diff options
Diffstat (limited to 'docs/i945_backlight.html')
| -rw-r--r-- | docs/i945_backlight.html | 118 |
1 files changed, 0 insertions, 118 deletions
diff --git a/docs/i945_backlight.html b/docs/i945_backlight.html deleted file mode 100644 index 1ce0137..0000000 --- a/docs/i945_backlight.html +++ /dev/null @@ -1,118 +0,0 @@ -<!DOCTYPE html> -<html lang="en"> -<head> - <meta charset="utf-8"> - <title>i945 backlight in libreboot</title> - - <style type="text/css"> - body { - font-family: sans-serif; - font-size: 1em; - background: #fff; - color: #000; - } - - </style> - - <meta name="viewport" content="width=device-width, initial-scale=1.0"> - <meta name="author" content="glugman"> - <meta name="description" content="tutorials for libreboot, the reboot library."> - <meta name="robots" content="all"> -</head> - -<body> - - <header> - <h1 id="pagetop">i945 backlight controls on X60/T60</h1> - </header> - - <p> - <a href="index.html">back to index</a> - </p> - -<hr/> - - <h2>Contents</h2> - <ul> - <li><a href="#x60_native_notes">X60 native graphics initialization (backlight controls)</a></li> - <li><a href="#t60_native_notes">T60 native graphics initialization (backlight controls)</a></li> - </ul> - -<hr/> - - <h1 id="x60_native_notes">X60 native graphics initialization (with backlight controls)</h1> - <p> - <b>The fix below was done on 5320/6 (review.coreboot.org) under src/mainboard/lenovo/x60/devicetree.cb</b> - </p> - <p> - Works on the ThinkPad X60, X60s and X60 Tablet. This change is also included by default in libreboot 6th release. - </p> - <p> - <b>Add backlight controls:</b> in <i>src/mainboard/lenovo/x60/devicetree.cb</i>, change <b>gpu_backlight</b> to <b>0x879F879E</b> - </p> - <p> - That's all! <b>This was also backported into libreboot 5th release (line 1233 in src/mainboard/lenovo/x60/i915io.c)</b>. GNUtoo (Denis Carikli) - told me about the register <b>BLC_PWM_CTL</b> and that you could set it to control backlight. I read that address using devmem2 while running the VBIOS:<br/> - <b># devmem2 0xe4361254 w</b> - </p> - <p> - When doing this, it gave back that value. The same trick was used to get backlight controls for T60 (see <a href="#t60_native_notes">#t60_native_notes</a>). - </p> - - <h2>Further notes (as of 6th libreboot release, initial revision)</h2> - <p> - Reading <b>0xe4361254</b> (address) in Lenovo BIOS always yields FFFFFFFF, even when writing to it (and writing to it doesn't affect brightness controls). - 'mtjm' on IRC found that the buttons (Fn keys) control /sys/class/backlight/acpi_video0 which has no affect on 61254 (BLC_PWM_CTL). He says - intel_backlight has different values and uses the register. devmem2 works, needs checking <b>lspci -vv</b> for where the memory is mapped, - which is different than on coreboot; mtjm found that it was 0xec061254 on his machine (X60 Tablet), and the register value is different too. - <b>This is relevant, because we still don't know how backlight controls are actually handled. We got it working by accident. We need to know more.</b>. - </p> - <p> - Intel-gpu-tools may prove useful for further debugging: <a href="http://cgit.freedesktop.org/xorg/app/intel-gpu-tools/">http://cgit.freedesktop.org/xorg/app/intel-gpu-tools/</a> - </p> - <p> - mtjm says 0xe4300000 is an MMIO region of the gpu (lspci -vv shows it), 0x61254 (BLC_PWM_CTL) is a documented register. Searching the kernel driver for backlight - shows that in intel_panel.c this register is used (there is an XXX comment about finding the right value, where recent kernels get it from. - </p> - <p> - What we want to do is calculate a good value, instead of setting it in devicetree.cb. mtjm says about backlight physics: - it has a light source , uses pulse width modulation (PWM) to turn it on/off, dimming is done by spending less time on. - <b>Note: this may not be correct; he says his understanding is based on how the Lenote yeeloong works</b>. - </p> - <p> - mtjm goes on to say, that the register specifies the frequency used for PWM in its depending on the GPU core frequency, so it - might be possible to calculate it without hardcoded laptop-specific values. Therefore, I am supposed to find out the 'display core frequency' - (mtjm says there might be a register for it; also, it might be in 5320 or the replay code) and the PWM modulation frequency. - https://en.wikipedia.org/wiki/Backlight#Flicker_due_to_backlight_dimming - </p> - <p> - phcoder (Vladimir Serbinenko) who is author of 5320 (review.coreboot.org) talks about 'duty cycle limit' and 'flickering frequency'. - </p> - - <p><a href="#pagetop">Back to top of page</a></p> - -<hr/> - - <h1 id="t60_native_notes">T60 native graphics initialization (with backlight controls)</h1> - <p> - <b>The fix below was done on an earlier version of 5345 (review.coreboot.org) cherry-picked on top of 5320 checkout, but also works on the current version.</b> - </p> - <p> - This change is also included by default in libreboot 6th release. - </p> - <p> - <b>Add backlight controls:</b> in <i>src/mainboard/lenovo/t60/devicetree.cb</i>, change <b>gpu_backlight</b> to <b>0x58BF58BE</b> - </p> - - <p><a href="#pagetop">Back to top of page</a></p> - -<hr/> - - <p> - Copyright © 2014 Francis Rowe, All Rights Reserved.<br/> - See <a href="license.html">license.html</a> for license conditions. - </p> - -</body> -</html> - |