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+
+                Video issues with S3 resume
+                ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+                  2003-2005, Pavel Machek
+
+During S3 resume, hardware needs to be reinitialized. For most
+devices, this is easy, and kernel driver knows how to do
+it. Unfortunately there's one exception: video card. Those are usually
+initialized by BIOS, and kernel does not have enough information to
+boot video card. (Kernel usually does not even contain video card
+driver -- vesafb and vgacon are widely used).
+
+This is not problem for swsusp, because during swsusp resume, BIOS is
+run normally so video card is normally initialized. S3 has absolutely
+no chance of working with SMP/HT. Be sure it to turn it off before
+testing (swsusp should work ok, OTOH).
+
+There are a few types of systems where video works after S3 resume:
+
+(1) systems where video state is preserved over S3.
+
+(2) systems where it is possible to call the video BIOS during S3
+  resume. Unfortunately, it is not correct to call the video BIOS at
+  that point, but it happens to work on some machines. Use
+  acpi_sleep=s3_bios.
+
+(3) systems that initialize video card into vga text mode and where
+  the BIOS works well enough to be able to set video mode. Use
+  acpi_sleep=s3_mode on these.
+
+(4) on some systems s3_bios kicks video into text mode, and
+  acpi_sleep=s3_bios,s3_mode is needed.
+
+(5) radeon systems, where X can soft-boot your video card. You'll need
+  new enough X, and plain text console (no vesafb or radeonfb), see
+  http://www.doesi.gmxhome.de/linux/tm800s3/s3.html. Actually you
+  should probably use vbetool (6) instead.
+
+(6) other radeon systems, where vbetool is enough to bring system back
+  to life. It needs text console to be working. Do vbetool vbestate
+  save > /tmp/delme; echo 3 > /proc/acpi/sleep; vbetool post; vbetool
+  vbestate restore < /tmp/delme; setfont <whatever>, and your video
+  should work.
+
+(7) on some systems, it is possible to boot most of kernel, and then
+  POSTing bios works. Ole Rohne has patch to do just that at
+  http://dev.gentoo.org/~marineam/patch-radeonfb-2.6.11-rc2-mm2.
+
+Now, if you pass acpi_sleep=something, and it does not work with your
+bios, you'll get a hard crash during resume. Be careful. Also it is
+safest to do your experiments with plain old VGA console. The vesafb
+and radeonfb (etc) drivers have a tendency to crash the machine during
+resume.
+
+You may have a system where none of above works. At that point you
+either invent another ugly hack that works, or write proper driver for
+your video card (good luck getting docs :-(). Maybe suspending from X
+(proper X, knowing your hardware, not XF68_FBcon) might have better
+chance of working.
+
+Table of known working systems:
+
+Model                           hack (or "how to do it")
+------------------------------------------------------------------------------
+Acer Aspire 1406LC              ole's late BIOS init (7), turn off DRI
+Acer TM 242FX                   vbetool (6)
+Acer TM C300                    vga=normal (only suspend on console, not in X), vbetool (6)
+Acer TM 4052LCi                 s3_bios (2)
+Acer TM 636Lci                  s3_bios vga=normal (2)
+Acer TM 650 (Radeon M7)         vga=normal plus boot-radeon (5) gets text console back
+Acer TM 660                     ??? (*)
+Acer TM 800                     vga=normal, X patches, see webpage (5) or vbetool (6)
+Acer TM 803                     vga=normal, X patches, see webpage (5) or vbetool (6)
+Acer TM 803LCi                  vga=normal, vbetool (6)
+Arima W730a                     vbetool needed (6)
+Asus L2400D                     s3_mode (3)(***) (S1 also works OK)
+Asus L3800C (Radeon M7)         s3_bios (2) (S1 also works OK)
+Asus M6NE                       ??? (*)
+Athlon64 desktop prototype      s3_bios (2)
+Compal CL-50                    ??? (*)
+Compaq Armada E500 - P3-700     none (1) (S1 also works OK)
+Compaq Evo N620c                vga=normal, s3_bios (2)
+Dell 600m, ATI R250 Lf          none (1), but needs xorg-x11-6.8.1.902-1
+Dell D600, ATI RV250            vga=normal and X, or try vbestate (6)
+Dell Inspiron 4000              ??? (*)
+Dell Inspiron 500m              ??? (*)
+Dell Inspiron 600m              ??? (*)
+Dell Inspiron 8200              ??? (*)
+Dell Inspiron 8500              ??? (*)
+Dell Inspiron 8600              ??? (*)
+eMachines athlon64 machines     vbetool needed (6) (someone please get me model #s)
+HP NC6000                       s3_bios, may not use radeonfb (2); or vbetool (6)
+HP NX7000                       ??? (*)
+HP Pavilion ZD7000              vbetool post needed, need open-source nv driver for X
+HP Omnibook XE3 athlon version  none (1)
+HP Omnibook XE3GC               none (1), video is S3 Savage/IX-MV
+IBM TP T20, model 2647-44G      none (1), video is S3 Inc. 86C270-294 Savage/IX-MV, vesafb gets "interesting" but X work.
