Jani Nikula [Fri, 1 Oct 2021 09:14:44 +0000 (12:14 +0300)]
drm/locking: add backtrace for locking contended locks without backoff
If drm_modeset_lock() returns -EDEADLK, the caller is supposed to drop
all currently held locks using drm_modeset_backoff(). Failing to do so
will result in warnings and backtraces on the paths trying to lock a
contended lock. Add support for optionally printing the backtrace on the
path that hit the deadlock and didn't gracefully handle the situation.
For example, the patch [1] inadvertently dropped the return value check
and error return on replacing calc_watermark_data() with
intel_compute_global_watermarks(). The backtraces on the subsequent
locking paths hitting WARN_ON(ctx->contended) were unhelpful, but adding
the backtrace to the deadlock path produced this helpful printout:
<7> [98.002465] drm_modeset_lock attempting to lock a contended lock without backoff:
drm_modeset_lock+0x107/0x130
drm_atomic_get_plane_state+0x76/0x150
skl_compute_wm+0x251d/0x2b20 [i915]
intel_atomic_check+0x1942/0x29e0 [i915]
drm_atomic_check_only+0x554/0x910
drm_atomic_nonblocking_commit+0xe/0x50
drm_mode_atomic_ioctl+0x8c2/0xab0
drm_ioctl_kernel+0xac/0x140
Add new CONFIG_DRM_DEBUG_MODESET_LOCK to enable modeset lock debugging
with stack depot and trace.
Karol Herbst [Tue, 12 Oct 2021 13:33:34 +0000 (15:33 +0200)]
drm/nouveau/mmu/gp100: remove unused variable
Fixes a compilation issue introduced because I forgot to test with WERROR
enabled.
Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: DRI <dri-devel@lists.freedesktop.org> Cc: nouveau@lists.freedesktop.org Fixes: af7fdb6a7619 ("drm/nouveau/mmu/gp100-: drop unneeded assignment in the if condition.") Acked-by: Adam Jackson <ajax@redhat.com> Reviewed-by: Lyude Paul <lyude@redhat.com> Signed-off-by: Karol Herbst <kherbst@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20211012133334.1737918-1-kherbst@redhat.com
Guido Günther [Mon, 11 Oct 2021 13:41:27 +0000 (15:41 +0200)]
drm: mxsfb: Set fallback bus format when the bridge doesn't provide one
If a bridge doesn't do any bus format handling MEDIA_BUS_FMT_FIXED is
returned. Fallback to a reasonable default (MEDIA_BUS_FMT_RGB888_1X24) in
that case.
This unbreaks e.g. using mxsfb with the nwl bridge and mipi dsi panels.
Components further up in the chain might ask us for supported formats.
Without this MEDIA_BUS_FMT_FIXED is assumed which then breaks display
output with mxsfb since it can't determine a proper bus format.
We handle the bus formats that correspond to the DSI formats the bridge
can potentially output (see chapter 13.6 of the i.MX 8MQ reference
manual) - which matches what xsfb can input.
Randy Dunlap [Sun, 10 Oct 2021 22:44:59 +0000 (15:44 -0700)]
drm/connector: fix all kernel-doc warnings
Clean up all of the kernel-doc issues in drm_connector.c:
drivers/gpu/drm/drm_connector.c:2611: warning: Excess function parameter 'connector' description in 'drm_connector_oob_hotplug_event'
drivers/gpu/drm/drm_connector.c:2611: warning: Function parameter or member 'connector_fwnode' not described in 'drm_connector_oob_hotplug_event'
drm_connector.c:630: warning: No description found for return value of 'drm_get_connector_status_name'
drm_connector.c:715: warning: No description found for return value of 'drm_connector_list_iter_next'
drm_connector.c:785: warning: No description found for return value of 'drm_get_subpixel_order_name'
drm_connector.c:816: warning: No description found for return value of 'drm_display_info_set_bus_formats'
drm_connector.c:1331: warning: No description found for return value of 'drm_mode_create_dvi_i_properties'
drm_connector.c:1412: warning: No description found for return value of 'drm_connector_attach_content_type_property'
drm_connector.c:1492: warning: No description found for return value of 'drm_mode_create_tv_margin_properties'
drm_connector.c:1534: warning: No description found for return value of 'drm_mode_create_tv_properties'
drm_connector.c:1627: warning: No description found for return value of 'drm_mode_create_scaling_mode_property'
drm_connector.c:1944: warning: No description found for return value of 'drm_mode_create_suggested_offset_properties'
drm_connector.c:2315: warning: missing initial short description on line:
* drm_connector_set_panel_orientation_with_quirk -
[The last warning listed is probably a quirk/bug in scripts/kernel-doc.]
