libreboot

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commit 7c71d042901d3f28fba31549f0942276261e1a6d
parent ffc88c45615ed5cdb0fc2df00de2d86f01d18bda
Author: Arthur Heymans <arthur@aheymans.xyz>
Date:   Tue, 28 Jun 2016 14:58:20 +0200

finetune backlight: add some newlines, clarify stuff

LED needs a higher PWM freq so lower devider.
Uneven backlight is more important to fix first when there is also
noise.
Makes it more clear that you want highest good value for devider,
which is equal to finding the lowest working frequency.

Diffstat:
docs/libreboot.texi | 17+++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

diff --git 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