drm-misc-next for 5.1:
UAPI Changes:
Cross-subsystem Changes:
Core Changes:
- Split out some part of drm_crtc_helper.h into drm_probe_helper.h
- DRIVER_* flags improvements
- New tasks on the TODO-list
- Improvements to the documentation
Driver Changes:
- Continual of drmP.h removal in multiple drivers
- Removal of FBINFO_(FLAG_)DEFAULT in multiple drivers
- sun4i: Addition of the A23 support, multiple fixes for the tiled
formats
- atmel-hlcdc: Fix of clipping and rotation properties
- qxl: various BO-related improvements, prime and generic fbdev emulation
support
- dw-hdmi: Support for HDMI2.0 2160p modes and YUV420 output
- New Sitronix ST7701 panel driver
- New Kingdisplay KD097D04 panel driver
- New LeMaker BL035-RGB-002 panel driver
- New PDA 91-00156-A0 panel driver
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190201144749.t3abxvguhstu6bcl@flea
- Track all runtime-PM wakerefs and other rpm improvements (Chris)
- Fix ILK-IVB primary plane enable delays (Juha-Pekka)
- Differentiate between gtt->mutex and ppgtt->mutex (Chris)
- Prevent concurrent GGTT update and use on Braswell (Chris)
- Fix CNL macros for DDI vswing (Aditya)
- Fix static code analysis warning (RK)
- Only dump GPU state on set-wedged if interesting (Chris)
- Port F detection improvements (Imre)
- userptr mutex lock fixes (Chris)
- Fix on MST allocation by propagating error value at compute_config (Lyude)
- Serialise concurrent calls to set_wedge (Chris)
- Unify reset functionality into i915_reset.c (Chris)
- Switch to kernel fixed size types (Jani)
- Limit the for_each_set_bit to the valid range (Chris)
- Fix wakeref cooie handling (Tvrtko)
- IRQs handling improvements (Chris)
- Selftests improvements (Chris)
- Remove superfluous PANEL_POWER_OFF macro (Jani)
- Global seqno fix (Chris)
- DSI fixes (Hans)
- Refactor out intel_context_init() (Chris)
- Show all active engines on hangcheck (Chris)
- PSR2 fixes and improvements (Jose)
- Do a posting read after irq install on Ice Lake (Daniele)
- Add few more device IDs for Ice Lake (Rodrigo)
- Mark up priority boost on preemption (Chris)
- Add color management LUT validation helper (Matt)
- Split out intel_crt_present to platform specific setup (Jani)
- LVDS and TV clean up and improvements (Jani)
- Simplify CRT VBT check for per-VLV/DDI (Jani)
- De-inline intel_context_init() (Chris)
- Backlight fixes (Maarten)
- Enable fastset for non-boot modesets (Maarten)
- Make HW readout mark CRTC scaler as in use (Maarten)
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190128181000.GA5284@intel.com
New stuff for 5.1.
amdgpu:
- DC bandwidth formula updates
- Support for DCC on scanout surfaces
- Support for multiple IH rings on soc15 asics
- Fix xgmi locking
- Add sysfs interface to get pcie usage stats
- Simplify DC i2c/aux code
- Initial support for BACO on vega10/20
- New runtime SMU feature debug interface
- Expand existing sysfs power interfaces to new clock domains
- Handle kexec properly
- Simplify IH programming
- Rework doorbell handling across asics
- Drop old CI DPM implementation
- DC page flipping fixes
- Misc SR-IOV fixes
amdkfd:
- Simplify the interfaces between amdkfd and amdgpu
ttm:
- Add a callback to notify the driver when the lru changes
sched:
- Refactor mirror list handling
- Rework hw fence processing
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Alex Deucher <alexdeucher@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190125231517.26268-1-alexander.deucher@amd.com
This is only used by drm_irq_install(), which is an optional helper.
For legacy pci devices this is required (due to interrupt sharing without
msi/msi-x), and just making this the default exactly matches the behaviour
of all existing drivers using the drm_irq_install() helpers. In case that
ever becomes wrong drivers can roll their own irq handling, as many
drivers already do (for other reasons like needing a threaded interrupt
handler, or having an entire pile of different interrupt sources).
v2: Rebase
v3: Improve commit message (Emil)
Cc: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190129104248.26607-3-daniel.vetter@ffwll.ch
Expedite job deletion from ring mirror list to the HW fence signal
callback instead from finish_work, together with waiting for all
such fences to signal in drm_sched_stop we garantee that
already signaled job will not be processed twice.
