linux-kernel - Re: [PATCH] PCI/DPC: Allow Non-ACPI Native ports to use DPC

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Date:   Thu, 16 Apr 2020 13:32:51 -0700
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Jon Derrick <jonathan.derrick@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>
Cc:     Russell Currey <ruscur@...sell.cc>,
        Sam Bobroff <sbobroff@...ux.ibm.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Olof Johansson <olof@...om.net>,
        Keith Busch <keith.busch@...el.com>,
        Frederick Lawler <fred@...dlawl.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI/DPC: Allow Non-ACPI Native ports to use DPC

Hi,

On 4/16/20 12:59 PM, Jon Derrick wrote:
> Some platforms have a mix of ports whose capabilities can be negotiated
> by _OSC, and some ports which are not described by ACPI and instead
> managed by Native drivers. The existing Firmware-First HEST model can
> incorrectly tag these Native, Non-ACPI ports as Firmware-First capable
> ports by advertising the HEST Global flag and specifying the type and
> class (aer_hest_parse).
> 
> This ultimately can lead to bad situations if the BIOS or port firmware
> leaves DPC preconfigured and the Linux DPC driver is unable to bind to
> the port to handle DPC events.
> 
> This patch adds the check for Native DPC in the port's host bridge in
> order to allow DPC services to bind to the port.
> 
> Signed-off-by: Jon Derrick <jonathan.derrick@...el.com>
> ---
>   drivers/pci/pcie/dpc.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> index 7621704..a1e355d 100644
> --- a/drivers/pci/pcie/dpc.c
> +++ b/drivers/pci/pcie/dpc.c
> @@ -281,10 +281,12 @@ static int dpc_probe(struct pcie_device *dev)
>   {
>   	struct pci_dev *pdev = dev->port;
>   	struct device *device = &dev->device;
> +	struct pci_host_bridge *host = pci_find_host_bridge(pdev->bus);
>   	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 &&
For other PCIe services, this check is added in 
get_port_device_capability().
Why not add it there for DPC as well ?
> +	    !host->native_dpc)
>   		return -ENOTSUPP;
>   
>   	status = devm_request_threaded_irq(device, dev->irq, dpc_irq,
>