Hi,

On Thu, Feb 8, 2018 at 2:28 PM, Bartlomiej Zolnierkiewicz
[off-list ref] wrote:

On Wednesday, January 31, 2018 08:51:23 PM Mathieu Malaterre wrote:

quoted

Bartlomiej,

On Wed, Jan 31, 2018 at 12:57 PM, Bartlomiej Zolnierkiewicz
[off-list ref] wrote:

quoted

On Tuesday, January 30, 2018 02:14:10 PM Mathieu Malaterre wrote:

quoted

Bartlomiej,

On Wed, Jan 3, 2018 at 3:47 PM, Bartlomiej Zolnierkiewicz
[off-list ref] wrote:

quoted

On Thursday, December 21, 2017 11:07:56 PM Mathieu Malaterre wrote:

quoted

When the linux kernel is build with (typical kernel ship with Debian
installer):

CONFIG_FB_OF=y
CONFIG_VT_HW_CONSOLE_BINDING=y
CONFIG_FB_RADEON=m

The offb driver takes precedence over module radeonfb. It is then
impossible to load the module, error reported is:

[   96.551486] radeonfb 0000:00:10.0: enabling device (0006 -> 0007)
[   96.551526] radeonfb 0000:00:10.0: BAR 0: can't reserve [mem 0x98000000-0x9fffffff pref]
[   96.551531] radeonfb (0000:00:10.0): cannot request region 0.
[   96.551545] radeonfb: probe of 0000:00:10.0 failed with error -16

This patch reproduce the behavior of the module radeon, so as to make it
possible to load radeonfb when offb is first loaded.

It should be noticed that `offb_destroy` is never called which explain the
need to skip error detection on the radeon side.

This still needs to be explained more, from my last mail:

"The last put_fb_info() on fb_info should call ->fb_destroy
(offb_destroy in our case) and remove_conflicting_framebuffers()
is calling put_fb_info() so there is some extra reference on
fb_info somewhere preventing it from going away.

Please look into fixing this."

I am not familiar with the fb stuff internals but here is what I see:

# modprobe radeonfb

leads to:

[   52.058546] bus: 'pci': add driver radeonfb
[   52.058588] bus: 'pci': driver_probe_device: matched device
0000:00:10.0 with driver radeonfb
[   52.058595] bus: 'pci': really_probe: probing driver radeonfb with
device 0000:00:10.0
[   52.058608] devices_kset: Moving 0000:00:10.0 to end of list
[   52.058613] radeonfb_pci_register BEGIN
[   52.058634] radeonfb 0000:00:10.0: enabling device (0006 -> 0007)
<at this point radeon_kick_out_firmware_fb is called>
[   52.058666] checking generic (9c008000 96000) vs hw (98000000 8000000)
[   52.058667] fb: switching to radeonfb from OFfb ATY,RockHo
[   52.058844] Console: switching to colour dummy device 80x25
[   52.058860] device: 'fb0': device_unregister
[   52.058956] PM: Removing info for No Bus:fb0
[   52.059014] device: 'fb0': device_create_release
<a call to do_unregister_framebuffer is done>
<put_fb_info is done with a count=2 and dev=NULL>
[   52.059048] device: 'vtcon1': device_unregister
[   52.059076] PM: Removing info for No Bus:vtcon1
[   52.059091] device: 'vtcon1': device_create_release
[   52.059107] radeonfb 0000:00:10.0: BAR 0: can't reserve [mem
0x98000000-0x9fffffff pref]
[   52.256151] aper_base: 98000000 MC_FB_LOC to: 9bff9800, MC_AGP_LOC
to: ffffa000
[   52.256157] radeonfb (0000:00:10.0): Found 32768k of DDR 64 bits
wide videoram

I can confirm that offb_destroy is never called (not sure exactly
why), but in any case the call to radeon_kick_out_firmware_fb happen
much earlier, at least before the put_fb_info.