Remove the sched finish fence callback and just submit finish_work
directly from the HW fence callback.
v2: Fix comments.
v3: Attach hw fence cb to sched_job
v5: Rebase
Suggested-by: Christian Koenig <Christian.Koenig@amd.com>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Decauple sched threads stop and start and ring mirror
list handling from the policy of what to do about the
guilty jobs.
When stoppping the sched thread and detaching sched fences
from non signaled HW fenes wait for all signaled HW fences
to complete before rerunning the jobs.
v2: Fix resubmission of guilty job into HW after refactoring.
v4:
Full restart for all the jobs, not only from guilty ring.
Extract karma increase into standalone function.
v5:
Rework waiting for signaled jobs without relying on the job
struct itself as those might already be freed for non 'guilty'
job's schedulers.
Expose karma increase to drivers.
v6:
Use list_for_each_entry_safe_continue and drm_sched_process_job
in case fence already signaled.
Call drm_sched_increase_karma only once for amdgpu and add documentation.
v7:
Wait only for the latest job's fence.
Suggested-by: Christian Koenig <Christian.Koenig@amd.com>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drm-misc-next for 5.1:
UAPI Changes:
- Addition of the Allwinner tiled format modifier
Cross-subsystem Changes:
Core Changes:
- dma-buf documentation improvements
- Removal of now unused fbdev helpers
- Addition of new drm fbdev helpers
- Improvements to tinydrm
- Addition of new drm_fourcc helpers
- Impromevents to i2c-over-aux to handle I2C_M_STOP
Driver Changes:
- Add support for the TI DS90C185 LVDS bridge
- Improvements to the thc63lvdm83d bridge
- Improvements to sun4i YUV and scaler support
- Fix to the powerdown sequence of panel-innolux
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190123110317.h4tovujaydo2bfz2@flea
- Unwind failure on pinning the gen7 PPGTT (Chris)
- Fastset updates to make sure DRRS and PSR are properly enabled (Hans)
- Header include clean-up (Brajeswar, Jani)
- Improvements and clean-up on debugfs (Chris, Jani)
- Avoid division by zero on CNL clocks setup (Xiao)
- Restrict PSMI context load w/a to Haswell GT1 (Chris)
- Remove HW semaphores for gen7 inter-engine sync (Chris)
- Pull the render flush into breadcrumb emission (Chris)
- i915_params copy and free helpers and other reorgs and docs (Jani)
- Remove has_pooled_eu static initializer (Tvrtko)
- Updates on kerneldoc (Chris)
- Remove redundant trailing request flush (Chris)
- ringbuffer irq seqno fixes and clean-up (Chris)
- splitting off runtime device info and other clean-up around (Jani)
- Selftests improvements (Chris, Daniele)
- Flush RING_IMR changes before changing the global GT IMR on gen6 and HSW (Chris)
- Some improvements and fixes around GPU reset and GPU hang report (Chris)
- Remove partial attempt to swizzle on pread/pwrite (Chris)
- Return immediately if trylock fails for direct-reclaim (Chris)
- Downgrade scare message for unknown HuC firmware (Jani)
- ACPI / PMIC for MIPI / DSI (Hans)
- Reduce i915_request_alloc retirement to local context (Chris)
- Init per-engine WAs for all engines (Daniele)
- drop DPF code for gen8+ (Daniele)
- Guard error capture against unpinned vma (Chris)
- Use mutex_lock_killable from inside the shrinker (Chris)
- Removing pooling from struct_mutex from vmap shrinker (Chris)
Signed-off-by: Dave Airlie <airlied@redhat.com>
# gpg: Signature made Fri 11 Jan 2019 09:58:18 AEST
# gpg: using RSA key FA625F640EEB13CA
# gpg: Good signature from "Rodrigo Vivi <rodrigo.vivi@intel.com>"
# gpg: aka "Rodrigo Vivi <rodrigo.vivi@gmail.com>"
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg: There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 6D20 7068 EEDD 6509 1C2C E2A3 FA62 5F64 0EEB 13CA
# Conflicts:
# drivers/gpu/drm/i915/intel_dp.c
# drivers/gpu/drm/i915/intel_drv.h
From: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190114183820.GA2855@intel.com
Some hardware may place additional restrictions on the gamma/degamma
curves described by our LUT properties. E.g., that a gamma curve never
decreases or that the red/green/blue channels of a LUT's entries must be
equal. Let's add a helper function that drivers can use to test that a
userspace-provided LUT is valid and doesn't violate hardware
requirements.
