linux.git/drivers/gpu/drm/panthor/Kconfig, branch master Linux kernel source tree drm/panthor: Part ways with drm_gem_shmem_object 2026-04-03T11:23:28+00:00 Boris Brezillon boris.brezillon@collabora.com 2026-04-01T13:48:50+00:00 68cbf96b1e9b96af3ad866b96b5c2092cb915c6c While drm_gem_shmem_object does most of the job we need it to do, the way sub-resources (pages, sgt, vmap) are handled and their lifetimes gets in the way of BO reclaim. There has been attempts to address that [1], but in the meantime, new gem_shmem users were introduced (accel drivers), and some of them manually free some of these resources. This makes things harder to control/sanitize/validate. Thomas Zimmerman is not a huge fan of enforcing lifetimes of sub-resources and forcing gem_shmem users to go through new gem_shmem helpers when they need manual control of some sort, and I believe this is a dead end if we don't force users to follow some stricter rules through carefully designed helpers, because there will always be one user doing crazy things with gem_shmem_object internals, which ends up tripping out the common helpers when they are called. The consensus we reached was that we would be better off forking gem_shmem in panthor. So here we are, parting ways with gem_shmem. The current transition tries to minimize the changes, but there are still some aspects that are different, the main one being that we no longer have a pages_use_count, and pages stays around until the GEM object is destroyed (or when evicted once we've added a shrinker). The sgt also no longer retains pages. This is losely based on how msm does things by the way. If there's any interest in sharing code (probably with msm, since the panthor shrinker is going to be losely based on the msm implementation), we can always change gears and do that once we have everything working/merged. [1]https://patchwork.kernel.org/project/dri-devel/patch/20240105184624.508603-1-dmitry.osipenko@collabora.com/ v2: - Fix refcounting - Add a _locked suffix to a bunch of functions expecting the resv lock to be held - Take the lock before releasing resources in panthor_gem_free_object() v3: - Use ERR_CAST() to fix an ERR-ptr deref - Add missing resv_[un]lock() around a panthor_gem_backing_unpin_locked() call v4: - Fix an error path in panthor_gem_vmap_get_locked() - Don't leave bo->base.pages with an ERR_PTR() - Make panthor_gem_{pin,unpin}[_locked]() more consistent - Don't fail in panthor_gem_dev_map_get_sgt_locked() if the pages are not allocated v5: - Add missing static specifier on our vm_ops v6: - Fix huge_fault handling - s/uint32_t/u32/ - s/drm_dbg_kms/drm_dbg_driver/ - Collect R-bs v7: - No changes Reviewed-by: Steven Price <steven.price@arm.com> Reviewed-by: Liviu Dudau <liviu.dudau@arm.com> Link: https://patch.msgid.link/20260401134854.2275433-7-boris.brezillon@collabora.com Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com> 
While drm_gem_shmem_object does most of the job we need it to do, the
way sub-resources (pages, sgt, vmap) are handled and their lifetimes
gets in the way of BO reclaim. There has been attempts to address
that [1], but in the meantime, new gem_shmem users were introduced
(accel drivers), and some of them manually free some of these resources.
This makes things harder to control/sanitize/validate.

Thomas Zimmerman is not a huge fan of enforcing lifetimes of sub-resources
and forcing gem_shmem users to go through new gem_shmem helpers when they
need manual control of some sort, and I believe this is a dead end if
we don't force users to follow some stricter rules through carefully
designed helpers, because there will always be one user doing crazy things
with gem_shmem_object internals, which ends up tripping out the common
helpers when they are called.

The consensus we reached was that we would be better off forking
gem_shmem in panthor. So here we are, parting ways with gem_shmem. The
current transition tries to minimize the changes, but there are still
some aspects that are different, the main one being that we no longer
have a pages_use_count, and pages stays around until the GEM object is
destroyed (or when evicted once we've added a shrinker). The sgt also
no longer retains pages. This is losely based on how msm does things by
the way.

If there's any interest in sharing code (probably with msm, since the
panthor shrinker is going to be losely based on the msm implementation),
we can always change gears and do that once we have everything
working/merged.

