amdgpu panic: Offset 00000000 out of framebuffer size on Strix [Radeon 880M / 890M] #408
Description
Describe the bug
System panics immediately after kldload amgpu
FreeBSD version
FreeBSD AI300 16.0-CURRENT FreeBSD 16.0-CURRENT #7 n283918-87f5b3153f15-dirty: Thu Jan 29 09:12:12 EST 2026 user@AI300:/home/user/obj/home/user/freebsd/amd64.amd64/sys/GENERIC amd64 1600011 1600004
This is my WIP tree on top of commit 783b8a0fd880255a8315db7f59d0450bd7276f4d
PCI Info
vgapci0@pci0:193:0:0: class=0x038000 rev=0xc1 hdr=0x00 vendor=0x1002 device=0x150e subvendor=0xf111 subdevice=0x000d
vendor = 'Advanced Micro Devices, Inc. [AMD/ATI]'
device = 'Strix [Radeon 880M / 890M]'
class = display
DRM KMOD version
commit 18debec29a6f2f84c8f72b87b22d704648dd3aa7 (origin/master, origin/HEAD)
Author: Ed Maste <emaste@FreeBSD.org>
Date: Mon Nov 24 21:48:16 2025 -0500
drm/amd/display: Protect FPU in dml2_init() and dml2_validate()
Part of Linux commits afcdf51d97cd58dd7a2e0aa8acbaea5108fa6826 and
366e77cd4923c3aa45341e15dcaf3377af9b042f by Huacai Chenl
<chenhuacai@kernel.org>.
Fixes #372.
To Reproduce
kldload amdgpu
Screenshots
Additional context
In struct linux_fb_info *info, info->screen_base and info->screen_size are both 0.
Adding the hack shown below to fb_setpixel() avoids the panic but as is clear from the patch results in a nonfunctional console. Nonetheless it is possible to start X (as in https://mastodon.social/@emaste/115667720362871745).
diff --git a/drivers/gpu/drm/linux_fb.c b/drivers/gpu/drm/linux_fb.c
index 2aad76ab15..a76fa7b107 100644
--- a/drivers/gpu/drm/linux_fb.c
+++ b/drivers/gpu/drm/linux_fb.c
@@ -334,6 +334,10 @@ fb_setpixel(struct linux_fb_info *info, uint32_t x, uint32_t y,
uint32_t bytes_per_pixel;
unsigned int offset;
+ /* amdgpu does not populate these */
+ if (info->screen_base == 0 || info->screen_size == 0)
+ return;
+
bytes_per_pixel = info->var.bits_per_pixel / 8;
offset = info->fix.line_length * y + x * bytes_per_pixel;