Re: [PATCH] PCI / PCIe: Ask BIOS for control of all native services at once (v4)

[Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>]

(2010/07/29 6:43), Jesse Barnes wrote:
> On Wed, 28 Jul 2010 23:23:56 +0200
> "Rafael J. Wysocki"<rjw@sisk.pl>  wrote:
>
>> From: Rafael J. Wysocki<rjw@sisk.pl>
>>
>> PCIe port service drivers ask the BIOS, through _OSC, for control of
>> the services they handle.  Unfortunately, each of them individually
>> asks for control of the PCIe capability structure and if that is
>> granted, some BIOSes expect that the other PCIe port services will be
>> configured and handled by the kernel as well.  If that is not the
>> case (eg. one of the PCIe port service drivers is not loaded), the
>> BIOS may be confused and may cause the system as a whole to misbehave
>> (eg. on one of such systems enabling the native PCIe PME service
>> without loading the native PCIe hot-plug service driver causes a
>> storm of ACPI notify requests to appear).
>>
>> For this reason rework the PCIe port driver so that (1) it checks
>> which native PCIe port services can be enabled, according to the
>> BIOS, and (2) it requests control of all these services
>> simultaneously.  In particular, this causes pcie_portdrv_probe() to
>> fail if the BIOS refuses to grant control of the PCIe capability
>> structure, which means that no native PCIe port services can be
>> enabled for the PCIe root complex the given port belongs to.
>>
>> Make it possible to override this behavior using a new command line
>> switch pcie_ports= that can be set to 'auto' (ask the BIOS, the
>> default), 'native' (use the PCIe native services regardless of the
>> BIOS response to the control request), or 'compat' (do not use the
>> PCIe native services at all).
>>
>> Accordingly, rework the existing PCIe port service drivers so that
>> they don't request control of the services directly.
>>
>> Signed-off-by: Rafael J. Wysocki<rjw@sisk.pl>
>> ---
>
> Kenji-san, are you ok with this version?  I would like to get your ack
> (and ideally your tested-by) for this one since it affects
> functionality you need.
>

Hi Jesse, Rafael,

I've just started reviewing the latest version of the patch. I have good
impression about this version so far. Please give me a few days for deeper
review. And I've booked the test machine for this patch in next week. I'll
try to test the patch and send you the result as soon as I can.

Here are two comments I have so far.

Though it is not directly related to Rafael's patch, I found one problem
in _OSC query handling while reviewing this patch. Currently, all the
_OSC controls are queried at the same time in acpi_pci_osc_support() and
the result is preserved for later acpi_pci_osc_control_set() call. But
query result can vary depending on the combination of requested controls.
So I think query result must not be preserved. Since Rafael's patch uses
query result, this problem should be fixed at the same time. I'll try to
make a patch for this and update Rafael's patch if needed.


I think the following changes should be done in the separated patch. I
guess this change is for the BIOS which enables hotplug interrupt at when
_OSC is evaluated with native hot-plug control. Right? Anyway, it should
be separated patch with appropriate description.

+			/*
+			 * Disable hot-plug interrupts in case the hot-plug
+			 * service driver is not loaded.
+			 */
+			pos += PCI_EXP_SLTCTL;
+			pci_read_config_word(dev, pos, &reg16);
+			reg16 &= ~(PCI_EXP_SLTCTL_CCIE | PCI_EXP_SLTCTL_HPIE);
+			pci_write_config_word(dev, pos, reg16);

Thanks,
Kenji Kaneshige