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    drm/i915: Add support for per engine reset recovery · a1ef70e1
    Michel Thierry authored
    
    
    This change implements support for per-engine reset as an initial, less
    intrusive hang recovery option to be attempted before falling back to the
    legacy full GPU reset recovery mode if necessary. This is only supported
    from Gen8 onwards.
    
    Hangchecker determines which engines are hung and invokes error handler to
    recover from it. Error handler schedules recovery for each of those engines
    that are hung. The recovery procedure is as follows,
     - identifies the request that caused the hang and it is dropped
     - force engine to idle: this is done by issuing a reset request
     - reset the engine
     - re-init the engine to resume submissions.
    
    If engine reset fails then we fall back to heavy weight full gpu reset
    which resets all engines and reinitiazes complete state of HW and SW.
    
    v2: Rebase.
    v3: s/*engine_reset*/*reset_engine*/; freeze engine and irqs before
    calling i915_gem_reset_engine (Chris).
    v4: Rebase, modify i915_gem_reset_prepare to use a ring mask and
    reuse the function for reset_engine.
    v5: intel_reset_engine_start/cancel instead of request/unrequest_reset.
    v6: Clean up reset_engine function to not require mutex, i.e. no need to call
    revoke/restore_fences and _retire_requests (Chris).
    v7: Remove leftovers from v5, i.e. no need to disable irq, hold
    forcewake or wakeup the handoff bit (Chris).
    v8: engine_retire_requests should be (and it was) static; explain that
    we have to re-init the engine after reset, which is why the init_hw call
    is needed; check reset-in-progress flag (Chris).
    v9: Rebase, include code to pass the active request to gem_reset_engine
    (as it is already done in full reset). Remove unnecessary
    intel_reset_engine_start/cancel, these are executed as part of the
    reset.
    v10: Rebase, use the right I915_RESET_ENGINE flag.
    v11: Fixup to call reset_finish_engine even on error.
    
    Cc: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
    Signed-off-by: default avatarTomas Elf <tomas.elf@intel.com>
    Signed-off-by: default avatarArun Siluvery <arun.siluvery@linux.intel.com>
    Signed-off-by: default avatarMichel Thierry <michel.thierry@intel.com>
    Link: http://patchwork.freedesktop.org/patch/msgid/20170615201828.23144-6-michel.thierry@intel.com
    
    
    Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Link: http://patchwork.freedesktop.org/patch/msgid/20170620095751.13127-6-chris@chris-wilson.co.uk
    a1ef70e1