Fixes: 900230512ce0 ("drm: locking&new iterators for connector_list") Fixes: 07d958be443e ("drm: Extract drm_connector.[hc]") Fixes: 1af28b53b613 ("drm: document drm_display_info") Fixes: 5f802dda2ff7 ("drm: content-type property for HDMI connector") Fixes: d1fc07278cc6 ("drm/connector: Allow creation of margin props alone") Fixes: fc3a776280b0 ("drm/connector: Split out orientation quirk detection (v2)") Fixes: 85b856bdf17f ("drm/connector: Add support for out-of-band hotplug notification (v3)") Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: David Airlie <airlied@linux.ie> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: dri-devel@lists.freedesktop.org Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Cc: Derek Basehore <dbasehore@chromium.org> Cc: Hans de Goede <hdegoede@redhat.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: Sam Ravnborg <sam@ravnborg.org> Signed-off-by: Sam Ravnborg <sam@ravnborg.org> Link: https://patchwork.freedesktop.org/patch/msgid/20211010224459.3603-1-rdunlap@infradead.org
Uwe Kleine-König [Mon, 11 Oct 2021 13:27:42 +0000 (15:27 +0200)]
drm/panel: s6e63m0: Make s6e63m0_remove() return void
Up to now s6e63m0_remove() returns zero unconditionally. Make it return
void instead which makes it easier to see in the callers that there is
no error to handle.
Also the return value of spi remove callbacks is ignored anyway.
Tvrtko Ursulin [Fri, 8 Oct 2021 09:50:07 +0000 (10:50 +0100)]
dma-resv: Fix dma_resv_get_fences and dma_resv_copy_fences after conversion
Cache the count of shared fences in the iterator to avoid dereferencing
the dma_resv_object outside the RCU protection. Otherwise iterator and its
users can observe an incosistent state which makes it impossible to use
safely. Such as:
If the shared object has changed during the RCU unlocked period
callers will correctly handle the restart on the next iteration.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Fixes: 057006da7de7 ("dma-buf: use new iterator in dma_resv_copy_fences") Fixes: e2a66cc22c6d ("dma-buf: use new iterator in dma_resv_get_fences v3") Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4274 Cc: Christian König <christian.koenig@amd.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org Link: https://patchwork.freedesktop.org/patch/msgid/20211008095007.972693-1-tvrtko.ursulin@linux.intel.com Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Christian König <christian.koenig@amd.com>
drivers/gpu/drm/nouveau/nouveau_bo.c: In function ‘nouveau_ttm_tt_populate’:
drivers/gpu/drm/nouveau/nouveau_bo.c:1228:17: warning: variable ‘dev’ set but not used [-Wunused-but-set-variable]
drivers/gpu/drm/nouveau/nouveau_bo.c: In function ‘nouveau_ttm_tt_unpopulate’:
drivers/gpu/drm/nouveau/nouveau_bo.c:1252:17: warning: variable ‘dev’ set but not used [-Wunused-but-set-variable]
Cc: Ben Skeggs <bskeggs@redhat.com> Cc: David Airlie <airlied@linux.ie> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: "Christian König" <christian.koenig@amd.com> Cc: Jeremy Kolb <jkolb@brandeis.edu> Cc: dri-devel@lists.freedesktop.org Cc: nouveau@lists.freedesktop.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Signed-off-by: Lee Jones <lee.jones@linaro.org> Reviewed-by: Karol Herbst <kherbst@redhat.com> Signed-off-by: Karol Herbst <kherbst@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20210416143725.2769053-8-lee.jones@linaro.org
Luo penghao [Sat, 21 Aug 2021 02:14:47 +0000 (19:14 -0700)]
drm/nouveau/mmu/gp100-: drop unneeded assignment in the if condition.