It is okay, put_fb_info() is called indirectly by radeon_kick_out_firmware_fb()

radeon_kick_out_firmware_fb()
        remove_conflicting_framebuffers()
                do_remove_conflicting_framebuffers()
                        do_unregister_framebuffer()
                                put_fb_info()

offb_destroy() is not called because there is an extra reference on old
fb_info (->count == 2):

static void put_fb_info(struct fb_info *fb_info)
{
        if (!atomic_dec_and_test(&fb_info->count))
                return;
        if (fb_info->fbops->fb_destroy)
                fb_info->fbops->fb_destroy(fb_info);
}

The question is why there is an extra reference, probably user-space
is still holding the fb_info reference obtained in fb_open() call and
fb_release() is never called. Besides not calling fbops->fb_destroy()
this also causes missing call of fbops->fb_release() (in fb_release())
which some fb drivers are implementing (but not offb.c).

quoted

Could you describe a bit more the chain of calls you were thinking of ?

Please add WARN_ON(1) to get_fb_info() and put_fb_info() so we can check
from the stacktrace if it is actually fb_open() that holds the extra
old fb_info reference.

drivers/video/fbdev/core/fbmem.c:

static struct fb_info *get_fb_info(unsigned int idx)
{
        struct fb_info *fb_info;

        if (idx >= FB_MAX)
                return ERR_PTR(-ENODEV);

        mutex_lock(&registration_lock);
        fb_info = registered_fb[idx];
        if (fb_info)
                atomic_inc(&fb_info->count);

if (fb_info)
        WARN_ON(1);

        mutex_unlock(&registration_lock);

        return fb_info;
}

static void put_fb_info(struct fb_info *fb_info)
{
WARN_ON(1);

        if (!atomic_dec_and_test(&fb_info->count))
                return;
        if (fb_info->fbops->fb_destroy)
                fb_info->fbops->fb_destroy(fb_info);
}

Alright, here is what I see:

