Ubuntu – Ubuntu freezes after resume from suspend/hibernate in 10-15 sec

Simply put, you can't use nouveau that do not support putting the NVidia vga adapter in suspend and expect that suspend works. I'm sorry, you have to install the proprietary NVidia drivers to make suspend work again... see this: nouveau driver prevents suspending, and I wouldn't even need it

The solution was ultimately found posted on Sept 18th on the Dell Community Forums. This is ultimately a bios problem: during suspend, an intel register is reset to all 0's. A kernel patch workaround is already in the works, but may not be included until 4.9. However, the register can be saved to a file during suspend and loaded during resume.

Save the following script as /lib/systemd/system-sleep/fixbacklight (and chmod 755)

#!/bin/sh
# From patchwork.freedesktop.org/.../
# and en.community.dell.com/.../19985320
# Suspend Resume fails to restore PWM_GRANUALITY
# Based on script by Tony.Jewell@Cregganna.Com

INTEL_REG=/usr/bin/intel_reg
ADDR="0x000c2000"
SAVE_FILE=/var/lib/systemd/save_intel_reg_pwm_granuality

[ -x "$INTEL_REG" ] || exit 0

case "$1" in
    pre)
        echo "$0: Saving Intel Register PWM_GRANUALITY"
        "$INTEL_REG" read "$ADDR" \
            | (read addr value && echo "$value") \
            >"$SAVE_FILE"
    sync
    ;;
    post)
        value=`cat "$SAVE_FILE" 2>/dev/null`
        if [ -n "$value" ]
        then
            echo "$0: Restoring Intel Register PWM_GRANUALITY $value"
            "$INTEL_REG" write "$ADDR" "$value"
            rm "$SAVE_FILE"
        fi
    ;;
esac

It was @nloewen that pointed me down the right path.