In order to keep the code style consistency of the whole file,
the 'inst' assignments should be deleted.
The clang_analyzer complains as follows:
drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmmgp100.c:499:8: warning:
Although the value storedto 'inst' is used in the enclosing expression,
the value is never actually read from 'inst'.
Luo penghao [Sat, 21 Aug 2021 02:11:06 +0000 (19:11 -0700)]
drm/nouveau/mmu: drop unneeded assignment in the nvkm_uvmm_mthd_page()
In order to keep the code style consistency of the whole file,
the 'ret' assignments should be deleted.
The clang_analyzer complains as follows:
drivers/gpu/drm/nouveau/nvkm/subdev/mmu/uvmm.c:317:8:warning:
Although the value storedto 'ret' is used in the enclosing expression,
the value is never actually read from 'ret'.
drm/panel: Add support for Sharp LS060T1SX01 panel
Add driver to support Sharp LS06T1SX01 FullHD panel. The panel uses
nt35695 driver IC. For example this LCD module can be found in the
kwaek.ca Dragonboard Display Adapter Bundle.
dt-bindings: add bindings for the Sharp LS060T1SX01 panel
Add devicetree bindings for the Sharp LS060T1SX01 6.0" FullHD panel
using NT35695 driver. This panel can be found i.e. in the Dragonboard
Display Adapter bundle.
Marek Vasut [Sun, 10 Oct 2021 14:49:19 +0000 (16:49 +0200)]
drm/bridge: lvds-codec: Add support for LVDS data mapping select
Decoder input LVDS format is a property of the decoder chip or even
its strapping. Handle data-mapping the same way lvds-panel does. In
case data-mapping is not present, do nothing, since there are still
legacy bindings which do not specify this property.
Marek Vasut [Sun, 10 Oct 2021 14:49:18 +0000 (16:49 +0200)]
dt-bindings: display: bridge: lvds-codec: Document LVDS data mapping select
Decoder input LVDS format is a property of the decoder chip or even
its strapping. Add DT property data-mapping the same way lvds-panel
does, to define the LVDS data mapping.
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Marek Vasut <marex@denx.de> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Cc: Rob Herring <robh+dt@kernel.org> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: devicetree@vger.kernel.org
To: dri-devel@lists.freedesktop.org Signed-off-by: Sam Ravnborg <sam@ravnborg.org> Link: https://patchwork.freedesktop.org/patch/msgid/20211010144919.38392-1-marex@denx.de
drm/panel: Add support for Sharp LS060T1SX01 panel
Add driver to support Sharp LS06T1SX01 FullHD panel. The panel uses
nt35695 driver IC. For example this LCD module can be found in the
kwaek.ca Dragonboard Display Adapter Bundle.
dt-bindings: add bindings for the Sharp LS060T1SX01 panel
Add devicetree bindings for the Sharp LS060T1SX01 6.0" FullHD panel
using NT35695 driver. This panel can be found i.e. in the Dragonboard
Display Adapter bundle.
David Heidelberg [Mon, 27 Sep 2021 21:45:03 +0000 (23:45 +0200)]
dt-bindings: display: simple: hardware can use ddc-i2c-bus
Both hardware and driver can communicate DDC over i2c bus.
Fixes warnings as:
arch/arm/boot/dts/tegra20-paz00.dt.yaml: panel: 'ddc-i2c-bus' does not match any of the regexes: 'pinctrl-[0-9]+'
From schema: /home/runner/work/linux/linux/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
This tablet display is unique and hence must be added to documentation.
Unfortunately, it's real make and number is not known due to obscure and
missing documentation and lack of writing on the display assembly
itself.
So the natural alternative that came to mind is to name the panel after
the device that contained it (an Android tablet). Hopefully that isn't
an issue.
