gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

11 messages, 4 authors, 2021-10-27 · open the first message on its own page

gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Naresh Kamboju <hidden>
Date: 2021-10-25 12:14:09

Regression found on arm gcc-11 built with multi_v5_defconfig
Following build warnings / errors reported on linux next 20211025.

metadata:
    git_describe: next-20211025
    git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
    git_short_log: 9ae1fbdeabd3 (\"Add linux-next specific files for 20211025\")
    target_arch: arm
    toolchain: gcc-11
    config: multi_v5_defconfig

build error :
--------------
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_get_gem_obj':
drivers/gpu/drm/drm_fb_cma_helper.c:46: undefined reference to
`drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_sync_non_coherent':
drivers/gpu/drm/drm_fb_cma_helper.c:133: undefined reference to
`drm_atomic_helper_damage_iter_init'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:135:
undefined reference to `drm_atomic_helper_damage_iter_next'
make[1]: *** [Makefile:1252: vmlinux] Error 1
make[1]: Target '__all' not remade because of errors.
make: *** [Makefile:226: __sub-make] Error 2

Reported-by: Linux Kernel Functional Testing <redacted>


build link:
-----------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/build.log

build config:
-------------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/config

# To install tuxmake on your system globally
# sudo pip3 install -U tuxmake
tuxmake --runtime podman --target-arch arm --toolchain gcc-11
--kconfig multi_v5_defconfig

--
Linaro LKFT
https://lkft.linaro.org

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Naresh Kamboju <hidden>
Date: 2021-10-25 14:04:26

On Mon, 25 Oct 2021 at 17:43, Naresh Kamboju [off-list ref] wrote:
Regression found on arm gcc-11 built with multi_v5_defconfig
Following build warnings / errors reported on linux next 20211025.

metadata:
    git_describe: next-20211025
    git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
    git_short_log: 9ae1fbdeabd3 (\"Add linux-next specific files for 20211025\")
    target_arch: arm
    toolchain: gcc-11
    config: multi_v5_defconfig

build error :
--------------
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_get_gem_obj':
drivers/gpu/drm/drm_fb_cma_helper.c:46: undefined reference to
`drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_sync_non_coherent':
drivers/gpu/drm/drm_fb_cma_helper.c:133: undefined reference to
`drm_atomic_helper_damage_iter_init'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:135:
undefined reference to `drm_atomic_helper_damage_iter_next'
make[1]: *** [Makefile:1252: vmlinux] Error 1
make[1]: Target '__all' not remade because of errors.
make: *** [Makefile:226: __sub-make] Error 2

Reported-by: Linux Kernel Functional Testing <redacted>
The bisection script pointed to the first bad commit,

commit 4b2b5e142ff499a2bef2b8db0272bbda1088a3fe
drm: Move GEM memory managers into modules
build link:
-----------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/build.log

build config:
-------------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/config

# To install tuxmake on your system globally
# sudo pip3 install -U tuxmake
tuxmake --runtime podman --target-arch arm --toolchain gcc-11
--kconfig multi_v5_defconfig

--
Linaro LKFT
https://lkft.linaro.org
- Naresh

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Thomas Zimmermann <tzimmermann@suse.de>
Date: 2021-10-26 17:59:44

Hi

Am 25.10.21 um 16:01 schrieb Naresh Kamboju:
On Mon, 25 Oct 2021 at 17:43, Naresh Kamboju [off-list ref] wrote:
quoted
Regression found on arm gcc-11 built with multi_v5_defconfig
Following build warnings / errors reported on linux next 20211025.

metadata:
     git_describe: next-20211025
     git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
     git_short_log: 9ae1fbdeabd3 (\"Add linux-next specific files for 20211025\")
     target_arch: arm
     toolchain: gcc-11
     config: multi_v5_defconfig

build error :
--------------
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_get_gem_obj':
drivers/gpu/drm/drm_fb_cma_helper.c:46: undefined reference to
`drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_sync_non_coherent':
drivers/gpu/drm/drm_fb_cma_helper.c:133: undefined reference to
`drm_atomic_helper_damage_iter_init'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:135:
undefined reference to `drm_atomic_helper_damage_iter_next'
make[1]: *** [Makefile:1252: vmlinux] Error 1
make[1]: Target '__all' not remade because of errors.
make: *** [Makefile:226: __sub-make] Error 2

Reported-by: Linux Kernel Functional Testing <redacted>
The bisection script pointed to the first bad commit,

commit 4b2b5e142ff499a2bef2b8db0272bbda1088a3fe
drm: Move GEM memory managers into modules
Could you please try the patch at [1]? It fixes the problem for me.