[   18.961639] PM: Adding info for No Bus:vcs7
[   18.966448] device: 'vcsa7': device_add
[   18.966496] PM: Adding info for No Bus:vcsa7
[   19.001701] WARNING: CPU: 0 PID: 405 at
drivers/video/fbdev/core/fbmem.c:68 get_fb_info.part.3+0x58/0x7c
[   19.001715] Modules linked in: uinput snd_aoa_codec_toonie
snd_aoa_fabric_layout snd_aoa snd_aoa_i2sbus snd_aoa_soundbus snd_pcm
snd_timer snd soundcore rack_meter evdev i2c_dev sg usb_storage
ip_tables x_tables autofs4 ext4 crc16 mbcache jbd2 fscrypto
hid_generic usbhid hid ohci_pci ehci_pci ohci_hcd ehci_hcd sungem
firewire_ohci sungem_phy sr_mod firewire_core crc_itu_t cdrom sd_mod
usbcore
[   19.001773] CPU: 0 PID: 405 Comm: Xorg Not tainted 4.15.0+ #321
[   19.001778] NIP:  c039ef20 LR: c039eefc CTR: c039ef44
[   19.001781] REGS: decc7c80 TRAP: 0700   Not tainted  (4.15.0+)
[   19.001784] MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 28222828  XER: 00000000
[   19.001795]
               GPR00: c039eefc decc7d30 c147ab00 00000000 dc3ed8c0
df568a6c 00000001 c147ab00
               GPR08: df568a6c 00000002 00000000 dc280c50 28222822
006f9ff4 006fff50 80000000
               GPR16: 88000228 00000008 bfcb5b08 00000002 decc7e60
80000000 ffffffea 00000041
               GPR24: 00000000 00000006 df568a6c dc3ed8c0 df5ef1e8
df568a40 c08f7c18 dc198800
[   19.001835] NIP [c039ef20] get_fb_info.part.3+0x58/0x7c
[   19.001840] LR [c039eefc] get_fb_info.part.3+0x34/0x7c
[   19.001842] Call Trace:
[   19.001848] [decc7d30] [c039eefc] get_fb_info.part.3+0x34/0x7c (unreliable)
[   19.001854] [decc7d40] [c039efa0] fb_open+0x5c/0x18c
[   19.001866] [decc7d60] [c01e0e90] chrdev_open+0xb8/0x19c
[   19.001872] [decc7d90] [c01d7994] do_dentry_open+0x24c/0x398
[   19.001881] [decc7dc0] [c01ec378] path_openat+0x4c4/0x11b8
[   19.001888] [decc7e50] [c01ee0d8] do_filp_open+0xbc/0x10c
[   19.001893] [decc7f00] [c01d93b0] do_sys_open+0x158/0x228
[   19.001901] [decc7f40] [c00181cc] ret_from_syscall+0x0/0x40
[   19.001908] --- interrupt: c01 at 0xb751b940
                   LR = 0xb751b8dc
[   19.001912] Instruction dump:
[   19.001917] 7fc3f378 57ff103a 482cc171 3d20c093 39291a84 7fe9f82e
2f9f0000 419e0018
[   19.001927] 7d20f828 31290001 7d20f92d 40a2fff4 <0fe00000> 7fc3f378
482cca69 7fe3fb78
[   19.001938] ---[ end trace e0bf4192eb1c4f60 ]---
[   19.001985] WARNING: CPU: 0 PID: 405 at
drivers/video/fbdev/core/fbmem.c:77 put_fb_info+0x18/0x68
[   19.001988] Modules linked in: uinput snd_aoa_codec_toonie
snd_aoa_fabric_layout snd_aoa snd_aoa_i2sbus snd_aoa_soundbus snd_pcm
snd_timer snd soundcore rack_meter evdev i2c_dev sg usb_storage
ip_tables x_tables autofs4 ext4 crc16 mbcache jbd2 fscrypto
hid_generic usbhid hid ohci_pci ehci_pci ohci_hcd ehci_hcd sungem
firewire_ohci sungem_phy sr_mod firewire_core crc_itu_t cdrom sd_mod
usbcore
[   19.002028] CPU: 0 PID: 405 Comm: Xorg Tainted: G        W
4.15.0+ #321
[   19.002031] NIP:  c039e6ec LR: c039eeb0 CTR: c039ee48
[   19.002035] REGS: decc7e10 TRAP: 0700   Tainted: G        W         (4.15.0+)
[   19.002037] MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 28000222  XER: 20000000
[   19.002047]
               GPR00: c039eeb0 decc7ec0 c147ab00 dc198800 dc3ed8c0
dc3ed8c8 00000001 c147ab00
               GPR08: 00000000 c08fa6f8 00000000 dc280c50 28000228
006f9ff4 006fff50 00000000
               GPR16: 007001a8 00000008 bfcb5b08 007001a4 00000000
0070d0c4 00000002 00000000