v2:
- Combine into a single helper that just takes a bitmask of the tests
to apply. (Brian Starkey)
- Add additional check (always performed) that LUT property blob size
is always a multiple of the LUT entry size. (stolen from ARM driver)
v3:
- Drop the LUT size check again since
drm_atomic_replace_property_blob_from_id() already covers this for
us. (Alexandru Gheorghe)
v4:
- Use an enum to describe possible test values rather than #define's;
this is cleaner to provide kerneldoc for. (Daniel Vetter)
- s/DRM_COLOR_LUT_INCREASING/DRM_COLOR_LUT_NON_DECREASING/. (Ville)
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Swati Sharma <swati2.sharma@intel.com>
Cc: Brian Starkey <Brian.Starkey@arm.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Reviewed-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181217224415.12848-1-matthew.d.roper@intel.com
It is often useful to check whether the DRM format info retrieved from
the DRM framebuffer matches a specific YUV planes disposition.
This introduces helpers to quickly check that a provided format info
matches a YUV format with a specific disposition, in commonly-used
terminology.
The intent of providing helpers taking the format info instead of the
fourcc alone is to avoid the overhead of iterating through all formats
when the whole format info structure is available. As a result, these
helpers are very simple so they are made inline.
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Reviewed-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190118145133.21281-2-paul.kocialkowski@bootlin.com
drm-misc-next for 5.1:
UAPI Changes:
- New fourcc identifier for ARM Framebuffer Compression v1.3
Cross-subsystem Changes:
Core Changes:
- Reorganisation of drm_device and drm_framebuffer headers
- Cleanup of the drmP inclusion
- Fix leaks in the fb-helpers
- Allow for depth different from bpp in fb-helper fbdev emulation
- Remove drm_mode_object from drm_display_mode
Driver Changes:
- Add reflection properties to rockchip
- a bunch of fixes for virtio
- a bunch of fixes for dp_mst and drivers using it, and introduction of a
new refcounting scheme
- Convertion of bochs to atomic and generic fbdev emulation
- Allow meson to remove the firmware framebuffers
[airlied: patch rcar-du to add drm_modes.h]
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190116200428.u2n4jbk4mzza7n6e@flea
This switches to drm_atomic_helper_dirtyfb() as the framebuffer dirty
handler. All flushing will now happen in the pipe functions.
Also enable the damage plane property for all except repaper which can
only do full updates.
ili9225:
This change made ili9225_init() equal to mipi_dbi_init() so use it.
v3: Include vblank header (Sam)
ili9225 and st7586 can't use mipi_dbi_enable_flush() (David)
v2: Remove fb check in mipi_dbi_enable_flush() it can't be NULL
(kbuild test robot)
Cc: David Lechner <david@lechnology.com>
Cc: Eric Anholt <eric@anholt.net>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: David Lechner <david@lechnology.com>
Reviewed-by: David Lechner <david@lechnology.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190115043643.2364-5-noralf@tronnes.org
0-DAY reported the following bug:
tree: git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
head: 21376e2c3c
commit: e9eafcb589 [1/2] drm: move drm_can_sleep() to drm_util.h
config: alpha-allmodconfig (attached as .config)
...
In file included from include/linux/irqflags.h:16:0,
from include/drm/drm_util.h:35,
from drivers/gpu/drm/qxl/qxl_cmd.c:28:
>> arch/alpha/include/asm/irqflags.h:58:15: error: unknown type name 'bool'
static inline bool arch_irqs_disabled_flags(unsigned long flags)
^~~~
And later following bug:
tree: git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
head: 21376e2c3c
commit: e9eafcb589 [1/2] drm: move drm_can_sleep() to drm_util.h
config: ia64-allyesconfig (attached as .config)
...
In file included from arch/ia64/include/asm/irqflags.h:14,
from include/linux/irqflags.h:16,
from include/drm/drm_util.h:35,
from drivers/gpu/drm/qxl/qxl_cmd.c:28:
arch/ia64/include/asm/pal.h: In function 'ia64_pal_tr_read':
arch/ia64/include/asm/pal.h:1703:64: error: implicit declaration of function 'ia64_tpa'; did you mean 'ia64_pal'? [-Werror=implicit-function-declaration]
PAL_CALL_PHYS_STK(iprv, PAL_VM_TR_READ, reg_num, tr_type,(u64)ia64_tpa(tr_buffer));
^~~~~~~~
...