Best regards
Thomas

[1] https://patchwork.freedesktop.org/patch/461426/
quoted
build link:
-----------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/build.log

build config:
-------------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/config

# To install tuxmake on your system globally
# sudo pip3 install -U tuxmake
tuxmake --runtime podman --target-arch arm --toolchain gcc-11
--kconfig multi_v5_defconfig

--
Linaro LKFT
https://lkft.linaro.org
- Naresh
-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Naresh Kamboju <hidden>
Date: 2021-10-27 02:57:05

Hi Thomas,

I have tested the fix patch [1] and it works fine for me.
Could you please try the patch at [1]? It fixes the problem for me.
🎉 Pass: 6d61a7c3bc2a ("arm: multi_v5_defconfig build fix")
 arm (multi_v5_defconfig) with gcc-11
@ https://builds.tuxbuild.com/204SnLe1DFWQ4iAHpwAMiyUcpsL/

Best regards
Thomas

[1] https://patchwork.freedesktop.org/patch/461426/

Tested-by: Naresh Kamboju <redacted>

- Naresh

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Thomas Zimmermann <tzimmermann@suse.de>
Date: 2021-10-25 18:25:15

Hi

Am 25.10.21 um 14:13 schrieb Naresh Kamboju:
Regression found on arm gcc-11 built with multi_v5_defconfig
Following build warnings / errors reported on linux next 20211025.

metadata:
     git_describe: next-20211025
     git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
     git_short_log: 9ae1fbdeabd3 (\"Add linux-next specific files for 20211025\")
     target_arch: arm
     toolchain: gcc-11
     config: multi_v5_defconfig

build error :
--------------
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_get_gem_obj':
drivers/gpu/drm/drm_fb_cma_helper.c:46: undefined reference to
`drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_sync_non_coherent':
drivers/gpu/drm/drm_fb_cma_helper.c:133: undefined reference to
`drm_atomic_helper_damage_iter_init'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:135:
undefined reference to `drm_atomic_helper_damage_iter_next'
make[1]: *** [Makefile:1252: vmlinux] Error 1
make[1]: Target '__all' not remade because of errors.
make: *** [Makefile:226: __sub-make] Error 2

Reported-by: Linux Kernel Functional Testing <redacted>
That's probably from moving some of the functions into separate modules. 
Will be fixed soon.

Best regards
Thomas

build link:
-----------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/build.log

build config:
-------------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/config

# To install tuxmake on your system globally
# sudo pip3 install -U tuxmake
tuxmake --runtime podman --target-arch arm --toolchain gcc-11
--kconfig multi_v5_defconfig

--
Linaro LKFT
https://lkft.linaro.org
-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Thomas Zimmermann <tzimmermann@suse.de>
Date: 2021-10-26 18:21:53

Hi

Am 25.10.21 um 14:13 schrieb Naresh Kamboju:
Regression found on arm gcc-11 built with multi_v5_defconfig
Following build warnings / errors reported on linux next 20211025.

metadata:
     git_describe: next-20211025
     git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
     git_short_log: 9ae1fbdeabd3 (\"Add linux-next specific files for 20211025\")
     target_arch: arm
     toolchain: gcc-11
     config: multi_v5_defconfig

build error :
--------------
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_get_gem_obj':
drivers/gpu/drm/drm_fb_cma_helper.c:46: undefined reference to
`drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_sync_non_coherent':
drivers/gpu/drm/drm_fb_cma_helper.c:133: undefined reference to
`drm_atomic_helper_damage_iter_init'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:135:
undefined reference to `drm_atomic_helper_damage_iter_next'
make[1]: *** [Makefile:1252: vmlinux] Error 1
make[1]: Target '__all' not remade because of errors.
make: *** [Makefile:226: __sub-make] Error 2

Reported-by: Linux Kernel Functional Testing <redacted>


build link:
-----------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/build.log

build config:
-------------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/config
Looking at this config, there is:

CONFIG_DRM=y
# CONFIG_DRM_DP_AUX_CHARDEV is not set
# CONFIG_DRM_DEBUG_MM is not set
# CONFIG_DRM_DEBUG_SELFTEST is not set
CONFIG_DRM_KMS_HELPER=m
# CONFIG_DRM_LOAD_EDID_FIRMWARE is not set
# CONFIG_DRM_DP_CEC is not set
CONFIG_DRM_GEM_CMA_HELPER=y
CONFIG_DRM_KMS_CMA_HELPER=y

GEM_CMA_HELPER depends on KMS_HELPER, but the latter is a module. That's 
probably the cause of the problem. Is it intentionally set this way?