[1]https://patchwork.kernel.org/project/dri-devel/patch/20240105184624.508603-1-dmitry.osipenko@collabora.com/

v2:
- Fix refcounting
- Add a _locked suffix to a bunch of functions expecting the resv lock
  to be held
- Take the lock before releasing resources in panthor_gem_free_object()

v3:
- Use ERR_CAST() to fix an ERR-ptr deref
- Add missing resv_[un]lock() around a panthor_gem_backing_unpin_locked()
  call

v4:
- Fix an error path in panthor_gem_vmap_get_locked()
- Don't leave bo->base.pages with an ERR_PTR()
- Make panthor_gem_{pin,unpin}[_locked]() more consistent
- Don't fail in panthor_gem_dev_map_get_sgt_locked() if the pages are not
  allocated

v5:
- Add missing static specifier on our vm_ops

v6:
- Fix huge_fault handling
- s/uint32_t/u32/
- s/drm_dbg_kms/drm_dbg_driver/
- Collect R-bs

v7:
- No changes

Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patch.msgid.link/20260401134854.2275433-7-boris.brezillon@collabora.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Revert "drm/panthor: Fix undefined panthor_device_suspend/resume symbol issue" 2024-03-11T12:16:10+00:00 Jani Nikula jani.nikula@intel.com 2024-03-11T11:16:19+00:00 57a4e3a94caee6cfda41700da877bee77eab939c This reverts commit 674dc7f61aefea81901c21402946074927e63f1a. The commit causes a recursive dependency in kconfig: drivers/iommu/Kconfig:14:error: recursive dependency detected! drivers/iommu/Kconfig:14: symbol IOMMU_SUPPORT is selected by DRM_PANTHOR drivers/gpu/drm/panthor/Kconfig:3: symbol DRM_PANTHOR depends on PM kernel/power/Kconfig:183: symbol PM is selected by PM_SLEEP kernel/power/Kconfig:117: symbol PM_SLEEP depends on HIBERNATE_CALLBACKS kernel/power/Kconfig:35: symbol HIBERNATE_CALLBACKS is selected by XEN_SAVE_RESTORE arch/x86/xen/Kconfig:67: symbol XEN_SAVE_RESTORE depends on XEN arch/x86/xen/Kconfig:6: symbol XEN depends on PARAVIRT arch/x86/Kconfig:781: symbol PARAVIRT is selected by HYPERV drivers/hv/Kconfig:5: symbol HYPERV depends on X86_LOCAL_APIC arch/x86/Kconfig:1106: symbol X86_LOCAL_APIC depends on X86_UP_APIC arch/x86/Kconfig:1081: symbol X86_UP_APIC prompt is visible depending on PCI_MSI drivers/pci/Kconfig:39: symbol PCI_MSI is selected by AMD_IOMMU drivers/iommu/amd/Kconfig:3: symbol AMD_IOMMU depends on IOMMU_SUPPORT For a resolution refer to Documentation/kbuild/kconfig-language.rst subsection "Kconfig recursive dependency limitations" Fixes: 674dc7f61aef ("drm/panthor: Fix undefined panthor_device_suspend/resume symbol issue") Cc: Boris Brezillon <boris.brezillon@collabora.com> Cc: Liviu Dudau <liviu.dudau@arm.com> Cc: Steven Price <steven.price@arm.com> Acked-by: Boris Brezillon <boris.brezillon@collabora.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240311111619.249776-1-jani.nikula@intel.com Signed-off-by: Jani Nikula <jani.nikula@intel.com> 
This reverts commit 674dc7f61aefea81901c21402946074927e63f1a.

The commit causes a recursive dependency in kconfig:

drivers/iommu/Kconfig:14:error: recursive dependency detected!
drivers/iommu/Kconfig:14:	symbol IOMMU_SUPPORT is selected by DRM_PANTHOR
drivers/gpu/drm/panthor/Kconfig:3:	symbol DRM_PANTHOR depends on PM
kernel/power/Kconfig:183:	symbol PM is selected by PM_SLEEP
kernel/power/Kconfig:117:	symbol PM_SLEEP depends on HIBERNATE_CALLBACKS
kernel/power/Kconfig:35:	symbol HIBERNATE_CALLBACKS is selected by XEN_SAVE_RESTORE
arch/x86/xen/Kconfig:67:	symbol XEN_SAVE_RESTORE depends on XEN
arch/x86/xen/Kconfig:6:	symbol XEN depends on PARAVIRT
arch/x86/Kconfig:781:	symbol PARAVIRT is selected by HYPERV
drivers/hv/Kconfig:5:	symbol HYPERV depends on X86_LOCAL_APIC
arch/x86/Kconfig:1106:	symbol X86_LOCAL_APIC depends on X86_UP_APIC
arch/x86/Kconfig:1081:	symbol X86_UP_APIC prompt is visible depending on PCI_MSI
drivers/pci/Kconfig:39:	symbol PCI_MSI is selected by AMD_IOMMU
drivers/iommu/amd/Kconfig:3:	symbol AMD_IOMMU depends on IOMMU_SUPPORT
For a resolution refer to Documentation/kbuild/kconfig-language.rst
subsection "Kconfig recursive dependency limitations"