I can confirm that the parameters that I've obtained are correct since
they came from a dump of the original Android OS.
dp-aux-bus.yaml says we can list an eDP panel as a child of
an eDP controller node to represent the fact that the panel
is connected to the controller's DP AUX bus.
Move detach implementation from sn65dsi83_remove() to dedicated
.detach callback. There is no functional change to the code, but
that detach is now in the correct location.
Signed-off-by: Marek Vasut <marex@denx.de> Cc: Jagan Teki <jagan@amarulasolutions.com> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Cc: Linus Walleij <linus.walleij@linaro.org> Cc: Robert Foss <robert.foss@linaro.org> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: dri-devel@lists.freedesktop.org Reviewed-by: Robert Foss <robert.foss@linaro.org> Signed-off-by: Robert Foss <robert.foss@linaro.org> Link: https://patchwork.freedesktop.org/patch/msgid/20210907024038.871299-1-marex@denx.de
Simon Ser [Mon, 4 Oct 2021 09:12:50 +0000 (09:12 +0000)]
drm/connector: refer to CTA-861-G in the "content type" prop docs
The KMS documentation doesn't say much about the meaning of each
content type. Add a reference to the specification defining them.
Signed-off-by: Simon Ser <contact@emersion.fr> Cc: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Jani Nikula <jani.nikula@linux.intel.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.com> Link: https://patchwork.freedesktop.org/patch/msgid/20211004091236.82010-1-contact@emersion.fr
drivers/gpu/drm/drm_plane_helper.c: In function 'drm_primary_helper_update':
drivers/gpu/drm/drm_plane_helper.c:113:32: error: 'visible' is used uninitialized [-Werror=uninitialized]
113 | struct drm_plane_state plane_state = {
| ^~~~~~~~~~~
drivers/gpu/drm/drm_plane_helper.c:178:14: note: 'visible' was declared here
178 | bool visible;
| ^~~~~~~
cc1: all warnings being treated as errors
visible is an output, not an input. in practice this use might turn out
OK but it's still UB.
Cai Huoqing [Wed, 22 Sep 2021 12:59:08 +0000 (20:59 +0800)]
drm/bridge: dw-hdmi-cec: Make use of the helper function devm_add_action_or_reset()
The helper function devm_add_action_or_reset() will internally
call devm_add_action(), and if devm_add_action() fails then it will
execute the action mentioned and return the error code. So
use devm_add_action_or_reset() instead of devm_add_action()
to simplify the error handling, reduce the code.
Christian König [Tue, 15 Jun 2021 13:10:03 +0000 (15:10 +0200)]
dma-buf: add dma_resv_for_each_fence_unlocked v8
Abstract the complexity of iterating over all the fences
in a dma_resv object.
The new loop handles the whole RCU and retry dance and
returns only fences where we can be sure we grabbed the
right one.
v2: fix accessing the shared fences while they might be freed,
improve kerneldoc, rename _cursor to _iter, add
dma_resv_iter_is_exclusive, add dma_resv_iter_begin/end
v3: restructor the code, move rcu_read_lock()/unlock() into the
iterator, add dma_resv_iter_is_restarted()
v4: fix NULL deref when no explicit fence exists, drop superflous
rcu_read_lock()/unlock() calls.
v5: fix typos in the documentation
v6: fix coding error when excl fence is NULL
v7: one more logic fix
v8: fix index check in dma_resv_iter_is_exclusive()
In the commit 1428c594df89 ("drm/edid: Break out reading block 0 of
the EDID") I broke out reading the base block of the EDID to its own
function. Unfortunately, when I did that I messed up the handling when
drm_edid_is_zero() indicated that we had an EDID that was all 0x00 or
when we went through 4 loops and didn't get a valid EDID. Specifically
I needed to pass the broken EDID to connector_bad_edid() but now I was
passing an error-pointer.
Let's re-jigger things so we can pass the bad EDID in properly.