Best regards
Thomas
# To install tuxmake on your system globally
# sudo pip3 install -U tuxmake
tuxmake --runtime podman --target-arch arm --toolchain gcc-11
--kconfig multi_v5_defconfig

--
Linaro LKFT
https://lkft.linaro.org
-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Randy Dunlap <hidden>
Date: 2021-10-27 00:58:56

On 10/26/21 11:21 AM, Thomas Zimmermann wrote:
Hi

Am 25.10.21 um 14:13 schrieb Naresh Kamboju:
quoted
Regression found on arm gcc-11 built with multi_v5_defconfig
Following build warnings / errors reported on linux next 20211025.

metadata:
     git_describe: next-20211025
     git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
     git_short_log: 9ae1fbdeabd3 (\"Add linux-next specific files for 20211025\")
     target_arch: arm
     toolchain: gcc-11
     config: multi_v5_defconfig

build error :
--------------
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_get_gem_obj':
drivers/gpu/drm/drm_fb_cma_helper.c:46: undefined reference to
`drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:46:
undefined reference to `drm_gem_fb_get_obj'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.o: in
function `drm_fb_cma_sync_non_coherent':
drivers/gpu/drm/drm_fb_cma_helper.c:133: undefined reference to
`drm_atomic_helper_damage_iter_init'
arm-linux-gnueabihf-ld: drivers/gpu/drm/drm_fb_cma_helper.c:135:
undefined reference to `drm_atomic_helper_damage_iter_next'
make[1]: *** [Makefile:1252: vmlinux] Error 1
make[1]: Target '__all' not remade because of errors.
make: *** [Makefile:226: __sub-make] Error 2

Reported-by: Linux Kernel Functional Testing <redacted>


build link:
-----------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/build.log

build config:
-------------
https://builds.tuxbuild.com/1zzgFZBGjpQ5R0lawQFW9iJ39Hp/config
Looking at this config, there is:

CONFIG_DRM=y
# CONFIG_DRM_DP_AUX_CHARDEV is not set
# CONFIG_DRM_DEBUG_MM is not set
# CONFIG_DRM_DEBUG_SELFTEST is not set
CONFIG_DRM_KMS_HELPER=m
# CONFIG_DRM_LOAD_EDID_FIRMWARE is not set
# CONFIG_DRM_DP_CEC is not set
CONFIG_DRM_GEM_CMA_HELPER=y
CONFIG_DRM_KMS_CMA_HELPER=y

GEM_CMA_HELPER depends on KMS_HELPER, but the latter is a module. That's probably the cause of the problem. Is it intentionally set this way?
The only drivers that select DRM_KMS_HELPER are both =m, so that's how
DRM_KMS_HELPER is set also.

Symbol: DRM_KMS_HELPER [=m]
Type : tristate
Defined at drivers/gpu/drm/Kconfig:82
Depends on: HAS_IOMEM [=y] && DRM [=y]
Selected by [m]:
- DRM_ATMEL_HLCDC [=m] && HAS_IOMEM [=y] && DRM [=y] && OF [=y] && COMMON_CLK [=y] && MFD_ATMEL_HLCDC [=y] && ARM [=y]
- DRM_ASPEED_GFX [=m] && HAS_IOMEM [=y] && DRM [=y] && OF [=y] && (COMPILE_TEST [=n] || ARCH_ASPEED [=y]) && MMU [=y]


I did the ARM cross-build and also see the linker error.
I didn't understand why -- and still don't, but here is a little
speculation:

In the past (e.g. 10 years ago), we have to move some .o files
in lib/ from lib-y to obj-y so that they would always be included
in the final object file and not cause their user/caller object
files to suffer from undefined references.
These happened because unused functions(?) in lib-y files are
stripped out of the final object files.
The same thing could be happening here (still just guessing).

Does that help any?  I dunno.