So we have a situation where we do not pull in <linux/types.h>
when building for alpha and for ia64 we need even more definitions
are required.
Two invasive fixes where considered:
- Change all declarations of arch_irqs_disabled_flags() to use bool
- Add include of <linux/types.h> to all files that uses bool for
arch_irqs_disabled_flags
To invasive with a too high pain/benefit ratio, so dropped.
They would not cover ia64 either.
Some less invasive fixes was also considered:
- Add include of <linux/types.h> to drm_util.h
- Add include of <linux/interrupt.h> to drm_util.h
The first was dropped as this did not cover the ia64 case.
The latter was considered the best option as there could
be other similar cases and we would like the header files below
include/drm/ to be selfcontained.
So we end up pulling in a lot of stuff not needed, but this is
the price we pay in drm/ because the kernel headers are not all
selfcontained.
While at it, ordred the includefiles in drm_util in alphabetical order.
Build tested with alpha,ia64,arm,x86 with allmodconfig and allyesconfig.
v2:
- fix ia64 build, changed to include interrupt.h
- sort include files alphabetically
Fixes: 733748ac37b45 ("drm: move drm_can_sleep() to drm_util.h")
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190115214845.8117-1-sam@ravnborg.org
On i965gm we need to adjust max_vblank_count dynamically
depending on whether the TV encoder is used or not. To
that end add a per-crtc max_vblank_count that takes
precedence over its device wide counterpart. The driver
can now call drm_crtc_set_max_vblank_count() to configure
the per-crtc value before calling drm_vblank_on().
Also looks like there was some discussion about exynos needing
similar treatment.
v2: Drop the extra max_vblank_count!=0 check for the
WARN(last!=current), will take care of it in i915 code (Daniel)
WARN_ON(!inmodeset) (Daniel)
WARN_ON(dev->max_vblank_count)
Pimp up the docs (Daniel)
Cc: stable@vger.kernel.org
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181127182004.28885-1-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
The mode and ajusted_mode passed to the bridge .mode_set() operation
should never be modified by the bridge (and are not in any of the
existing bridge drivers). Make them const to make this clear.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
drm-next has been forwarded to 5.0-rc1, and we need it to apply the damage
helper for dirtyfb series from Noralf Trønnes.
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
There has been a TODO waiting for quite a long time in
drm_dp_mst_topology.c:
/* We cannot rely on port->vcpi.num_slots to update
* topology_state->avail_slots as the port may not exist if the parent
* branch device was unplugged. This should be fixed by tracking
* per-port slot allocation in drm_dp_mst_topology_state instead of
* depending on the caller to tell us how many slots to release.
*/
That's not the only reason we should fix this: forcing the driver to
track the VCPI allocations throughout a state's atomic check is
error prone, because it means that extra care has to be taken with the
order that drm_dp_atomic_find_vcpi_slots() and
drm_dp_atomic_release_vcpi_slots() are called in in order to ensure
idempotency. Currently the only driver actually using these helpers,
i915, doesn't even do this correctly: multiple ->best_encoder() checks
with i915's current implementation would not be idempotent and would
over-allocate VCPI slots, something I learned trying to implement
fallback retraining in MST.
So: simplify this whole mess, and teach drm_dp_atomic_find_vcpi_slots()
and drm_dp_atomic_release_vcpi_slots() to track the VCPI allocations for
each port. This allows us to ensure idempotency without having to rely
on the driver as much. Additionally: the driver doesn't need to do any
kind of VCPI slot tracking anymore if it doesn't need it for it's own
internal state.
Additionally; this adds a new drm_dp_mst_atomic_check() helper which
must be used by atomic drivers to perform validity checks for the new
VCPI allocations incurred by a state.
Also: update the documentation and make it more obvious that these
/must/ be called by /all/ atomic drivers supporting MST.
Changes since v9:
* Add some missing changes that were requested by danvet that I forgot
about after I redid all of the kref stuff:
* Remove unnecessary state changes in intel_dp_mst_atomic_check
* Cleanup atomic check logic for VCPI allocations - all we need to check in
compute_config is whether or not this state disables a CRTC, then free
VCPI based off that
Changes since v8:
* Fix compile errors, whoops!
