On Wed, Jun 01, 2016 at 06:51:51PM +0200, Peter Wu wrote:
On Tue, May 31, 2016 at 02:20:26PM +0200, Lukas Wunner wrote:
On Mon, May 30, 2016 at 06:13:51PM +0200, Peter Wu wrote:
Do you have any suggestions for the case where the pcieport driver refuses to put the bridge in D3 (because the BIOS is too old)? In that case the nouveau driver needs to fallback to the DSM method (but not when runtime PM is deliberately disabled by writing control=on).
The BIOS cut-off date is meant to avoid issues when suspending ports on older chipsets. However if the port is used for an Optimus GPU and we can clearly identify that, and there's a _PR3 method provided, it's probably safe to say that the port is *intended* to be suspended.
So you may want to consider amending pci_bridge_d3_possible() to allow D3 for such ports regardless of the BIOS date, as I've done for Thunderbolt in this commit: https://github.com/l1k/linux/commit/3cb8549cd4e5
Then we have heuristics based on BIOS year, on whether it is TB or not, and next to it whether it is an Optimus laptop? Maybe the PCI core needs to export a function that allows drivers to override the detection if this becomes more common.
Well I consider the TB and Optimus whitelisting as a stop-gap until the BIOS date is lowered. Rafael wrote:
Some time around when machines with Windows 10 started to ship should be relatively safe. I guess we can just pick a reasonable date in the initial patch and then try to move it back to the past subsequently and see if that breaks things for anyone.
Source: http://permalink.gmane.org/gmane.linux.power-management.general/75133
Not sure how to uniquely identify such ports though. Perhaps check if there's a device in slot 0 below the port which has (pdev->class >> 16) == PCI_BASE_CLASS_DISPLAY && (pdev->vendor == PCI_VENDOR_ID_NVIDIA || pdev->vendor == PCI_VENDOR_ID_ATI)
Seems fragile, there are desktop setups satisfying this match.
Of course, I didn't mean this to be used as is, you'd have to augment this with checks e.g. for presence of _PR3 and (if possible) Optimus, but I'm not familiar enough with Optimus to write down working code for it, I'm only familiar with apple-gmux switching.
Best regards,
Lukas