linux-kernel - RE: [PATCH] PCI: Enable SERR# forwarding for Type-1 PCI devices

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Date:   Thu, 6 Dec 2018 15:47:13 +0000
From:   Bharat Kumar Gogada <bharatku@...inx.com>
To:     Bharat Kumar Gogada <bharatku@...inx.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        Ravikiran Gummaluri <rgummal@...inx.com>
Subject: RE: [PATCH] PCI: Enable SERR# forwarding for Type-1 PCI devices

Hi All,

Please let me know if anyone has any issue with this patch.

Regards,
Bharat
> As per Figure 6-3 in PCIe r4.0, sec 6.2.6, ERR_ messages will be forwarded
> from the secondary interface to the primary interface, if the SERR# Enable
> bit in the Bridge Control register is set.
> Currently PCI_BRIDGE_CTL_SERR is being enabled only in ACPI flow.
> This patch enables PCI_BRIDGE_CTL_SERR for Type-1 PCI device.
> 
> Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
> ---
>  drivers/pci/probe.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index
> b1c05b5..ed71e8e 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1841,8 +1841,6 @@ static void program_hpp_type0(struct pci_dev
> *dev, struct hpp_type0 *hpp)
>  		pci_write_config_byte(dev, PCI_SEC_LATENCY_TIMER,
>  				      hpp->latency_timer);
>  		pci_read_config_word(dev, PCI_BRIDGE_CONTROL,
> &pci_bctl);
> -		if (hpp->enable_serr)
> -			pci_bctl |= PCI_BRIDGE_CTL_SERR;
>  		if (hpp->enable_perr)
>  			pci_bctl |= PCI_BRIDGE_CTL_PARITY;
>  		pci_write_config_word(dev, PCI_BRIDGE_CONTROL,
> pci_bctl); @@ -2114,6 +2112,23 @@ static void
> pci_configure_eetlp_prefix(struct pci_dev *dev)  #endif  }
> 
> +static void pci_configure_serr(struct pci_dev *dev) {
> +	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
> +		u16 control;
> +
> +		/*
> +		 * A Type-1 PCI bridge will not forward ERR_ messages
> coming
> +		 * from an endpoint if SERR# forwarding is not enabled.
> +		 */
> +		pci_read_config_word(dev, PCI_BRIDGE_CONTROL,
> &control);
> +		if (!(control & PCI_BRIDGE_CTL_SERR)) {
> +			control |= PCI_BRIDGE_CTL_SERR;
> +			pci_write_config_word(dev, PCI_BRIDGE_CONTROL,
> control);
> +		}
> +	}
> +}
> +
>  static void pci_configure_device(struct pci_dev *dev)  {
>  	struct hotplug_params hpp;
> @@ -2124,6 +2139,7 @@ static void pci_configure_device(struct pci_dev
> *dev)
>  	pci_configure_relaxed_ordering(dev);
>  	pci_configure_ltr(dev);
>  	pci_configure_eetlp_prefix(dev);
> +	pci_configure_serr(dev);
> 
>  	memset(&hpp, 0, sizeof(hpp));
>  	ret = pci_get_hp_params(dev, &hpp);
> --
> 2.7.4