Re: [PATCH v8 2/5] ACPI/PCI: Ignore _OSC negotiation result if pcie_ports_native is set.

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On 9/10/20 1:14 PM, Bjorn Helgaas wrote:
On Fri, Jul 24, 2020 at 08:58:53PM -0700, sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
---
  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



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