Fixes: 674dc7f61aef ("drm/panthor: Fix undefined panthor_device_suspend/resume symbol issue")
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Steven Price <steven.price@arm.com>
Acked-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240311111619.249776-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
drm/panthor: Fix undefined panthor_device_suspend/resume symbol issue 2024-03-11T09:50:37+00:00 Boris Brezillon boris.brezillon@collabora.com 2024-03-04T09:08:12+00:00 674dc7f61aefea81901c21402946074927e63f1a panthor_device_resume/suspend() are only compiled when CONFIG_PM is enabled but panthro_drv.c doesn't use the pm_ptr() macro to conditionally discard resume/suspend assignments, which causes undefined symbol errors at link time when !PM. We could fix that by using pm_ptr(), but supporting the !PM case makes little sense (the whole point of these embedded GPUs is to be low power, so proper PM is a basic requirement in that case). So let's just enforce the presence of CONFIG_PM with a Kconfig dependency instead. If someone needs to relax this dependency, it can be done in a follow-up. Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202403031944.EOimQ8WK-lkp@intel.com/ Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com> Reviewed-by: Liviu Dudau <liviu.dudau@arm.com> Reviewed-by: Steven Price <steven.price@arm.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240304090812.3941084-4-boris.brezillon@collabora.com 
panthor_device_resume/suspend() are only compiled when CONFIG_PM is
enabled but panthro_drv.c doesn't use the pm_ptr() macro to conditionally
discard resume/suspend assignments, which causes undefined symbol
errors at link time when !PM.

We could fix that by using pm_ptr(), but supporting the !PM case makes
little sense (the whole point of these embedded GPUs is to be low power,
so proper PM is a basic requirement in that case). So let's just enforce
the presence of CONFIG_PM with a Kconfig dependency instead.

If someone needs to relax this dependency, it can be done in a follow-up.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202403031944.EOimQ8WK-lkp@intel.com/
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240304090812.3941084-4-boris.brezillon@collabora.com
drm/panthor: Allow driver compilation 2024-03-01T09:04:29+00:00 Boris Brezillon boris.brezillon@collabora.com 2024-02-29T16:22:26+00:00 d72f049087d4f973f6332b599c92177e718107de Now that all blocks are available, we can add/update Kconfig/Makefile files to allow compilation. v6: - Add Maxime's and Heiko's acks - Keep source files alphabetically ordered in the Makefile v4: - Add Steve's R-b v3: - Add a dep on DRM_GPUVM - Fix dependencies in Kconfig - Expand help text to (hopefully) describe which GPUs are to be supported by this driver and which are for panfrost. Co-developed-by: Steven Price <steven.price@arm.com> Signed-off-by: Steven Price <steven.price@arm.com> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com> Acked-by: Steven Price <steven.price@arm.com> # MIT+GPL2 relicensing,Arm Acked-by: Grant Likely <grant.likely@linaro.org> # MIT+GPL2 relicensing,Linaro Acked-by: Boris Brezillon <boris.brezillon@collabora.com> # MIT+GPL2 relicensing,Collabora Reviewed-by: Steven Price <steven.price@arm.com> Acked-by: Maxime Ripard <mripard@kernel.org> Acked-by: Heiko Stuebner <heiko@sntech.de> Link: https://patchwork.freedesktop.org/patch/msgid/20240229162230.2634044-13-boris.brezillon@collabora.com 
Now that all blocks are available, we can add/update Kconfig/Makefile
files to allow compilation.

v6:
- Add Maxime's and Heiko's acks
- Keep source files alphabetically ordered in the Makefile

v4:
- Add Steve's R-b

v3:
- Add a dep on DRM_GPUVM
- Fix dependencies in Kconfig
- Expand help text to (hopefully) describe which GPUs are to be
  supported by this driver and which are for panfrost.

Co-developed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Steven Price <steven.price@arm.com> # MIT+GPL2 relicensing,Arm
Acked-by: Grant Likely <grant.likely@linaro.org> # MIT+GPL2 relicensing,Linaro
Acked-by: Boris Brezillon <boris.brezillon@collabora.com> # MIT+GPL2 relicensing,Collabora
Reviewed-by: Steven Price <steven.price@arm.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240229162230.2634044-13-boris.brezillon@collabora.com