linux-kernel - Re: [PATCH] PCI / ACPI: Make acpiphp ignore root bridges using PCIe native hotplug

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Date:	Wed, 26 Oct 2011 09:28:46 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Linux PCI <linux-pci@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	ACPI Devel Mailing List <linux-acpi@...r.kernel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>
Subject: Re: [PATCH] PCI / ACPI: Make acpiphp ignore root bridges using PCIe
 native hotplug

(2011/10/25 22:25), Rafael J. Wysocki wrote:
> On Tuesday, October 25, 2011, Kenji Kaneshige wrote:
>> Looks good.
>> This is also needed for SHPC native hotplug.
> 
> I don't think so, we still leave the SHPC _OSC for the driver to take care
> of (which may not be the right thing, but I don't feel confident enough to
> decide :-)).

I think of the case that acpiphp driver is loaded after shpchp driver is unloaded.
Once native hotplug control is granted to OS, there is no way to return the control
to firmware. So once shpchp gets the native hotplug control on a given root bridge,
acpiphp should not try to handle the hotplug slots under it.

Regards,
Kenji Kaneshige


> 
> Thanks,
> Rafael
> 
> 
>> (2011/10/22 7:43), Rafael J. Wysocki wrote:
>>> From: Rafael J. Wysocki<rjw@...k.pl>
>>>
>>> If the kernel has requested control of the PCIe native hotplug
>>> feature for a given root complex, the acpiphp driver should not try
>>> to handle that root complex and it should leave it to pciehp.
>>> Failing to do so causes problems to happen if acpiphp is loaded
>>> before pciehp on such systems.
>>>
>>> To address this issue make find_root_bridges() ignore PCIe root
>>> complexes with PCIe native hotplug enabled and make add_bridge()
>>> return error code if PCIe native hotplug is enabled for the given
>>> root port.  This causes acpiphp to refuse to load if PCIe native
>>> hotplug is enabled for all complexes and to refuse binding to
>>> the root complexes with PCIe native hotplug is enabled.
>>>
>>> Signed-off-by: Rafael J. Wysocki<rjw@...k.pl>
>>> ---
>>>    drivers/pci/hotplug/acpiphp_glue.c |   29 ++++++++++++++++++++++++-----
>>>    1 file changed, 24 insertions(+), 5 deletions(-)
>>>
>>> Index: linux/drivers/pci/hotplug/acpiphp_glue.c
>>> ===================================================================
>>> --- linux.orig/drivers/pci/hotplug/acpiphp_glue.c
>>> +++ linux/drivers/pci/hotplug/acpiphp_glue.c
>>> @@ -458,8 +458,17 @@ static int add_bridge(acpi_handle handle
>>>    {
>>>    	acpi_status status;
>>>    	unsigned long long tmp;
>>> +	struct acpi_pci_root *root;
>>>    	acpi_handle dummy_handle;
>>>
>>> +	/*
>>> +	 * We shouldn't use this bridge if PCIe native hotplug control has been
>>> +	 * granted by the BIOS for it.
>>> +	 */
>>> +	root = acpi_pci_find_root(handle);
>>> +	if (root&&   (root->osc_control_set&   OSC_PCI_EXPRESS_NATIVE_HP_CONTROL))
>>> +		return -ENODEV;
>>> +
>>>    	/* if the bridge doesn't have _STA, we assume it is always there */
>>>    	status = acpi_get_handle(handle, "_STA",&dummy_handle);
>>>    	if (ACPI_SUCCESS(status)) {
>>> @@ -1297,13 +1306,23 @@ static void handle_hotplug_event_func(ac
>>>    static acpi_status
>>>    find_root_bridges(acpi_handle handle, u32 lvl, void *context, void **rv)
>>>    {
>>> +	struct acpi_pci_root *root;
>>>    	int *count = (int *)context;
>>>
>>> -	if (acpi_is_root_bridge(handle)) {
>>> -		acpi_install_notify_handler(handle, ACPI_SYSTEM_NOTIFY,
>>> -				handle_hotplug_event_bridge, NULL);
>>> -			(*count)++;
>>> -	}
>>> +	if (!acpi_is_root_bridge(handle))
>>> +		return AE_OK;
>>> +
>>> +	root = acpi_pci_find_root(handle);
>>> +	if (!root)
>>> +		return AE_OK;
>>> +
>>> +	if (root->osc_control_set&   OSC_PCI_EXPRESS_NATIVE_HP_CONTROL)
>>> +		return AE_OK;
>>> +
>>> +	(*count)++;
>>> +	acpi_install_notify_handler(handle, ACPI_SYSTEM_NOTIFY,
>>> +				    handle_hotplug_event_bridge, NULL);
>>> +
>>>    	return AE_OK ;
>>>    }
>>>
>>> --
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>>>
>>
>>
>>
> 
> 

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