Changes since v7:
- Don't check for mixed stale/valid VCPI allocations, just rely on
connector registration to stop such erroneous modesets
Changes since v6:
- Keep a kref to all of the ports we have allocations on. This required
a good bit of changing to when we call drm_dp_find_vcpi_slots(),
mainly that we need to ensure that we only redo VCPI allocations on
actual mode or CRTC changes, not crtc_state->active changes.
Additionally, we no longer take the registration of the DRM connector
for each port into account because so long as we have a kref to the
port in the new or previous atomic state, the connector will stay
registered.
- Use the small changes to drm_dp_put_port() to add even more error
checking to make misusage of the helpers more obvious. I added this
after having to chase down various use-after-free conditions that
started popping up from the new helpers so no one else has to
troubleshoot that.
- Move some accidental DRM_DEBUG_KMS() calls to DRM_DEBUG_ATOMIC()
- Update documentation again, note that find/release() should both not be
called on the same port in a single atomic check phase (but multiple
calls to one or the other is OK)
Changes since v4:
- Don't skip the atomic checks for VCPI allocations if no new VCPI
allocations happen in a state. This makes the next change I'm about
to list here a lot easier to implement.
- Don't ignore VCPI allocations on destroyed ports, instead ensure that
when ports are destroyed and still have VCPI allocations in the
topology state, the only state changes allowed are releasing said
ports' VCPI. This prevents a state with a mix of VCPI allocations
from destroyed ports, and allocations from valid ports.
Changes since v3:
- Don't release VCPI allocations in the topology state immediately in
drm_dp_atomic_release_vcpi_slots(), instead mark them as 0 and skip
over them in drm_dp_mst_duplicate_state(). This makes it so
drm_dp_atomic_release_vcpi_slots() is still idempotent while also
throwing warnings if the driver messes up it's book keeping and tries
to release VCPI slots on a port that doesn't have any pre-existing
VCPI allocation - danvet
- Change mst_state/state in some debugging messages to "mst state"
Changes since v2:
- Use kmemdup() for duplicating MST state - danvet
- Move port validation out of duplicate state callback - danvet
- Handle looping through MST topology states in
drm_dp_mst_atomic_check() so the driver doesn't have to do it
- Fix documentation in drm_dp_atomic_find_vcpi_slots()
- Move the atomic check for each individual topology state into it's
own function, reduces indenting
- Don't consider "stale" MST ports when calculating the bandwidth
requirements. This is needed because originally we relied on the
state duplication functions to prune any stale ports from the new
state, which would prevent us from incorrectly considering their
bandwidth requirements alongside legitimate new payloads.
- Add function references in drm_dp_atomic_release_vcpi_slots() - danvet
- Annotate atomic VCPI and atomic check functions with __must_check
- danvet
Changes since v1:
- Don't use the now-removed ->atomic_check() for private objects hook,
just give drivers a function to call themselves
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@redhat.com>
Cc: Jerry Zuo <Jerry.Zuo@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Juston Li <juston.li@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190111005343.17443-19-lyude@redhat.com
The current way of handling refcounting in the DP MST helpers is really
confusing and probably just plain wrong because it's been hacked up many
times over the years without anyone actually going over the code and
seeing if things could be simplified.
To the best of my understanding, the current scheme works like this:
drm_dp_mst_port and drm_dp_mst_branch both have a single refcount. When
this refcount hits 0 for either of the two, they're removed from the
topology state, but not immediately freed. Both ports and branch devices
will reinitialize their kref once it's hit 0 before actually destroying
themselves. The intended purpose behind this is so that we can avoid
problems like not being able to free a remote payload that might still
be active, due to us having removed all of the port/branch device
structures in memory, as per:
commit 91a25e4631 ("drm/dp/mst: deallocate payload on port destruction")
Which may have worked, but then it caused use-after-free errors. Being
new to MST at the time, I tried fixing it;
commit 263efde31f ("drm/dp/mst: Get validated port ref in drm_dp_update_payload_part1()")
But, that was broken: both drm_dp_mst_port and drm_dp_mst_branch structs
are validated in almost every DP MST helper function. Simply put, this
means we go through the topology and try to see if the given
drm_dp_mst_branch or drm_dp_mst_port is still attached to something
before trying to use it in order to avoid dereferencing freed memory
(something that has happened a LOT in the past with this library).