               GPR24: b6ad8b1c dc3ed8c8 df5ef1e8 df3e4ee0 dc280c50
df5ef1e8 dc19880c dc198800
[   19.002086] NIP [c039e6ec] put_fb_info+0x18/0x68
[   19.002091] LR [c039eeb0] fb_release+0x68/0x80
[   19.002093] Call Trace:
[   19.002096] [decc7ec0] [df5ef1e8] 0xdf5ef1e8 (unreliable)
[   19.002102] [decc7ed0] [c039eeb0] fb_release+0x68/0x80
[   19.002108] [decc7ee0] [c01dd2e8] __fput+0xb4/0x260
[   19.002118] [decc7f10] [c006e088] task_work_run+0xc0/0xe8
[   19.002129] [decc7f30] [c000aa90] do_notify_resume+0xb4/0xb8
[   19.002135] [decc7f40] [c0018b4c] do_user_signal+0x7c/0xcc
[   19.002140] --- interrupt: c00 at 0xb751a7d8
                   LR = 0xb751a7ac
[   19.002144] Instruction dump:
[   19.002147] 80010014 38210010 7c0803a6 4e800020 38600000 4e800020
7c0802a6 90010004
[   19.002157] 60000000 9421fff0 7c0802a6 90010014 <0fe00000> 7d401828
314affff 7d40192d
[   19.002168] ---[ end trace e0bf4192eb1c4f61 ]---
[   19.002595] WARNING: CPU: 0 PID: 405 at
drivers/video/fbdev/core/fbmem.c:68 get_fb_info.part.3+0x58/0x7c
[   19.002601] Modules linked in: uinput snd_aoa_codec_toonie
snd_aoa_fabric_layout snd_aoa snd_aoa_i2sbus snd_aoa_soundbus snd_pcm
snd_timer snd soundcore rack_meter evdev i2c_dev sg usb_storage
ip_tables x_tables autofs4 ext4 crc16 mbcache jbd2 fscrypto
hid_generic usbhid hid ohci_pci ehci_pci ohci_hcd ehci_hcd sungem
firewire_ohci sungem_phy sr_mod firewire_core crc_itu_t cdrom sd_mod
usbcore
[   19.002645] CPU: 0 PID: 405 Comm: Xorg Tainted: G        W
4.15.0+ #321
[   19.002649] NIP:  c039ef20 LR: c039eefc CTR: c039ef44
[   19.002652] REGS: decc7c80 TRAP: 0700   Tainted: G        W         (4.15.0+)
[   19.002655] MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 28222248  XER: 00000000
[   19.002664]
               GPR00: c039eefc decc7d30 c147ab00 00000000 deca0340
deca0348 00000001 00000000
               GPR08: 00000000 00000002 00000000 dc280c50 28222842
006f9ff4 006fff50 80000000
               GPR16: 88000448 00000001 00000000 00000002 decc7e60
80000000 ffffffea 00000041
               GPR24: 00000000 00000006 c01e0dd8 deca0340 df5ef1e8
df568a40 c08f7c18 dc198800
[   19.002704] NIP [c039ef20] get_fb_info.part.3+0x58/0x7c
[   19.002708] LR [c039eefc] get_fb_info.part.3+0x34/0x7c
[   19.002711] Call Trace:
[   19.002716] [decc7d30] [c039eefc] get_fb_info.part.3+0x34/0x7c (unreliable)
[   19.002722] [decc7d40] [c039efa0] fb_open+0x5c/0x18c
[   19.002730] [decc7d60] [c01e0e90] chrdev_open+0xb8/0x19c
[   19.002735] [decc7d90] [c01d7994] do_dentry_open+0x24c/0x398
[   19.002743] [decc7dc0] [c01ec378] path_openat+0x4c4/0x11b8
[   19.002748] [decc7e50] [c01ee0d8] do_filp_open+0xbc/0x10c
[   19.002754] [decc7f00] [c01d93b0] do_sys_open+0x158/0x228
[   19.002760] [decc7f40] [c00181cc] ret_from_syscall+0x0/0x40
[   19.002766] --- interrupt: c01 at 0xb751b940
                   LR = 0xb751b8dc
[   19.002770] Instruction dump:
[   19.002774] 7fc3f378 57ff103a 482cc171 3d20c093 39291a84 7fe9f82e
2f9f0000 419e0018
[   19.002784] 7d20f828 31290001 7d20f92d 40a2fff4 <0fe00000> 7fc3f378
482cca69 7fe3fb78
[   19.002795] ---[ end trace e0bf4192eb1c4f62 ]---
[   19.011629] gem 0002:20:0f.0 eth0: Link is up at 100 Mbps, full-duplex
[   19.011746] gem 0002:20:0f.0 eth0: Pause is disabled
[   19.011846] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[   19.018954] device: 'input3': device_add
[   19.019031] PM: Adding info for No Bus:input3


