Acer VN7-592g

Date: 2016-04-16 01:32 pm (UTC)
From: (Anonymous)
I did some more experiments regarding reasons preventing my laptop from entering deep PC modes. I am attaching some notes, hope this may help others when debugging why their SKLs fail to enter deeper PC states.

Kernel: 4.6.0rc3 (4.5 fails to work)

After start: Enters only PC2
After first suspend: Goes to PC3 max (don't know why yet - firmware must be changing some configuration)

Factors discovered preventing entering deeper PC:

1. Kernel version - 4.6 kernel is needed
2. r8169 module for:

08:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 15)

Replaced with r8168 and works flawlessly.

3. pcie_aspm=force kernel parameter is needed (by default kernel won't enable ASPM - this is needed)

4. NVIDIA Optimus: We need to first load nouveau driver, then disable the card using bbswitch (optional). If no driver is loaded (or nvidia proprietary one), then it fails to enter deeper PC states.

I use:
modprobe nouveau
sleep 1
echo OFF > /proc/acpi/bbswitch

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Matthew Garrett

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Power management, mobile and firmware developer on Linux. Security developer at Google. Ex-biologist. @mjg59 on Twitter. Content here should not be interpreted as the opinion of my employer.

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