kernel/include/drm/drm_dp_mst_helper.h, branch linux-5.1.y

Merge v5.0-rc7 into drm-next

2019-02-18T03:27:15Z

Backmerging for nouveau and imx that needed some fixes for next pulls. Signed-off-by: Dave Airlie

drm/dp_mst: Start tracking per-port VCPI allocations

2019-01-11T01:42:13Z

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 Reviewed-by: Daniel Vetter Cc: David Airlie Cc: Jerry Zuo Cc: Harry Wentland Cc: Juston Li Link: https://patchwork.freedesktop.org/patch/msgid/20190111005343.17443-19-lyude@redhat.com

drm/dp_mst: Add some atomic state iterator macros

2019-01-11T01:38:38Z

Changes since v6: - Move EXPORT_SYMBOL() for drm_dp_mst_topology_state_funcs to this commit - Document __drm_dp_mst_state_iter_get() and note that it shouldn't be called directly Signed-off-by: Lyude Paul Reviewed-by: Daniel Vetter Cc: David Airlie Cc: Jerry Zuo Cc: Harry Wentland Cc: Juston Li Link: https://patchwork.freedesktop.org/patch/msgid/20190111005343.17443-18-lyude@redhat.com

drm/dp_mst: Introduce new refcounting scheme for mstbs and ports

2019-01-11T01:12:19Z

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 91a25e463130 ("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 263efde31f97 ("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 c54c7374ff44 ("drm/dp_mst: Skip validating ports during destruction, just ref") But then that introduced use-after-free errors, so I quickly reverted it: commit 9765635b3075 ("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 Reviewed-by: Harry Wentland Reviewed-by: Daniel Vetter Cc: David Airlie Cc: Jerry Zuo Cc: Juston Li Link: https://patchwork.freedesktop.org/patch/msgid/20190111005343.17443-7-lyude@redhat.com

drm/dp_mst: Add __must_check to drm_dp_mst_topology_mgr_resume()

2019-01-08T22:58:27Z

Since I've had to fix two cases of drivers not checking the return code from this function, let's make the compiler complain so this doesn't come up again in the future. Changes since v1: * Remove unneeded __must_check in function declaration - danvet Signed-off-by: Lyude Paul Cc: Jerry Zuo Reviewed-by: Daniel Vetter Reviewed-by: Harry Wentland Link: https://patchwork.freedesktop.org/patch/msgid/20190108211133.32564-4-lyude@redhat.com

drm/dp-mst-helper: Remove hotplug callback

2018-12-10T10:01:15Z

When everyone implements it exactly the same way, among all 4 implementations, there's not really a need to overwrite this at all. Aside: drm_kms_helper_hotplug_event is pretty much core functionality at this point. Probably should move it there. Reviewed-by: Lyude Paul Acked-by: Alex Deucher Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20181128221234.15054-1-daniel.vetter@ffwll.ch

drm/dp_mst: Remove all evil duplicate state pointers

2018-10-24T19:44:45Z

There's no reason to track the atomic state three times. Unfortunately, this is currently what we're doing, and even worse is that there is only one actually correct state pointer: the one in mst_state->base.state. mgr->state never seems to be used, along with the one in mst_state->state. This confused me for over 4 hours until I realized there was no magic behind these pointers. So, let's save everyone else from the trouble. Signed-off-by: Lyude Paul . Cc: Daniel Vetter Reviewed-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20181023231251.16883-3-lyude@redhat.com

drm/dp/mst: Sideband message transaction to power up/down nodes

2017-09-11T13:03:57Z

The POWER_DOWN_PHY and POWER_UP_PHY sideband message transactions allow the source to reqest any node in a mst path or a whole path to be powered down or up. This allows drivers to target a specific sink in the MST topology, an improvement over just power managing the imediate downstream device. Secondly, since the request-reply protocol waits for an ACK, we can be sure that a downstream sink has enough time to respond to a power up/down request. v2: Fix memory leak (Lyude) Cc: Lyude Cc: Ville Syrjälä Cc: Harry Wentland Signed-off-by: Dhinakaran Pandiyan Link: https://patchwork.freedesktop.org/patch/msgid/20170907001458.9399-1-dhinakaran.pandiyan@intel.com Reviewed-by: Lyude Paul Signed-off-by: Ville Syrjälä

drm/atomic: Make private objs proper objects

2017-07-13T16:28:43Z

Make the atomic private object stuff less special by introducing proper base classes for the object and its state. Drivers can embed these in their own appropriate objects, after which these things will work exactly like the plane/crtc/connector states during atomic operations. v2: Reorder to not depend on drm_dynarray (Daniel) Cc: Dhinakaran Pandiyan Cc: Daniel Vetter Reviewed-by: Daniel Vetter #v1 Signed-off-by: Ville Syrjälä Link: http://patchwork.freedesktop.org/patch/msgid/20170712155102.26276-3-ville.syrjala@linux.intel.com

drm/dp: Add DP MST helpers to atomically find and release vcpi slots

2017-05-04T13:02:47Z

drm_dp_atomic_find_vcpi_slots() should be called from ->atomic_check() to check there are sufficient vcpi slots for a mode and to add that to the state. This should be followed by a call to drm_dp_mst_allocate_vcpi() in ->atomic_commit() to initialize a struct vcpi for the port. drm_dp_atomic_release_vcpi_slots() should be called from ->atomic_check() to release a port's vcpi slot allocation from the state. Drivers that do not make use of this atomic helper are expected to call drm_dp_find_vcpi_slots() instead before calling drm_dp_mst_allocate_vcpi(). v3: drm_dp_atomic_release_vcpi_slots() now needs to know how many slots to release as we may not have a valid reference to port. v2: Added checks for verifying the port reference is valid Moved get_mst_topology_state() into the helpers (Daniel) Changed find_vcpi_slots() to not depend on current allocation Cc: Daniel Vetter Cc: Maarten Lankhorst Cc: Archit Taneja Cc: Chris Wilson Cc: Harry Wentland Reviewed-by: Harry Wentland Reviewed-by: Maarten Lankhorst Signed-off-by: Dhinakaran Pandiyan Signed-off-by: Maarten Lankhorst Link: http://patchwork.freedesktop.org/patch/msgid/1492753893-3748-4-git-send-email-dhinakaran.pandiyan@intel.com