Then later on (after modprobe radeonfb):

[  657.135105] PM: Removing info for No Bus:fb0
[  657.135164] device: 'fb0': device_create_release
[  657.135279] WARNING: CPU: 0 PID: 475 at
drivers/video/fbdev/core/fbmem.c:77 put_fb_info+0x18/0x68
[  657.135284] Modules linked in: radeonfb(+) uinput
snd_aoa_codec_toonie snd_aoa_fabric_layout snd_aoa snd_aoa_i2sbus
snd_aoa_soundbus snd_pcm snd_timer snd soundcore rack_meter evdev
i2c_dev sg usb_storage ip_tables x_tables autofs4 ext4 crc16 mbcache
jbd2 fscrypto hid_generic usbhid hid ohci_pci ehci_pci ohci_hcd
ehci_hcd sungem firewire_ohci sungem_phy sr_mod firewire_core
crc_itu_t cdrom sd_mod usbcore
[  657.135344] CPU: 0 PID: 475 Comm: modprobe Tainted: G        W
  4.15.0+ #321
[  657.135348] NIP:  c039e6ec LR: c039e834 CTR: 00000000
[  657.135352] REGS: dec93af0 TRAP: 0700   Tainted: G        W         (4.15.0+)
[  657.135355] MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 24228822  XER: 20000000
[  657.135365]
               GPR00: c039e834 dec93ba0 dc28eaa0 dc198800 00000000
000005c0 00000002 00000000
               GPR08: 00001032 c08c2c2c 00000000 c08c1ab0 28228424
0049ce6c e2287b5c 00000000
               GPR16: c06974dc 00000007 e2284384 00000001 dec9852c
e2282610 00000000 000a0000
               GPR24: c07c9d60 c07c9d2c dc19880c 00000000 dec93bb8
00000000 c0931a84 dc198800
[  657.135405] NIP [c039e6ec] put_fb_info+0x18/0x68
[  657.135411] LR [c039e834] do_unregister_framebuffer+0xf8/0x148
[  657.135413] Call Trace:
[  657.135419] [dec93bb0] [c039e834] do_unregister_framebuffer+0xf8/0x148
[  657.135425] [dec93be0] [c039ea1c]
do_remove_conflicting_framebuffers+0x198/0x1b8
[  657.135431] [dec93c30] [c039ea84] remove_conflicting_framebuffers+0x48/0x6c
[  657.135474] [dec93c50] [e2274d6c]
radeonfb_pci_register+0x184/0x1838 [radeonfb]
[  657.135481] [dec93cb0] [c037e9fc] pci_device_probe+0x110/0x180
[  657.135492] [dec93ce0] [c045be70] driver_probe_device+0x378/0x4a0
[  657.135497] [dec93d10] [c045c0ac] __driver_attach+0x114/0x118
[  657.135503] [dec93d30] [c04593dc] bus_for_each_dev+0x74/0xc0
[  657.135508] [dec93d60] [c045acd4] bus_add_driver+0x18c/0x2a0
[  657.135515] [dec93d80] [c045ce3c] driver_register+0x94/0x13c
[  657.135524] [dec93d90] [c0004af4] do_one_initcall+0x4c/0x178
[  657.135536] [dec93df0] [c00ced18] do_init_module+0x70/0x1ec
[  657.135542] [dec93e10] [c00cdcb0] load_module+0x20d8/0x26b8
[  657.135548] [dec93ec0] [c00ce500] SyS_finit_module+0xc4/0x120
[  657.135555] [dec93f40] [c00181cc] ret_from_syscall+0x0/0x40
[  657.135562] --- interrupt: c01 at 0x34d450
                   LR = 0x476108
[  657.135566] Instruction dump:
[  657.135572] 80010014 38210010 7c0803a6 4e800020 38600000 4e800020
7c0802a6 90010004
[  657.135582] 60000000 9421fff0 7c0802a6 90010014 <0fe00000> 7d401828
314affff 7d40192d
[  657.135593] ---[ end trace e0bf4192eb1c4f63 ]---
[  657.135613] device: 'vtcon1': device_unregister
[  657.135644] PM: Removing info for No Bus:vtcon1


Full dmesg:
https://people.debian.org/~malat/dmesg_radeonfb.txt

Does that help at all? the call stack does not make much sense to me.
I am accessing the Mac Mini over ssh.

Thank you, it helps.

