[Bug 102646] Screen flickering under amdgpu-experimental [buggy auto power profile]

[bugzilla-daemon@freedesktop.org]

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https://bugs.freedesktop.org/show_bug.cgi?id=102646

George Scorer <georgescorer@yahoo.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|high                        |low
           Severity|major                       |minor

--- Comment #70 from George Scorer <georgescorer@yahoo.co.uk> ---
Building on julien tempel's workaround, here's a somewhat more complex script
to manage the memory p-state jumps. It switches between low and high memory
p-states very reluctantly, so minimizing instances of flickering. I'm not a
bash expert so please excuse the clumsy coding, but this works for me.

#!/bin/bash

# Each memory p-state switch causes a screen flicker. Tweak these variables to
match
# your personal 'flicker aversion' vs efficiency trade-off.
CORE_P_STATE_UP=6    # The gpu core p-state at which we should jump up to
memory p-state 2
CORE_P_STATE_DOWN=1  # The gpu core p-state at which we should drop down to low
memory p-state
UP_DELAY=2           # in seconds. How long to stay in low memory p-state
before checking whether we can jump up to 2.
DOWN_DELAY=10        # in seconds. How long to stay in memory p-state 2 before
checking whether we can drop down to low.
SLEEP_INTERVAL=1     # in seconds. How frequently we should poll the core
p-state.
LOW_MEM_STATE=0      # Choose between 0 & 1

# Sysfs paths here are hardcoded for one amdgpu card at card0; adjust as
needed.
FILE_PERF_LEVEL=/sys/class/drm/card0/device/power_dpm_force_performance_level
FILE_MEM_P_STATE=/sys/class/drm/card0/device/pp_dpm_mclk
FILE_CORE_P_STATE=/sys/class/drm/card0/device/pp_dpm_sclk


# check for root privileges
if [ $UID -ne 0 ]
then
  echo "Writing to sysfs requires root privileges; relaunch as root"
  exit 1
fi

# Set gpu performance level control to manual
# echo "Setting performance level control to manual"
echo "manual" > "$FILE_PERF_LEVEL"

# Read the current core p-state and set a corresponding initial memory p-state

CORE_P_STATE="$(grep -F '*' $FILE_CORE_P_STATE)"
CORE_P_STATE=${CORE_P_STATE:0:1}

if [ "$CORE_P_STATE" -ge "$CORE_P_STATE_UP" ]; then
  MEM_P_STATE=2
else
  MEM_P_STATE=$LOW_MEM_STATE
fi

echo "$MEM_P_STATE" > "$FILE_MEM_P_STATE"
PROPOSED_MEM_P_STATE=$MEM_P_STATE

function check_core_p_state {

  CORE_P_STATE="$(grep -F '*' $FILE_CORE_P_STATE)"
  CORE_P_STATE=${CORE_P_STATE:0:1}

# Propose what the corresponding memory p-state should be
  OLD_PROPOSED_MEM_P_STATE=$PROPOSED_MEM_P_STATE
  PROPOSED_MEM_P_STATE=$MEM_P_STATE
  if [ "$CORE_P_STATE" -ge "$CORE_P_STATE_UP" ]; then
    PROPOSED_MEM_P_STATE=2
  elif [ "$CORE_P_STATE" -le "$CORE_P_STATE_DOWN" ]; then
    PROPOSED_MEM_P_STATE=$LOW_MEM_STATE
  fi

  if [ "$PROPOSED_MEM_P_STATE" -ne "$MEM_P_STATE" ]; then
#   We want to change so determine where we are in the countdown.    
    if [ "$PROPOSED_MEM_P_STATE" -ne "$OLD_PROPOSED_MEM_P_STATE" ]; then
      if [ "$PROPOSED_MEM_P_STATE" -eq 2 ]; then
        CHANGE_COUNTDOWN=$UP_DELAY
      else
        CHANGE_COUNTDOWN=$DOWN_DELAY
      fi
    fi
    (( CHANGE_COUNTDOWN = $CHANGE_COUNTDOWN - $SLEEP_INTERVAL ))

    if [ $CHANGE_COUNTDOWN -le 0 ]; then
#   The countdown has reached 0 so change the memory p-state.
      MEM_P_STATE=$PROPOSED_MEM_P_STATE
      echo "$MEM_P_STATE" > "$FILE_MEM_P_STATE"
    fi
#  else
#   we don't want to change.  
  fi

#    echo "Old  Prop  Mem  Core  Countdown"
#    echo "  $OLD_PROPOSED_MEM_P_STATE     $PROPOSED_MEM_P_STATE   
$MEM_P_STATE     $CORE_P_STATE         $CHANGE_COUNTDOWN"
#    echo ""
}

function reset_on_fail {
  echo "Exiting, setting memory p-state to 2"
  echo "manual" > "$FILE_PERF_LEVEL"
  echo "2" > "$FILE_MEM_P_STATE"
  exit 1
}

# always try to fix memory p-state 2 on failure
trap "reset_on_fail" SIGINT SIGTERM

function run_daemon {
  while :; do
    sleep $SLEEP_INTERVAL
    check_core_p_state
  done
}

# start the loop

run_daemon

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