Fixes: 1428c594df89 ("drm/edid: Break out reading block 0 of the EDID") Reported-by: kernel test robot <oliver.sang@intel.com> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Link: https://patchwork.freedesktop.org/patch/msgid/20211004092100.1.Ic90a5ebd44c75db963112be167a03cc96f9fb249@changeid
Using the generic extension from the previous patch, a specific multisync
extension enables more than one in/out binary syncobj per job submission.
Arrays of syncobjs are set in struct drm_v3d_multisync, that also cares
of determining the stage for sync (wait deps) according to the job
queue.
v2:
- subclass the generic extension struct (Daniel)
- simplify adding dependency conditions to make understandable (Iago)
v3:
- fix conditions to consider single or multiples in/out_syncs (Iago)
- remove irrelevant comment (Iago)
Add support to attach generic extensions on job submission. This patch
is third prep work to enable multiple syncobjs on job submission. With
this work, when the job submission interface needs to be extended to
accommodate a new feature, we will use a generic extension struct where
an id determines the data type to be pointed. The first application is
to enable multiples in/out syncobj (next patch), but the base is
already done for future features. Therefore, to attach a new feature,
a specific extension struct should subclass drm_v3d_extension and
update the list of extensions in a job submission.
v2:
- remove redundant elements to subclass struct (Daniel)
Move job memory allocation to v3d_job_init function. This aim to facilitate
error handling in job initialization, since cleanup steps are similar for
all (struct v3d_job)-based types of job involved in a command submission.
To generalize v3d_job_init(), this change takes into account that all job
structs have the first element a struct v3d_job (bin, render, tfu, csd) or
it is a v3d_job itself (clean_job) for pointer casting.
v3:
- explicitly init job as NULL (Iago)
- fix pm failure handling on v3_job_init (Iago)
drm/v3d: decouple adding job dependencies steps from job init
Prep work to enable a job to wait for more than one syncobj before
start. Also get rid of old checkpatch warnings in the v3d_gem file.
No functional changes.
For the brave new world of bridges not creating their own connectors, we
need to implement the max clock limitation via bridge->mode_valid()
instead of connector->mode_valid().
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
Fernando Ramos [Fri, 24 Sep 2021 06:43:20 +0000 (08:43 +0200)]
drm/i915: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN() part 2
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
While the previous commit was a simple "search and replace", this time I
had to do a bit of refactoring as only one call to
DRM_MODESET_LOCK_ALL_BEGIN() is allowed inside one same function.
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace the boilerplate code
surrounding drm_modeset_lock_all_ctx() with DRM_MODESET_LOCK_ALL_BEGIN()
and DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace the boilerplate code
surrounding drm_modeset_lock_all_ctx() with DRM_MODESET_LOCK_ALL_BEGIN()
and DRM_MODESET_LOCK_ALL_END()
As requested in Documentation/gpu/todo.rst, replace the boilerplate code
surrounding drm_modeset_lock_all_ctx() with DRM_MODESET_LOCK_ALL_BEGIN()
and DRM_MODESET_LOCK_ALL_END()
Simon Ser [Fri, 3 Sep 2021 13:00:32 +0000 (13:00 +0000)]
drm/lease: allow empty leases
This can be used to create a separate DRM file description, thus
creating a new GEM handle namespace.
My use-case is wlroots. The library splits responsibilities between
separate components: the GBM allocator creates buffers, the GLES2
renderer uses EGL to import them and render to them, the DRM
backend imports the buffers and displays them. wlroots has a
modular architecture, and any of these components can be swapped
and replaced with something else. For instance, the pipeline can
be set up so that the DRM dumb buffer allocator is used instead of
GBM and the Pixman renderer is used instead of GLES2. Library users
can also replace any of these components with their own custom one.
DMA-BUFs are used to pass buffer references across components. We
could use GEM handles instead, but this would result in pain if
multiple GPUs are in use: wlroots copies buffers across GPUs as
needed. Importing a GEM handle created on one GPU into a completely
different GPU will blow up (fail at best, mix unrelated buffers
otherwise).
