linux-kernel - Re: [PATCH v2 2/2] PCI/DPC: Allow Native DPC Host Bridges to use DPC

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Date:   Wed, 22 Apr 2020 15:50:17 -0700
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Jon Derrick <jonathan.derrick@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>
Cc:     linux-pci@...r.kernel.org, Keith Busch <kbusch@...nel.org>,
        Russell Currey <ruscur@...sell.cc>,
        Sam Bobroff <sbobroff@...ux.ibm.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Frederick Lawler <fred@...dlawl.com>,
        Rajat Jain <rajatja@...gle.com>,
        "Patel, Mayurkumar" <mayurkumar.patel@...el.com>,
        Olof Johansson <olof@...om.net>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] PCI/DPC: Allow Native DPC Host Bridges to use DPC



On 4/20/20 2:37 PM, Jon Derrick wrote:
> The existing portdrv model prevents DPC services without either OS
> control (_OSC) granted to AER services, a Host Bridge requesting Native
> AER, or using one of the 'pcie_ports=' parameters of 'native' or
> 'dpc-native'.
> 
> The DPC port service driver itself will also fail to probe if the kernel
> assumes the port is using Firmware-First AER. It's a reasonable
> expectation that a port using Firmware-First AER will also be using
> Firmware-First DPC, however if a Host Bridge requests Native DPC, the
> DPC driver should allow it and not fail to bind due to AER capability
> settings.
> 
> Host Bridges which request Native DPC port services will also likely
> request Native AER, however it shouldn't be a requirement. This patch
> allows ports on those Host Bridges to have DPC port services.
> 
> This will avoid the unlikely situation where the port is Firmware-First
> AER and Native DPC, and a BIOS or switch firmware preconfiguration of
> the DPC trigger could result in unhandled DPC events.
> 
> Signed-off-by: Jon Derrick <jonathan.derrick@...el.com>
> ---
>   drivers/pci/pcie/dpc.c          | 3 ++-
>   drivers/pci/pcie/portdrv_core.c | 3 ++-
>   2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> index 7621704..3f3106f 100644
> --- a/drivers/pci/pcie/dpc.c
> +++ b/drivers/pci/pcie/dpc.c
> @@ -284,7 +284,8 @@ static int dpc_probe(struct pcie_device *dev)
>   	int status;
>   	u16 ctl, cap;
>   
> -	if (pcie_aer_get_firmware_first(pdev) && !pcie_ports_dpc_native)
> +	if (pcie_aer_get_firmware_first(pdev) && !pcie_ports_dpc_native &&
> +	    !pci_find_host_bridge(pdev->bus)->native_dpc)
Why do it in probe as well ? if host->native_dpc is not set then the
device DPC probe it self won't happen right ?
>   		return -ENOTSUPP;
>   
>   	status = devm_request_threaded_irq(device, dev->irq, dpc_irq,
> diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
> index 50a9522..f2139a1 100644
> --- a/drivers/pci/pcie/portdrv_core.c
> +++ b/drivers/pci/pcie/portdrv_core.c
> @@ -256,7 +256,8 @@ static int get_port_device_capability(struct pci_dev *dev)
>   	 */
>   	if (pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DPC) &&
>   	    pci_aer_available() &&
> -	    (pcie_ports_dpc_native || (services & PCIE_PORT_SERVICE_AER)))
> +	    (pcie_ports_dpc_native || host->native_dpc ||
> +	     (services & PCIE_PORT_SERVICE_AER)))
>   		services |= PCIE_PORT_SERVICE_DPC;
>   
>   	if (pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM ||
>