Adding Arnd to Cc: to see if he has any ideas...
quoted
# To install tuxmake on your system globally
# sudo pip3 install -U tuxmake
tuxmake --runtime podman --target-arch arm --toolchain gcc-11
--kconfig multi_v5_defconfig

-- 
Linaro LKFT
https://lkft.linaro.org


-- 
~Randy

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Arnd Bergmann <arnd@arndb.de>
Date: 2021-10-27 06:20:10

On Wed, Oct 27, 2021 at 2:58 AM Randy Dunlap [off-list ref] wrote:
quoted
Looking at this config, there is:

CONFIG_DRM=y
# CONFIG_DRM_DP_AUX_CHARDEV is not set
# CONFIG_DRM_DEBUG_MM is not set
# CONFIG_DRM_DEBUG_SELFTEST is not set
CONFIG_DRM_KMS_HELPER=m
# CONFIG_DRM_LOAD_EDID_FIRMWARE is not set
# CONFIG_DRM_DP_CEC is not set
CONFIG_DRM_GEM_CMA_HELPER=y
CONFIG_DRM_KMS_CMA_HELPER=y

GEM_CMA_HELPER depends on KMS_HELPER, but the latter is a module. That's probably the cause of the problem. Is it intentionally set this way?
The only drivers that select DRM_KMS_HELPER are both =m, so that's how
DRM_KMS_HELPER is set also.

Symbol: DRM_KMS_HELPER [=m]
Type : tristate
Defined at drivers/gpu/drm/Kconfig:82
Depends on: HAS_IOMEM [=y] && DRM [=y]
Selected by [m]:
- DRM_ATMEL_HLCDC [=m] && HAS_IOMEM [=y] && DRM [=y] && OF [=y] && COMMON_CLK [=y] && MFD_ATMEL_HLCDC [=y] && ARM [=y]
- DRM_ASPEED_GFX [=m] && HAS_IOMEM [=y] && DRM [=y] && OF [=y] && (COMPILE_TEST [=n] || ARCH_ASPEED [=y]) && MMU [=y]


I did the ARM cross-build and also see the linker error.
I didn't understand why -- and still don't, but here is a little
speculation:

In the past (e.g. 10 years ago), we have to move some .o files
in lib/ from lib-y to obj-y so that they would always be included
in the final object file and not cause their user/caller object
files to suffer from undefined references.
These happened because unused functions(?) in lib-y files are
stripped out of the final object files.
The same thing could be happening here (still just guessing).

Does that help any?  I dunno.

Adding Arnd to Cc: to see if he has any ideas...
From all I can tell, the problem is that DRM_KMS_CMA_HELPER is a 'bool'
symbol, so if it gets selected by a '=m' driver, it turns into '=y', which
then selects DRM_GEM_CMA_HELPER=y, but that one cannot link
against DRM_KMS_HELPER=m code.

This trivial change makes it all build:
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index c08860db2520..699f434ce813 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -218,7 +218,7 @@ config DRM_GEM_CMA_HELPER
          Choose this if you need the GEM CMA helper functions

 config DRM_KMS_CMA_HELPER
-       bool
+       tristate
        depends on DRM
        select DRM_GEM_CMA_HELPER
        help
but this needs some more testing to make sure it doesn't add
any other regressions.

Interestingly, I never hit the problem in randconfig testing since
there is always some '=y' driver that selects DRM_KMS_HELPER.

        Arnd

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Randy Dunlap <hidden>
Date: 2021-10-27 06:26:20

On 10/26/21 11:19 PM, Arnd Bergmann wrote:
quoted hunk
On Wed, Oct 27, 2021 at 2:58 AM Randy Dunlap [off-list ref] wrote:
quoted
quoted
Looking at this config, there is:

CONFIG_DRM=y
# CONFIG_DRM_DP_AUX_CHARDEV is not set
# CONFIG_DRM_DEBUG_MM is not set
# CONFIG_DRM_DEBUG_SELFTEST is not set
CONFIG_DRM_KMS_HELPER=m
# CONFIG_DRM_LOAD_EDID_FIRMWARE is not set
# CONFIG_DRM_DP_CEC is not set
CONFIG_DRM_GEM_CMA_HELPER=y
CONFIG_DRM_KMS_CMA_HELPER=y

GEM_CMA_HELPER depends on KMS_HELPER, but the latter is a module. That's probably the cause of the problem. Is it intentionally set this way?
The only drivers that select DRM_KMS_HELPER are both =m, so that's how
DRM_KMS_HELPER is set also.

Symbol: DRM_KMS_HELPER [=m]
Type : tristate
Defined at drivers/gpu/drm/Kconfig:82
Depends on: HAS_IOMEM [=y] && DRM [=y]
Selected by [m]:
- DRM_ATMEL_HLCDC [=m] && HAS_IOMEM [=y] && DRM [=y] && OF [=y] && COMMON_CLK [=y] && MFD_ATMEL_HLCDC [=y] && ARM [=y]
- DRM_ASPEED_GFX [=m] && HAS_IOMEM [=y] && DRM [=y] && OF [=y] && (COMPILE_TEST [=n] || ARCH_ASPEED [=y]) && MMU [=y]


I did the ARM cross-build and also see the linker error.
I didn't understand why -- and still don't, but here is a little
speculation:

In the past (e.g. 10 years ago), we have to move some .o files
in lib/ from lib-y to obj-y so that they would always be included
in the final object file and not cause their user/caller object
files to suffer from undefined references.
These happened because unused functions(?) in lib-y files are
stripped out of the final object files.
The same thing could be happening here (still just guessing).

