Re: port-macppc/59529: POWERMAC_G5 trap setting color palette

["Michael via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR port-macppc/59529; it has been noted by GNATS.

From: Michael <macallan1888%gmail.com@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: port-macppc/59529: POWERMAC_G5 trap setting color palette
Date: Mon, 21 Jul 2025 07:15:48 -0400

 Hello,
 
 On Thu, 17 Jul 2025 19:00:01 +0000 (UTC)
 gson%gson.org@localhost (Andreas Gustafsson) wrote:
 
 > If I try to boot the POWERMAC_G5 kernel on a Power Mac G5 model A1093,
 > it gets as far as attaching genfb, but immediately after the screen
 > switches from the small Open Firmware font and white background to
 > the larger wscons font and a black background, it gets into a loop
 > printing two lines like these over and over:
 > 
 >   [    1.0000000] trap: kernel read DSI trap @ 0x8070200c by 0xff848714 (DSISR 0x40000000, err=14), lr 0xff87a524
 >   [    1.0000000] Press a key to panic
 
 I've seen this on newer, PCIe-based G5 models, we call OF_quiesce() to
 shut down background tasks so we can have full control over the
 hardware, but after that certain OF calls crash. IIRC rin@ committed a
 workaround a while ago, no idea if it made it into 10.
 
 There are a few things to check:
 - please try a -current kernel
 - try a -current kernel with gffb enabled. This will avoid the OF calls
   and program palette registers directly
 
 The problem with gffb is, I only tested it with the hardware I have,
 currently that's geforce mx2, 6800U, FX 5200 Go and FX 5200U. The
 latter is fairly common in lower end G5s, I added support for it today.
 The Go variant was used in iMacs and PowerBooks.
 
 That being said, your G5 is a PowerMac9,1  a variant I don't have, so
 the fan control code may not be fully functional. Please send me:
 - dmesg output
 - ofctl -p output
 so I can fix that.
 
 envstat should list 6 or 7 fans and about 6 temperature sensors. If
 yours shows less please be careful. The CPU has a huge heat sink so
 overheating it will take a while under full load even with all fans
 stopped ( which is unlikely to happen - OF will spin them up and if we
 don't find the fans or temperature sensors we leave them alone ). 
 
 have fun
 Michael