User-space is holding reference on the /dev/fb0 and old fb_info
(from offb) while offb is being replaced by radeonfb (this is
why ->fb_destroy is never called). You may try checking with
lsof command to see what is holding /dev/fb0 open..

Right, I totally missed that X was running:

$ sudo lsof /dev/fb0
COMMAND PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
Xorg    469 root  mem    CHR   29,0          6500 /dev/fb0
Xorg    469 root   12u   CHR   29,0      0t0 6500 /dev/fb0

so I simply:

$ dmesg > before_xdm_stop
$ sudo service xdm stop
$ dmesg > after_xdm_stop
$ sudo lsof /dev/fb0
-> nothing

And I can verify in dmesg the call to put_fb_info:

$ diff -u before_xdm_stop after_xdm_stop

@@ -1589,3 +1589,31 @@
 [   19.650088] gem 0002:20:0f.0 eth0: Link is up at 100 Mbps, full-duplex
 [   19.650211] gem 0002:20:0f.0 eth0: Pause is disabled
 [   19.650245] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
+[   38.545478] WARNING: CPU: 0 PID: 468 at

drivers/video/fbdev/core/fbmem.c:77 put_fb_info+0x18/0x68
+[   38.545772] Modules linked in: uinput arc4 b43 bcma mac80211
snd_aoa_codec_toonie snd_aoa_fabric_layout snd_aoa sha256_generic
cfg80211 evdev sg snd_aoa_i2sbus snd_aoa_soundbus snd_pcm snd_timer
snd soundcore ssb usb_storage autofs4 ext4 crc16 mbcache jbd2 fscrypto
usbhid ohci_pci ehci_pci ohci_hcd ehci_hcd sungem firewire_ohci
sungem_phy firewire_core crc_itu_t sr_mod usbcore cdrom sd_mod
nls_base usb_common
+[   38.546894] CPU: 0 PID: 468 Comm: Xorg Tainted: G        W
4.15.0+ #31
+[   38.547103] NIP:  c03083ec LR: c0308bb0 CTR: c0308b48
+[   38.547252] REGS: de661dc0 TRAP: 0700   Tainted: G        W
 (4.15.0+)
+[   38.547459] MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 22002222  XER: 20000000
+[   38.547661]
+               GPR00: c0308bb0 de661e70 ddd108c0 dee02c00 de0febe0
de0febe8 00000001 ddd108c0
+               GPR08: 00000000 c07b0a40 00000000 df501e10 22002428
007e0ff4 00000000 00000000
+               GPR16: 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000
+               GPR24: ddd108c0 de0febe8 dede1c10 df30bbb0 df501e10
dede1c10 dee02c10 dee02c00
+[   38.548684] NIP [c03083ec] put_fb_info+0x18/0x68
+[   38.548821] LR [c0308bb0] fb_release+0x68/0x80
+[   38.548951] Call Trace:
+[   38.549026] [de661e70] [dede1c10] 0xdede1c10 (unreliable)
+[   38.549186] [de661e80] [c0308bb0] fb_release+0x68/0x80
+[   38.549344] [de661e90] [c01c1198] __fput+0xac/0x20c
+[   38.553889] [de661ec0] [c0062140] task_work_run+0xc0/0xe8
+[   38.558437] [de661ee0] [c0048918] do_exit+0x268/0x964
+[   38.562960] [de661f20] [c00490b4] do_group_exit+0x4c/0xb0
+[   38.567400] [de661f30] [c0049138] __wake_up_parent+0x0/0x3c
+[   38.571740] [de661f40] [c00151bc] ret_from_syscall+0x0/0x38
+[   38.575965] --- interrupt: c01 at 0xb794a778
+                   LR = 0xb794a748
+[   38.584039] Instruction dump:
+[   38.587878] 80010014 38210010 7c0803a6 4e800020 38600000 4e800020
7c0802a6 90010004
+[   38.595537] 60000000 9421fff0 7c0802a6 90010014 <0fe00000>
7d401828 314affff 7d40192d
+[   38.603316] ---[ end trace ee2e036160cab00c ]---


Now with your WARN_ON patch and xdm service stopped, here is what I get:

https://people.debian.org/~malat/full_xdm_stop_offb_without.log

You'll see that modprobe to radeonfb still fails.

