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| -rw-r--r-- | docs/libreboot.texi | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/docs/libreboot.texi b/docs/libreboot.texi index 3b40dab..db12bce 100644 --- a/docs/libreboot.texi +++ b/docs/libreboot.texi @@ -7617,29 +7617,30 @@ The tool for setting registry values on intel gpu's is included in intel-gpu-too You can set values: @* @strong{sudo intel_reg write 0x00061254 <your_value>} -The value set has the following structure: -bits [31:16] is PWM divider. PWM / PWM_divider = frequency +The value set has the following structure: @* +bits [31:16] is PWM divider. PWM / PWM_divider = frequency @* bits [15:0] is the duty cycle and determines the portion of the backlight modulation frequency. A value of 0 will mean that the display is off. A value equal to the backlight modulation frequency means full on. The value should not be larger than the backlight modulation frequency. On displays with a CCFL backlight start from: @strong{0x60016001} To verify if all modes work as desired use: @* @strong{xbacklight -set 10} @* -and gradually increase until 100. -Displays with an LED backlight need a lower backlight modulation. Do the same thing but start from +and gradually increase until 100. @* +Displays with a LED backlight need a higher PWM frequency. Do the same thing but start from @strong{0x01290129} . Try setting different values until you have found a value which presents no issue. It is important to know that there are four failure modes: @* 1. flickering very fast, which could cause epilepsy (frequency is too low. decrease divider) -@* 2. randomly flickering in random intervals - driver IC cannot keep up with toggling the mosfet (frequency too fast, increase divider) -@* 3. frequency is in audible range and causes coils to whine (frequency is too high. increase divider) -@* 4. backlight is uneven. (CCFL specific, frequency is too high. increase divider) +@* 2. randomly flickering in random intervals - driver IC cannot keep up with toggling the mosfet (frequency too high, increase divider) +@* 3. backlight is uneven. (CCFL specific, frequency is too high. increase divider) +@* 4. frequency is in audible range and causes coils to whine (frequency is too low. decrease divider) + To check for flickering try moving your laptop while looking at it. -A higher frequency equals higher power consumption. You want to find the highest good working value. +A higher frequency equals higher power consumption. You want to find the highest good working value for the devider (lowest frequency). Next this value should be set at boot: either add |