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

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Message-ID: <94fcbe2c950f9cff45c759b8598af985235ab932.camel@intel.com>
Date:   Thu, 16 Apr 2020 20:50:06 +0000
From:   "Derrick, Jonathan" <jonathan.derrick@...el.com>
To:     "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "helgaas@...nel.org" <helgaas@...nel.org>
CC:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "sbobroff@...ux.ibm.com" <sbobroff@...ux.ibm.com>,
        "olof@...om.net" <olof@...om.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "ruscur@...sell.cc" <ruscur@...sell.cc>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "kbusch@...nel.org" <kbusch@...nel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "oohall@...il.com" <oohall@...il.com>,
        "fred@...dlawl.com" <fred@...dlawl.com>
Subject: Re: [PATCH] PCI/DPC: Allow Non-ACPI Native ports to use DPC

On Thu, 2020-04-16 at 13:32 -0700, Kuppuswamy, Sathyanarayanan wrote:
> 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 ?

Sure. Looking at this, it seems like it needs some more de-tangling to
fit into my model.

> > +	    !host->native_dpc)
> >   		return -ENOTSUPP;
> >   
> >   	status = devm_request_threaded_irq(device, dev->irq, dpc_irq,
> >