linux-kernel - Re: [PATCH] PCI/AER: Enable SERR# forwarding in non ACPI flow

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Date:   Fri, 13 Jul 2018 10:44:38 +0530
From:   poza@...eaurora.org
To:     Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        bhelgaas@...gle.com, linux-pci-owner@...r.kernel.org
Subject: Re: [PATCH] PCI/AER: Enable SERR# forwarding in non ACPI flow

On 2018-07-12 20:15, Bharat Kumar Gogada wrote:
> Currently PCI_BRIDGE_CTL_SERR is being enabled only in
> ACPI flow.
> This bit is required for forwarding errors reported
> by EP devices to upstream device.
> This patch enables SERR# for Type-1 PCI device.
> 
> Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
> ---
>  drivers/pci/pcie/aer.c |   23 +++++++++++++++++++++++
>  1 files changed, 23 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index a2e8838..943e084 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -343,6 +343,19 @@ int pci_enable_pcie_error_reporting(struct pci_dev 
> *dev)
>  	if (!dev->aer_cap)
>  		return -EIO;
> 
> +	if (!IS_ENABLED(CONFIG_ACPI) &&
> +	    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);
> +		control |= PCI_BRIDGE_CTL_SERR;
> +		pci_write_config_word(dev, PCI_BRIDGE_CONTROL, control);
> +	}
> +
>  	return pcie_capability_set_word(dev, PCI_EXP_DEVCTL, 
> PCI_EXP_AER_FLAGS);
>  }
>  EXPORT_SYMBOL_GPL(pci_enable_pcie_error_reporting);
> @@ -352,6 +365,16 @@ int pci_disable_pcie_error_reporting(struct 
> pci_dev *dev)
>  	if (pcie_aer_get_firmware_first(dev))
>  		return -EIO;
> 
> +	if (!IS_ENABLED(CONFIG_ACPI) &&
> +	    dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
> +		u16 control;
> +
> +		/* Clear SERR Forwarding */
> +		pci_read_config_word(dev, PCI_BRIDGE_CONTROL, &control);
> +		control &= ~PCI_BRIDGE_CTL_SERR;
> +		pci_write_config_word(dev, PCI_BRIDGE_CONTROL, control);
> +	}
> +
>  	return pcie_capability_clear_word(dev, PCI_EXP_DEVCTL,
>  					  PCI_EXP_AER_FLAGS);
>  }


Should this configuration no be set by Firmware ? why should Linux 
dictate it ?

Regards,
Oza.