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

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Date:   Sun, 13 Sep 2020 13:54:38 -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 9/10/20 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.
>    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