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

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Message-ID: <20201125202810.GA674732@bjorn-Precision-5520>
Date:   Wed, 25 Nov 2020 14:28:10 -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 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.

> diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
> index 50a9522ab07d..ccd5e0ce5605 100644
> --- a/drivers/pci/pcie/portdrv_core.c
> +++ b/drivers/pci/pcie/portdrv_core.c
> @@ -208,8 +208,7 @@ static int get_port_device_capability(struct pci_dev *dev)
>  	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
>  	int services = 0;
>  
> -	if (dev->is_hotplug_bridge &&
> -	    (pcie_ports_native || host->native_pcie_hotplug)) {
> +	if (dev->is_hotplug_bridge && host->native_pcie_hotplug) {

This is a nit, but I think this and similar checks should be reordered
so we do the most generic test first, i.e.,

  if (host->native_pcie_hotplug && dev->is_hotplug_bridge)

Logically there's no point in looking at the device things if we
don't have native control.

>  		services |= PCIE_PORT_SERVICE_HP;
>  
>  		/*
> @@ -221,8 +220,7 @@ static int get_port_device_capability(struct pci_dev *dev)
>  	}
>  
>  #ifdef CONFIG_PCIEAER
> -	if (dev->aer_cap && pci_aer_available() &&
> -	    (pcie_ports_native || host->native_aer)) {
> +	if (dev->aer_cap && pci_aer_available() && host->native_aer) {

Can't we clear host->native_aer when pci_aer_available() returns
false?  I'd like to have all the checks about whether we have native
control to be in one place instead of being scattered.  Something like
this above:

  OSC_OWNER(ctrl, OSC_PCI_EXPRESS_AER_CONTROL, host_bridge->native_aer);
  if (!pci_aer_available())
    host_bridge->native_aer = 0;

So this test would become:

  if (host->native_aer && dev->aer_cap)

>  		services |= PCIE_PORT_SERVICE_AER;
>  
>  		/*
> @@ -238,8 +236,7 @@ static int get_port_device_capability(struct pci_dev *dev)
>  	 * Event Collectors can also generate PMEs, but we don't handle
>  	 * those yet.
>  	 */
> -	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT &&
> -	    (pcie_ports_native || host->native_pme)) {
> +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT && host->native_pme) {
>  		services |= PCIE_PORT_SERVICE_PME;

Also here:

  if (host->native_pme && pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)