Because of this it doesn't actually matter whether or not we keep keep
the ports and branches around in memory as that's not enough, because
any function that validates the branches and ports passed to it will
still reject them anyway since they're no longer in the topology
structure. So, use-after-free errors were fixed but payload deallocation
was completely broken.
Two years later, AMD informed me about this issue and I attempted to
come up with a temporary fix, pending a long-overdue cleanup of this
library:
commit c54c7374ff ("drm/dp_mst: Skip validating ports during destruction, just ref")
But then that introduced use-after-free errors, so I quickly reverted
it:
commit 9765635b30 ("Revert "drm/dp_mst: Skip validating ports during destruction, just ref"")
And in the process, learned that there is just no simple fix for this:
the design is just broken. Unfortunately, the usage of these helpers are
quite broken as well. Some drivers like i915 have been smart enough to
avoid accessing any kind of information from MST port structures, but
others like nouveau have assumed, understandably so, that
drm_dp_mst_port structures are normal and can just be accessed at any
time without worrying about use-after-free errors.
After a lot of discussion, me and Daniel Vetter came up with a better
idea to replace all of this.
To summarize, since this is documented far more indepth in the
documentation this patch introduces, we make it so that drm_dp_mst_port
and drm_dp_mst_branch structures have two different classes of
refcounts: topology_kref, and malloc_kref. topology_kref corresponds to
the lifetime of the given drm_dp_mst_port or drm_dp_mst_branch in it's
given topology. Once it hits zero, any associated connectors are removed
and the branch or port can no longer be validated. malloc_kref
corresponds to the lifetime of the memory allocation for the actual
structure, and will always be non-zero so long as the topology_kref is
non-zero. This gives us a way to allow callers to hold onto port and
branch device structures past their topology lifetime, and dramatically
simplifies the lifetimes of both structures. This also finally fixes the
port deallocation problem, properly.
Additionally: since this now means that we can keep ports and branch
devices allocated in memory for however long we need, we no longer need
a significant amount of the port validation that we currently do.
Additionally, there is one last scenario that this fixes, which couldn't
have been fixed properly beforehand:
- CPU1 unrefs port from topology (refcount 1->0)
- CPU2 refs port in topology(refcount 0->1)
Since we now can guarantee memory safety for ports and branches
as-needed, we also can make our main reference counting functions fix
this problem by using kref_get_unless_zero() internally so that topology
refcounts can only ever reach 0 once.
Changes since v4:
* Change the kernel-figure summary for dp-mst/topology-figure-1.dot a
bit - danvet
* Remove figure numbers - danvet
Changes since v3:
* Remove rebase detritus - danvet
* Split out purely style changes into separate patches - hwentlan
Changes since v2:
* Fix commit message - checkpatch
* s/)-1/) - 1/g - checkpatch
Changes since v1:
* Remove forward declarations - danvet
* Move "Branch device and port refcounting" section from documentation
into kernel-doc comments - danvet
* Export internal topology lifetime functions into their own section in
the kernel-docs - danvet
* s/@/&/g for struct references in kernel-docs - danvet
* Drop the "when they are no longer being used" bits from the kernel
docs - danvet
* Modify diagrams to show how the DRM driver interacts with the topology
and payloads - danvet
* Make suggested documentation changes for
drm_dp_mst_topology_get_mstb() and drm_dp_mst_topology_get_port() -
danvet
* Better explain the relationship between malloc refs and topology krefs
in the documentation for drm_dp_mst_topology_get_port() and
drm_dp_mst_topology_get_mstb() - danvet
* Fix "See also" in drm_dp_mst_topology_get_mstb() - danvet
* Rename drm_dp_mst_topology_get_(port|mstb)() ->
drm_dp_mst_topology_try_get_(port|mstb)() and
drm_dp_mst_topology_ref_(port|mstb)() ->
drm_dp_mst_topology_get_(port|mstb)() - danvet
* s/should/must in docs - danvet
* WARN_ON(refcount == 0) in topology_get_(mstb|port) - danvet
* Move kdocs for mstb/port structs inline - danvet
* Split drm_dp_get_last_connected_port_and_mstb() changes into their own
commit - danvet
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@redhat.com>
Cc: Jerry Zuo <Jerry.Zuo@amd.com>
Cc: Juston Li <juston.li@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190111005343.17443-7-lyude@redhat.com
