linux-kernel - Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device companion assignment to core code.

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Date:	Wed, 20 Jan 2016 14:40:08 +0100
From:	Tomasz Nowicki <tn@...ihalf.com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:	bhelgaas@...gle.com, arnd@...db.de, will.deacon@....com,
	catalin.marinas@....com, rjw@...ysocki.net, hanjun.guo@...aro.org,
	okaya@...eaurora.org, jiang.liu@...ux.intel.com,
	Stefano.Stabellini@...citrix.com,
	robert.richter@...iumnetworks.com, mw@...ihalf.com,
	Liviu.Dudau@....com, ddaney@...iumnetworks.com, tglx@...utronix.de,
	wangyijing@...wei.com, Suravee.Suthikulpanit@....com,
	msalter@...hat.com, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org,
	jchandra@...adcom.com, jcm@...hat.com
Subject: Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device
 companion assignment to core code.

On 20.01.2016 13:38, Lorenzo Pieralisi wrote:
> On Wed, Jan 20, 2016 at 12:20:07PM +0100, Tomasz Nowicki wrote:
>> On 19.01.2016 17:02, Lorenzo Pieralisi wrote:
>>> On Wed, Jan 13, 2016 at 02:20:57PM +0100, Tomasz Nowicki wrote:
>> [...]
>>>> device via pci_create_root_bus parameter (as the ACPI device type)
>>>
>>> I do not understand what you mean by "as the ACPI device type".
>>
>> See below.
>>
>>>
>>>> and using ACPI_COMPANION_SET in core code for ACPI boot method.
>>>> ACPI_COMPANION_SET is safe to run for all cases DT, ACPI and DT&ACPI.
>>>>
>>>> Suggested-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
>>>> Signed-off-by: Tomasz Nowicki <tn@...ihalf.com>
>>>> ---
>>>>   drivers/acpi/pci_root.c | 5 ++++-
>>>>   drivers/pci/probe.c     | 2 ++
>>>>   2 files changed, 6 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
>>>> index ae3fe4e..a65c8c2 100644
>>>> --- a/drivers/acpi/pci_root.c
>>>> +++ b/drivers/acpi/pci_root.c
>>>> @@ -846,7 +846,10 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
>>>>
>>>>   	pci_acpi_root_add_resources(info);
>>>>   	pci_add_resource(&info->resources, &root->secondary);
>>>> -	bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
>>>> +
>>>> +	/* Root bridge device needs to be sure of parent ACPI type */
>>>> +	ACPI_COMPANION_SET(&device->dev, device);
>>>
>>> I do not understand why the code above is needed, can you elaborate
>>> please ?
>>>
>>
>> This makes sure that device->dev can be identified as ACPI device,
>> so we can use to_acpi_device_node() and assign companion safely
>> below.
>
> I do not follow. If you refer to the fwnode handle type, that is
> already set by ACPI core code (before acpi_pci_root_add() is called,
> in acpi_init_device_object()).

acpi_init_device_object() sets ACPI fwnode handle type only for 
"device", but not for "device->dev" which is what is passed as an 
argument to pci_create_root_bus().

Without ACPI_COMPANION_SET(&device->dev, device) here, no one can be 
sure if we have ACPI device in pci_create_root_bus().

>
> Did you add the code above to solve a real issue you encountered ?
Yes. You can try to run series with this patch:

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 88c9d20..1b74bf6 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -967,7 +967,11 @@ struct pci_bus *acpi_pci_root_create(struct 
acpi_pci_root *root,
         pci_add_resource(&info->resources, &root->secondary);

-        /* Root bridge device needs to be sure of parent ACPI type */
-       ACPI_COMPANION_SET(&device->dev, device);
+       if (to_acpi_device_node(device->dev.fwnode) == NULL)
+               pr_err("NON-ACPI TYPE\n");
+       else
+               pr_err("ACPI TYPE\n");
+
         bus = pci_create_root_bus(&device->dev, busnum, ops->pci_ops,
                                   sysdata, &info->resources);


Thanks,
Tomasz