am.me.uk>
  Date:   Sat Sep 17 13:03:09 2022 +0100

    PCI: Access Link 2 registers only for devices with Links

    PCIe r2.0, sec 7.8 added Link Capabilities/Status/Control 2 registers to
    the PCIe Capability with Capability Version 2.

    Previously we assumed these registers were implemented for all PCIe
    Capabilities of version 2 or greater, but in fact they are only
    implemented for devices with Links.

    Update pcie_capability_reg_implemented() to check whether the device has
    a Link.

> ---
> New change in v5.
> ---
>  drivers/pci/access.c |    8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> linux-pcie-cap-has-lnkctl2.diff
> Index: linux-macro/drivers/pci/access.c
> ===================================================================
> --- linux-macro.orig/drivers/pci/access.c
> +++ linux-macro/drivers/pci/access.c
> @@ -350,6 +350,11 @@ bool pcie_cap_has_lnkctl(const struct pc
>  	       type == PCI_EXP_TYPE_PCIE_BRIDGE;
>  }
>  
> +static inline bool pcie_cap_has_lnkctl2(const struct pci_dev *dev)
> +{
> +	return pcie_cap_has_lnkctl(dev) && pcie_cap_version(dev) > 1;
> +}
> +
>  static inline bool pcie_cap_has_sltctl(const struct pci_dev *dev)
>  {
>  	return pcie_downstream_port(dev) &&
> @@ -390,10 +395,11 @@ static bool pcie_capability_reg_implemen
>  		return pcie_cap_has_rtctl(dev);
>  	case PCI_EXP_DEVCAP2:
>  	case PCI_EXP_DEVCTL2:
> +		return pcie_cap_version(dev) > 1;
>  	case PCI_EXP_LNKCAP2:
>  	case PCI_EXP_LNKCTL2:
>  	case PCI_EXP_LNKSTA2:
> -		return pcie_cap_version(dev) > 1;
> +		return pcie_cap_has_lnkctl2(dev);
>  	default:
>  		return false;
>  	}