Everything is fine if all components use Mesa. However, this isn't
always desirable. For instance when running with DRM dumb buffers
and the Pixman software renderer it's unfortunate to depend on GBM
in the DRM backend just to turn DMA-BUFs into FB IDs. GBM loads
Mesa drivers to perform an action which has nothing driver-specific.
Additionally, drivers will fail the import if the 3D engine can't
use the imported buffer, for instance amdgpu will refuse to import
DRM dumb buffers [1]. We might also want to be running with a Vulkan
renderer and a Vulkan allocator in the future, and GBM wouldn't be
welcome in this setup.
To address this, GBM can be side-stepped in the DRM backend, and
can be replaced with drmPrimeFDToHandle calls. However because of
GEM handle reference counting issues, care must be taken to avoid
double-closing the same GEM handle. In particular, it's not
possible to share a DRM FD with GBM or EGL and perform some
drmPrimeFDToHandle calls manually.
So wlroots needs to re-open the DRM FD to create a new GEM handle
namespace. However there's no guarantee that the file-system
permissions will be set up so that the primary FD can be opened
by the compsoitor. On modern systems seatd or logind is a privileged
process responsible for doing this, and other processes aren't
expected to do it. For historical reasons systemd still allows
physically logged in users to open primary DRM nodes, but this
doesn't work on non-systemd setups and it's desirable to lock
them down at some point.
Some might suggest to open the render node instead of re-opening
the primary node. However some systems don't have a render node
at all (e.g. no GPU, or a split render/display SoC).
Solutions to this issue have been discussed in [2]. One solution
would be to open the magic /proc/self/fd/<fd> file, but it's a
Linux-specific hack (wlroots supports BSDs too). Another solution
is to add support for re-opening a DRM primary node to seatd/logind,
but they don't support it now and really haven't been designed for
this (logind would need to grow a completely new API, because it
assumes unique dev_t IDs). Also this seems like pushing down a
kernel limitation to user-space a bit too hard.
Another solution is to allow creating empty DRM leases. The lessee
FD would have its own GEM handle namespace, so wouldn't conflict
wth GBM/EGL. It would have the master bit set, but would be able
to manage zero resources. wlroots doesn't intend to share this FD
with any other process.
All in all IMHO that seems like a pretty reasonable solution to the
issue at hand.
Note, I've discussed with Jonas Ådahl and Mutter plans to adopt a
similar design in the future.
Example usage in wlroots is available at [3]. IGT test available
at [4].
Signed-off-by: Simon Ser <contact@emersion.fr> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Daniel Stone <daniels@collabora.com> Cc: Pekka Paalanen <pekka.paalanen@collabora.co.uk> Cc: Michel Dänzer <michel@daenzer.net> Cc: Emil Velikov <emil.l.velikov@gmail.com> Cc: Keith Packard <keithp@keithp.com> Cc: Boris Brezillon <boris.brezillon@collabora.com> Cc: Dave Airlie <airlied@redhat.com> Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com> Reviewed-by: Daniel Stone <daniels@collabora.com> Link: https://patchwork.freedesktop.org/patch/msgid/20210903130000.1590-2-contact@emersion.fr
Christian König [Tue, 15 Jun 2021 11:12:33 +0000 (13:12 +0200)]
dma-buf: fix and rework dma_buf_poll v7
Daniel pointed me towards this function and there are multiple obvious problems
in the implementation.
First of all the retry loop is not working as intended. In general the retry
makes only sense if you grab the reference first and then check the sequence
values.
Then we should always also wait for the exclusive fence.
It's also good practice to keep the reference around when installing callbacks
to fences you don't own.
And last the whole implementation was unnecessary complex and rather hard to
understand which could lead to probably unexpected behavior of the IOCTL.
Fix all this by reworking the implementation from scratch. Dropping the
whole RCU approach and taking the lock instead.
Only mildly tested and needs a thoughtful review of the code.
Pushing through drm-misc-next to avoid merge conflicts and give the code
another round of testing.
v2: fix the reference counting as well
v3: keep the excl fence handling as is for stable
v4: back to testing all fences, drop RCU
v5: handle in and out separately
v6: add missing clear of events
v7: change coding style as suggested by Michel, drop unused variables
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