linux-kernel - Re: [PATCH v11 2/5] ACPI/PCI: Ignore _OSC negotiation result if pcie_ports

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Message-ID: <20201125222509.GA688516@bjorn-Precision-5520>
Date:   Wed, 25 Nov 2020 16:25:09 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, ashok.raj@...el.com,
        knsathya@...nel.org
Subject: Re: [PATCH v11 2/5] ACPI/PCI: Ignore _OSC negotiation result if
 pcie_ports_native is set.

On Wed, Nov 25, 2020 at 02:21:49PM -0800, Kuppuswamy, Sathyanarayanan wrote:
> Hi Bjorn,
> 
> Thanks for the review.
> 
> On 11/25/20 12:12 PM, Bjorn Helgaas wrote:
> > On Mon, Oct 26, 2020 at 07:57:05PM -0700, Kuppuswamy Sathyanarayanan wrote:
> > > pcie_ports_native is set only if user requests native handling
> > > of PCIe capabilities via pcie_port_setup command line option.
> > > User input takes precedence over _OSC based control negotiation
> > > result. So consider the _OSC negotiated result only if
> > > pcie_ports_native is unset.
> > > 
> > > Also, since struct pci_host_bridge ->native_* members caches the
> > > ownership status of various PCIe capabilities, use them instead
> > > of distributed checks for pcie_ports_native.
> > > 
> > > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> > > ---
> > >   drivers/acpi/pci_root.c           | 35 ++++++++++++++++++++++---------
> > >   drivers/pci/hotplug/pciehp_core.c |  2 +-
> > >   drivers/pci/pci-acpi.c            |  3 ---
> > >   drivers/pci/pcie/aer.c            |  2 +-
> > >   drivers/pci/pcie/portdrv_core.c   |  9 +++-----
> > >   include/linux/acpi.h              |  2 ++
> > >   6 files changed, 32 insertions(+), 21 deletions(-)
> > > 
> > > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> > > index c12b5fb3e8fb..a9e6b782622d 100644
> > > --- a/drivers/acpi/pci_root.c
> > > +++ b/drivers/acpi/pci_root.c
> > > @@ -41,6 +41,12 @@ static int acpi_pci_root_scan_dependent(struct acpi_device *adev)
> > >   				| OSC_PCI_CLOCK_PM_SUPPORT \
> > >   				| OSC_PCI_MSI_SUPPORT)
> 
> > > +
> > > +	if (pcie_ports_native) {
> > > +		decode_osc_control(root, "OS forcibly taking over",
> > > +				   OSC_PCI_EXPRESS_CONTROL_MASKS);
> > 
> > The only place OSC_PCI_EXPRESS_CONTROL_MASKS is used is right here, so
> > it's kind of pointless.
> > 
> > I think I'd rather have this:
> > 
> >    dev_info(&root->device->dev, "Ignoring PCIe-related _OSC results because \"pcie_ports=native\" specified\n");
> I was trying to keep the same print format. In pci_root.c,
> decode_os_control() is repeatedly used to print info related to
> PCIe capability ownership.
> 
> But either way is fine with me. I can use the format you mentioned.
> > 
> > 
> > followed by something like this after we're done fiddling with all the
> > host_bridge->native* bits:
> > 
> 
> >    #define FLAG(x) ((x) ? '+' : '-')
> > 
> >    dev_info(&root->device->dev, "OS native features: SHPCHotplug%c PCIeCapability%c PCIeHotplug%c PME%c AER%c DPC%c LTR%c\n",
> >             FLAG(host_bridge->native_shpc_hotplug),
> > 	   ?,
> >             FLAG(host_bridge->native_pcie_hotplug),
> > 	   ...);
> > 
> > But I don't know how to handle OSC_PCI_EXPRESS_CAPABILITY_CONTROL
> > since we don't track it the same way.  Maybe we'd have to omit it from
> > this message for now?
> I will add it in next version. But for now, its not worry about
> OSC_PCI_EXPRESS_CAPABILITY_CONTROL.

I've been fiddling with this, so let me post a v12 tonight and you can
see what you think.

> > >   	/*
> > >   	 * Evaluate the "PCI Boot Configuration" _DSM Function.  If it
> 
> > > -- 
> > > 2.17.1
> > > 
> 
> -- 
> Sathyanarayanan Kuppuswamy
> Linux Kernel Developer