linux-kernel - Re: [PATCH v8 2/5] ACPI/PCI: Ignore _OSC negotiation result if pcie_ports

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Date:   Tue, 15 Sep 2020 19:33:39 -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 2/5] ACPI/PCI: Ignore _OSC negotiation result if
 pcie_ports_native is set.



On 9/15/20 3:20 PM, Bjorn Helgaas wrote:
> On Sun, Sep 13, 2020 at 01:54:38PM -0700, Kuppuswamy, Sathyanarayanan wrote:
>> On 9/10/20 1:14 PM, Bjorn Helgaas wrote:
>>> On Fri, Jul 24, 2020 at 08:58:53PM -0700, sathyanarayanan.kuppuswamy@...ux.intel.com wrote:
>>>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>>>>
>>>> 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           | 61 ++++++++++++++++++++++++++-----
>>>>    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 ++---
>>>>    5 files changed, 56 insertions(+), 21 deletions(-)
>>>>
>>>> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
>>>> index f90e841c59f5..f8981d4e044d 100644
>>>> --- a/drivers/acpi/pci_root.c
>>>> +++ b/drivers/acpi/pci_root.c
>>>> @@ -145,6 +145,17 @@ static struct pci_osc_bit_struct pci_osc_control_bit[] = {
>>>>    	{ OSC_PCI_EXPRESS_DPC_CONTROL, "DPC" },
>>>>    };
>>
>>>> +		else
>>>> +			dev_warn(&bus->dev, "OS overrides %s firmware control",
>>>> +			get_osc_desc(OSC_PCI_EXPRESS_NATIVE_HP_CONTROL));
>>>
>>> There's got to be a way to write this more concisely.  Maybe something
>>> like this?
>>>
>>>     #define OSC_OWNER(ctrl, bit, flag) \
>>>       if (!(ctrl & bit)) \
>>>         flag = 0;
>>>
>>>     if (pcie_ports_native)
>>>       decode_osc_control(root, "OS forcibly taking over", ~0);
>>
>> BIT1 and BIT6 does not have PCIe dependency. And BIT7-31 are reserved.
>> So we can't force all _OSC bits based on pcie_ports_native value.
>> So, IM0, its better to handle PCIe features seperatly.
> 
> Yes, we may need to handle a few bits specially.  But we need to
> figure out a nicer-looking way of coding this.  It's too cumbersome to
> check pcie_ports_native and log a message for every _OSC bit
> individually.
ok. Let me check how to simplify it.
> 
>>>     else {
>>>       ctrl = root->osc_control_set;
>>>       OSC_OWNER(ctrl, OSC_PCI_EXPRESS_AER_CONTROL, host_bridge->native_aer);
>>>       OSC_OWNER(ctrl, OSC_PCI_EXPRESS_PME_CONTROL, host_bridge->native_pme);
>>>       ...
>>>     }
>>
>>
>> -- 
>> Sathyanarayanan Kuppuswamy
>> Linux Kernel Developer

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer