linux-kernel - Re: [PATCH v8 1/5] PCI: Conditionally initialize host bridge native

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Date:   Sun, 13 Sep 2020 13:49:26 -0700
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
Subject: Re: [PATCH v8 1/5] PCI: Conditionally initialize host bridge native_*
 members



On 9/10/20 2:00 PM, Kuppuswamy, Sathyanarayanan wrote:
> 
> 
> On 9/10/20 12:49 PM, Bjorn Helgaas wrote:
>> On Fri, Jul 24, 2020 at 08:58:52PM -0700, sathyanarayanan.kuppuswamy@...ux.intel.com wrote:
>>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>>>
>>> If CONFIG_PCIEPORTBUS is not enabled in kernel then initialing
>>> struct pci_host_bridge PCIe specific native_* members to "1" is
>>> incorrect. So protect the PCIe specific member initialization
>>> with CONFIG_PCIEPORTBUS.
>>
>> s/initialing/initializing/
> will fix it in next version.
>>
>>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>>> ---
>>>   drivers/pci/probe.c | 4 +++-
>>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>>> index 2f66988cea25..a94b97564ceb 100644
>>> --- a/drivers/pci/probe.c
>>> +++ b/drivers/pci/probe.c
>>> @@ -588,12 +588,14 @@ static void pci_init_host_bridge(struct pci_host_bridge *bridge)
>>>        * may implement its own AER handling and use _OSC to prevent the
>>>        * OS from interfering.
>>>        */
>>> +#ifdef CONFIG_PCIEPORTBUS
>>>       bridge->native_aer = 1;
>>>       bridge->native_pcie_hotplug = 1;
>>> -    bridge->native_shpc_hotplug = 1;
>>>       bridge->native_pme = 1;
>>>       bridge->native_ltr = 1;
>>
>> native_ltr isn't dependent on PCIEPORTBUS either, is it?  It's only
>> used for ASPM.
> Agreed. I was confused due to a comment in include/linux/pci.h
> 
>   unsigned int    native_ltr:1;           /* OS may use PCIe LTR */
Currently there is no code dependency between LTR and CONFIG_PCIEPORTBUS.

But I am wondering whether its correct to move LTR code under
CONFIG_PCIEPORTBUS?. As per PCIe spec v5.0 sec 7.8.2, LTR is a optional
PCIe extended capability. So why is not moved under drivers/pci/pcie/*. What is
the criteria for code to be placed under drivers/pci/pcie/*
> 
>>
>>>       bridge->native_dpc = 1;
>>> +#endif
>>> +    bridge->native_shpc_hotplug = 1;
>>>       device_initialize(&bridge->dev);
>>>   }
>>> -- 
>>> 2.17.1
>>>
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer