linux-kernel - Re: [PATCH] pci: Don't set RCB bit in LNKCTL if the upstream bridge hasn't

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Message-ID: <20161026194317.GC17507@bhelgaas-glaptop.roam.corp.google.com>
Date:   Wed, 26 Oct 2016 14:43:17 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Johannes Thumshirn <jthumshirn@...e.de>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Yinghai Lu <yinghai@...nel.org>,
        Hannes Reinecke <hare@...e.de>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pci: Don't set RCB bit in LNKCTL if the upstream bridge
 hasn't

Hi Johannes,

On Wed, Oct 26, 2016 at 03:53:34PM +0200, Johannes Thumshirn wrote:
> The Read Completion Boundary bit must only be set on a device or endpoint if
> it is set on the upstream bridge.
> 
> Fixes: 7a1562d4f ("PCI: Apply _HPX Link Control settings to all devices with a link")

Can you please include a spec citation and a pointer to the bug report?

> Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de>
> ---
>  drivers/pci/probe.c | 26 ++++++++++++++++++++++++--
>  1 file changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index ab00267..5007b96 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1439,6 +1439,16 @@ static void program_hpp_type1(struct pci_dev *dev, struct hpp_type1 *hpp)
>  		dev_warn(&dev->dev, "PCI-X settings not supported\n");
>  }
>  
> +static bool pcie_get_upstream_rcb(struct pci_dev *dev)
> +{
> +	struct pci_dev *bridge = pci_upstream_bridge(dev);
> +	u16 lnkctl;
> +
> +	pcie_capability_read_word(bridge, PCI_EXP_LNKCTL, &lnkctl);
> +
> +	return lnkctl & PCI_EXP_LNKCTL_RCB;
> +}
> +
>  static void program_hpp_type2(struct pci_dev *dev, struct hpp_type2 *hpp)
>  {
>  	int pos;
> @@ -1468,9 +1478,21 @@ static void program_hpp_type2(struct pci_dev *dev, struct hpp_type2 *hpp)
>  			~hpp->pci_exp_devctl_and, hpp->pci_exp_devctl_or);
>  
>  	/* Initialize Link Control Register */
> -	if (pcie_cap_has_lnkctl(dev))
> +	if (pcie_cap_has_lnkctl(dev)) {
> +		bool us_rcb;
> +		u16 clear;
> +		u16 set;
> +
> +		us_rcb = pcie_get_upstream_rcb(dev);
> +
> +		clear = ~hpp->pci_exp_lnkctl_and;
> +		set = hpp->pci_exp_lnkctl_or;
> +		if (!us_rcb)
> +			set &= ~PCI_EXP_LNKCTL_RCB;
> +
>  		pcie_capability_clear_and_set_word(dev, PCI_EXP_LNKCTL,
> -			~hpp->pci_exp_lnkctl_and, hpp->pci_exp_lnkctl_or);
> +						  clear, set);
> +	}
>  
>  	/* Find Advanced Error Reporting Enhanced Capability */
>  	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
> -- 
> 1.8.5.6
> 
> --
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