Does that help any?  I dunno.

Adding Arnd to Cc: to see if he has any ideas...
 From all I can tell, the problem is that DRM_KMS_CMA_HELPER is a 'bool'
symbol, so if it gets selected by a '=m' driver, it turns into '=y', which
then selects DRM_GEM_CMA_HELPER=y, but that one cannot link
against DRM_KMS_HELPER=m code.

This trivial change makes it all build:
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index c08860db2520..699f434ce813 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -218,7 +218,7 @@ config DRM_GEM_CMA_HELPER
           Choose this if you need the GEM CMA helper functions

  config DRM_KMS_CMA_HELPER
-       bool
+       tristate
         depends on DRM
         select DRM_GEM_CMA_HELPER
         help
but this needs some more testing to make sure it doesn't add
any other regressions.

Interestingly, I never hit the problem in randconfig testing since
there is always some '=y' driver that selects DRM_KMS_HELPER.

         Arnd
Hi Arnd,
Thomas had posted a patch that also fixes the problem.
Somehow I missed seeing that the first time around.

Thanks.
-- 
~Randy

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Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Arnd Bergmann <arnd@arndb.de>
Date: 2021-10-27 06:51:17

On Wed, Oct 27, 2021 at 8:26 AM Randy Dunlap [off-list ref] wrote:
On 10/26/21 11:19 PM, Arnd Bergmann wrote:
quoted
On Wed, Oct 27, 2021 at 2:58 AM Randy Dunlap [off-list ref] wrote:
quoted
This trivial change makes it all build:
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index c08860db2520..699f434ce813 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -218,7 +218,7 @@ config DRM_GEM_CMA_HELPER
           Choose this if you need the GEM CMA helper functions

  config
quoted
-       bool
+       tristate
         depends on DRM
         select DRM_GEM_CMA_HELPER
         help

but this needs some more testing to make sure it doesn't add
any other regressions.

Interestingly, I never hit the problem in randconfig testing since
there is always some '=y' driver that selects DRM_KMS_HELPER.
Thomas had posted a patch that also fixes the problem.
Somehow I missed seeing that the first time around.
Ah right, I missed that as well. That patch seems reasonable
to me, but I think we may want both of them in this case, as
it does not address DRM_GEM_CMA_HELPER being set to =y
when it is only used from modules.

       Arnd

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Re: gpu: drm_fb_cma_helper.c:46: undefined reference to `drm_gem_fb_get_obj'

From: Thomas Zimmermann <tzimmermann@suse.de>
Date: 2021-10-27 08:08:09

Hi!

Am 27.10.21 um 08:50 schrieb Arnd Bergmann:
On Wed, Oct 27, 2021 at 8:26 AM Randy Dunlap [off-list ref] wrote:
quoted
On 10/26/21 11:19 PM, Arnd Bergmann wrote:
quoted
On Wed, Oct 27, 2021 at 2:58 AM Randy Dunlap [off-list ref] wrote:
quoted
quoted
This trivial change makes it all build:
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index c08860db2520..699f434ce813 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -218,7 +218,7 @@ config DRM_GEM_CMA_HELPER
            Choose this if you need the GEM CMA helper functions

   config
quoted
quoted
-       bool
+       tristate
          depends on DRM
          select DRM_GEM_CMA_HELPER
          help

but this needs some more testing to make sure it doesn't add
any other regressions.

Interestingly, I never hit the problem in randconfig testing since
there is always some '=y' driver that selects DRM_KMS_HELPER.
Thomas had posted a patch that also fixes the problem.
Somehow I missed seeing that the first time around.
Ah right, I missed that as well. That patch seems reasonable
to me, but I think we may want both of them in this case, as
it does not address DRM_GEM_CMA_HELPER being set to =y
when it is only used from modules.
Yes, the bool state was indeed the problem. The patch I posted resolves 
the issue for now. For later, I have a patchset that improves CMA helper 
usage a bit and resolves the Kconfig problem.

Best regards
Thomas
        Arnd
-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
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