Re: [Nouveau] [PATCH 4/4] drm/nouveau/acpi: fix lockup with PCIe runtime PM

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 27-05-16 13:10, Peter Wu wrote:
> On Wed, May 25, 2016 at 04:55:35PM +0300, Mika Westerberg wrote:
>> On Wed, May 25, 2016 at 12:53:01AM +0200, Peter Wu wrote:
>>> Since "PCI: Add runtime PM support for PCIe ports", the parent PCIe port
>>> can be runtime-suspended which disables power resources via ACPI. This
>>> is incompatible with DSM, resulting in a GPU device which is still in D3
>>> and locks up the kernel on resume.
>>>
>>> Mirror the behavior of Windows 8 and newer[1] (as observed via an AMLi
>>> debugger trace) and stop using the DSM functions for D3cold when power
>>> resources are available on the parent PCIe port.
>>>
>>>  [1]: https://msdn.microsoft.com/windows/hardware/drivers/bringup/firmware-requirements-for-d3cold
>>>
>>> Signed-off-by: Peter Wu <peter@lekensteyn.nl>
>>> ---
>>>  drivers/gpu/drm/nouveau/nouveau_acpi.c | 34 ++++++++++++++++++++++++++++++----
>>>  1 file changed, 30 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.c b/drivers/gpu/drm/nouveau/nouveau_acpi.c
>>> index df9f73e..e469df7 100644
>>> --- a/drivers/gpu/drm/nouveau/nouveau_acpi.c
>>> +++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c
>>> @@ -46,6 +46,7 @@ static struct nouveau_dsm_priv {
>>>  	bool dsm_detected;
>>>  	bool optimus_detected;
>>>  	bool optimus_flags_detected;
>>> +	bool optimus_skip_dsm;
>>>  	acpi_handle dhandle;
>>>  	acpi_handle rom_handle;
>>>  } nouveau_dsm_priv;
>>> @@ -212,8 +213,26 @@ static const struct vga_switcheroo_handler nouveau_dsm_handler = {
>>>  	.get_client_id = nouveau_dsm_get_client_id,
>>>  };
>>>
>>> +/* Firmware supporting Windows 8 or later do not use _DSM to put the device into
>>> + * D3cold, they instead rely on disabling power resources on the parent. */
>>> +static bool nouveau_pr3_present(struct pci_dev *pdev)
>>> +{
>>> +	struct pci_dev *parent_pdev = pci_upstream_bridge(pdev);
>>> +	struct acpi_device *ad;
>>
>> Nit: please call this adev instead of ad.
>
> Will do.
>
>>> +
>>> +	if (!parent_pdev)
>>> +		return false;
>>> +
>>> +	ad = ACPI_COMPANION(&parent_pdev->dev);
>>> +	if (!ad)
>>> +		return false;
>>> +
>>> +	return ad->power.flags.power_resources;
>>
>> Is this sufficient to tell if the parent device has _PR3? I thought it
>> returns true if it has power resources in general, not necessarily _PR3.
>>
>> Otherwise this looks okay to me.
>
> It is indeed set whenever there is any _PRx method. I wonder if it is
> appropriate to access fields directly like this, perhaps this would be
> more accurate (based on device_pm.c):
>
>     /* Check whether the _PR3 method is available. */
>     return adev->power.states[ACPI_STATE_D3_COLD].flags.valid;
>
> I am also considering adding a check in case the pcieport driver does
> not support D3cold via runtime PM, what do you think of this?
>
>     if (!parent_pdev)
>         return false;
>     /* If the PCIe port does not support D3cold via runtime PM, allow a
>      * fallback to the Optimus DSM method to put the device in D3cold. */
>     if (parent_pdev->no_d3cold)
>         return false;
>
> This is needed to avoid the regression reported in the cover letter, but
> also allows pre-2015 systems to (still) have the D3cold possibility.
>
>
> Out of curiosity I looked up an pre-2015 laptop (found Acer V5-573G,
> apparently from November 2013, Windows 8.1) and extracted the ACPI
> tables from the BIOS images. BIOS 2.28 (2014/05/13) introduces support
> for power resources on the parent devicea(\_SB.PCI0.PEG0._PR3 and a
> related NVP3 device) when _OSI("Windows 2013") is true. (This is added
> as alternative for the old DSM interface.)
>
> Maybe 2014 is also an appropriate cutoff date? I wonder if it is
> feasible to detect firmware use of _OSI("Windows 2013") and use that
> instead of the BIOS year.

It is definitely possible to check if the firmware uses _OSI("Windows 2013")
we do something similar to check for windows-8 ready laptops in the backlight
code, see acpi_osi_is_win8() in drivers/acpi/osl.c, or if you actually
want to test for Windows 8 or newer, just use acpi_osi_is_win8()  :)

Regards,

Hans