+IBM TP A31 / Type 2652-M5G      s3_mode (3) [works ok with BIOS 1.04 2002-08-23, but not at all with BIOS 1.11 2004-11-05 :-(]
+IBM TP R32 / Type 2658-MMG      none (1)
+IBM TP R40 2722B3G              ??? (*)
+IBM TP R50p / Type 1832-22U     s3_bios (2)
+IBM TP R51                      ??? (*)
+IBM TP T30      236681A         ??? (*)
+IBM TP T40 / Type 2373-MU4      none (1)
+IBM TP T40p                     none (1)
+IBM TP R40p                     s3_bios (2)
+IBM TP T41p                     s3_bios (2), switch to X after resume
+IBM TP T42                      ??? (*)
+IBM ThinkPad T42p (2373-GTG)    s3_bios (2)
+IBM TP X20                      ??? (*)
+IBM TP X30                      ??? (*)
+IBM TP X31 / Type 2672-XXH      none (1), use radeontool (http://fdd.com/software/radeon/) to turn off backlight.
+IBM Thinkpad X40 Type 2371-7JG  s3_bios,s3_mode (4)
+Medion MD4220                   ??? (*)
+Samsung P35                     vbetool needed (6)
+Sharp PC-AR10 (ATI rage)        none (1)
+Sony Vaio PCG-F403              ??? (*)
+Sony Vaio PCG-N505SN            ??? (*)
+Sony Vaio vgn-s260              X or boot-radeon can init it (5)
+Toshiba Libretto L5             none (1)
+Toshiba Satellite 4030CDT       s3_mode (3)
+Toshiba Satellite 4080XCDT      s3_mode (3)
+Toshiba Satellite 4090XCDT      ??? (*)
+Toshiba Satellite P10-554       s3_bios,s3_mode (4)(****)
+Uniwill 244IIO                  ??? (*)
+
+
+(*) from http://www.ubuntulinux.org/wiki/HoaryPMResults, not sure
+    which options to use. If you know, please tell me.
+
+(***) To be tested with a newer kernel.
+
+(****) Not with SMP kernel, UP only.
+
+VBEtool details
+~~~~~~~~~~~~~~~
+(with thanks to Carl-Daniel Hailfinger)
+
+First, boot into X and run the following script ONCE:
+#!/bin/bash
+statedir=/root/s3/state
+mkdir -p $statedir
+chvt 2
+sleep 1
+vbetool vbestate save >$statedir/vbe
+
+
+To suspend and resume properly, call the following script as root:
+#!/bin/bash
+statedir=/root/s3/state
+curcons=`fgconsole`
+fuser /dev/tty$curcons 2>/dev/null|xargs ps -o comm= -p|grep -q X && chvt 2
+cat /dev/vcsa >$statedir/vcsa
+sync
+echo 3 >/proc/acpi/sleep
+sync
+vbetool post
+vbetool vbestate restore <$statedir/vbe
+cat $statedir/vcsa >/dev/vcsa
+rckbd restart
+chvt $[curcons%6+1]
+chvt $curcons
+
+
+Unless you change your graphics card or other hardware configuration,
+the state once saved will be OK for every resume afterwards.
+NOTE: The "rckbd restart" command may be different for your
+distribution. Simply replace it with the command you would use to
+set the fonts on screen.