function: get current DP PHY settings: voltage swing, pre-emphasis, post-cursor2 (defined by VESA DP specification) valid values: voltage swing: 0,1,2,3 pre-emphasis : 0,1,2,3 post cursor2 : 0,1,2,3 debugfs file phy_setings is located at /sys/kernel/debug/dri/0/DP-x there will be directories, like DP-1, DP-2,DP-3, etc. for DP display --- to figure out which DP-x is the display for DP to be check, cd DP-x ls -ll There should be debugfs file, like link_settings, phy_settings. cat link_settings from lane_count, link_rate to figure which DP-x is for display to be worked on --- to get current DP PHY settings, cat phy_settings --- to change DP PHY settings, echo <voltage_swing> <pre-emphasis> <post_cursor2> > phy_settings for examle, to change voltage swing to 2, pre-emphasis to 3, post_cursor2 to 0, echo 2 3 0 > phy_settings --- to check if change be applied, get current phy settings by cat phy_settings --- in case invalid values are set by user, like echo 1 4 0 > phy_settings HW will NOT be programmed by these settings. cat phy_settings will show the previous valid settings. Signed-off-by: Hersen Wu <hersenxs.wu@amd.com> Reviewed-by: Harry Wentland <Harry.Wentland@amd.com> Reviewed-by: Hersen Wu <hersenxs.wu@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>