If you now compare with the patch (v4) applied (+ WARN_ON and xdm
service stopped):

https://people.debian.org/~malat/full_xdm_stop_offb_with.log

You'll see a printk INFO for the call to offb_destroy:

...
[   48.025983]  MM calling offb_destroy
...

offb_destroy is called too late, which explains the failure for
loading radeonfb without the patch.

-M

quoted

For reference, the patch I used is:
https://github.com/malaterre/linux/commit/89fd7d4438c5200a1a4fcba1d60dd701fda4f40e.patch

quoted

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Signed-off-by: Mathieu Malaterre <redacted>
Link: https://bugs.debian.org/826629#57
Link: https://bugzilla.kernel.org/show_bug.cgi?id=119741
Suggested-by: Lennart Sorensen <redacted>
---
v2: Only fails when CONFIG_PCC is not set
v3: Only fails when CONFIG_FB_OF is not set, CONFIG_PCC was too broad. Since the conflicts in region is due to OFfb explicitly refers to it.

It seems that there may still be configurations when this is
incorrect -> when offb drives primary (non-radeon) card and radeonfb
drives secondary (radeon) card..

quoted

 drivers/video/fbdev/aty/radeon_base.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/video/fbdev/aty/radeon_base.c b/drivers/video/fbdev/aty/radeon_base.c
index 4d77daeecf99..221879196531 100644
--- a/drivers/video/fbdev/aty/radeon_base.c
+++ b/drivers/video/fbdev/aty/radeon_base.c

@@ -2259,6 +2259,22 @@ static const struct bin_attribute edid2_attr = {
      .read   = radeon_show_edid2,
 };

+static int radeon_kick_out_firmware_fb(struct pci_dev *pdev)
+{
+     struct apertures_struct *ap;
+
+     ap = alloc_apertures(1);
+     if (!ap)
+             return -ENOMEM;
+
+     ap->ranges[0].base = pci_resource_start(pdev, 0);
+     ap->ranges[0].size = pci_resource_len(pdev, 0);
+
+     remove_conflicting_framebuffers(ap, KBUILD_MODNAME, false);
+     kfree(ap);
+
+     return 0;
+}

 static int radeonfb_pci_register(struct pci_dev *pdev,
                               const struct pci_device_id *ent)

@@ -2312,19 +2328,27 @@ static int radeonfb_pci_register(struct pci_dev *pdev,
      rinfo->fb_base_phys = pci_resource_start (pdev, 0);
      rinfo->mmio_base_phys = pci_resource_start (pdev, 2);

+     ret = radeon_kick_out_firmware_fb(pdev);
+     if (ret)
+             return ret;
+
      /* request the mem regions */
      ret = pci_request_region(pdev, 0, "radeonfb framebuffer");
      if (ret < 0) {
+#ifndef CONFIG_FB_OF
              printk( KERN_ERR "radeonfb (%s): cannot request region 0.\n",
                      pci_name(rinfo->pdev));
              goto err_release_fb;
+#endif
      }

      ret = pci_request_region(pdev, 2, "radeonfb mmio");
      if (ret < 0) {
+#ifndef CONFIG_FB_OF
              printk( KERN_ERR "radeonfb (%s): cannot request region 2.\n",
                      pci_name(rinfo->pdev));
              goto err_release_pci0;
+#endif
      }

      /* map the regions */

@@ -2509,10 +2533,12 @@ static int radeonfb_pci_register(struct pci_dev *pdev,
      iounmap(rinfo->mmio_base);
 err_release_pci2:
      pci_release_region(pdev, 2);
+#ifndef CONFIG_FB_OF
 err_release_pci0:
      pci_release_region(pdev, 0);
 err_release_fb:
         framebuffer_release(info);
+#endif
 err_disable:
 err_out:
      return ret;

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics