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

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Date:   Wed, 25 Nov 2020 16:58:28 -0800
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
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 11/25/20 12:28 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.
> 
>> 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)
ok. I can add this fix on top of your update.
> 
> 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)
We already use it in pci_root.c to confirm AER availability before
we request control over it via _OSC. So if pci_aer_available() is false
OSC_*AER_CONTROL bit in ctrl_set will be left zero (which means
->native_aer will also be zero).

490         if (pci_aer_available())
491                 control |= OSC_PCI_EXPRESS_AER_CONTROL;

So, may we don't need pci_aer_available() check here.

> 
>>   		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)
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer