linux/drivers/gpu/drm/i915/gt/intel_engine_pm.c
Chris Wilson 6c69a45445 drm/i915/gt: Mark context->active_count as protected by timeline->mutex
We use timeline->mutex to protect modifications to
context->active_count, and the associated enable/disable callbacks.
Due to complications with engine-pm barrier there is a path where we used
a "superlock" to provide serialised protect and so could not
unconditionally assert with lockdep that it was always held. However,
we can mark the mutex as taken (noting that we may be nested underneath
ourselves) which means we can be reassured the right timeline->mutex is
always treated as held and let lockdep roam free.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190816121000.8507-1-chris@chris-wilson.co.uk
2019-08-16 18:02:06 +01:00

154 lines
4.0 KiB
C

/*
* SPDX-License-Identifier: MIT
*
* Copyright © 2019 Intel Corporation
*/
#include "i915_drv.h"
#include "intel_engine.h"
#include "intel_engine_pm.h"
#include "intel_engine_pool.h"
#include "intel_gt.h"
#include "intel_gt_pm.h"
static int __engine_unpark(struct intel_wakeref *wf)
{
struct intel_engine_cs *engine =
container_of(wf, typeof(*engine), wakeref);
void *map;
GEM_TRACE("%s\n", engine->name);
intel_gt_pm_get(engine->gt);
/* Pin the default state for fast resets from atomic context. */
map = NULL;
if (engine->default_state)
map = i915_gem_object_pin_map(engine->default_state,
I915_MAP_WB);
if (!IS_ERR_OR_NULL(map))
engine->pinned_default_state = map;
if (engine->unpark)
engine->unpark(engine);
intel_engine_init_hangcheck(engine);
return 0;
}
static inline void __timeline_mark_lock(struct intel_context *ce)
{
mutex_acquire(&ce->timeline->mutex.dep_map, 2, 0, _THIS_IP_);
}
static inline void __timeline_mark_unlock(struct intel_context *ce)
{
mutex_release(&ce->timeline->mutex.dep_map, 0, _THIS_IP_);
}
static bool switch_to_kernel_context(struct intel_engine_cs *engine)
{
struct i915_request *rq;
/* Already inside the kernel context, safe to power down. */
if (engine->wakeref_serial == engine->serial)
return true;
/* GPU is pointing to the void, as good as in the kernel context. */
if (intel_gt_is_wedged(engine->gt))
return true;
/*
* Note, we do this without taking the timeline->mutex. We cannot
* as we may be called while retiring the kernel context and so
* already underneath the timeline->mutex. Instead we rely on the
* exclusive property of the __engine_park that prevents anyone
* else from creating a request on this engine. This also requires
* that the ring is empty and we avoid any waits while constructing
* the context, as they assume protection by the timeline->mutex.
* This should hold true as we can only park the engine after
* retiring the last request, thus all rings should be empty and
* all timelines idle.
*/
__timeline_mark_lock(engine->kernel_context);
rq = __i915_request_create(engine->kernel_context, GFP_NOWAIT);
if (IS_ERR(rq))
/* Context switch failed, hope for the best! Maybe reset? */
return true;
intel_timeline_enter(rq->timeline);
/* Check again on the next retirement. */
engine->wakeref_serial = engine->serial + 1;
i915_request_add_active_barriers(rq);
/* Install ourselves as a preemption barrier */
rq->sched.attr.priority = I915_PRIORITY_UNPREEMPTABLE;
__i915_request_commit(rq);
/* Release our exclusive hold on the engine */
__intel_wakeref_defer_park(&engine->wakeref);
__i915_request_queue(rq, NULL);
__timeline_mark_unlock(engine->kernel_context);
return false;
}
static int __engine_park(struct intel_wakeref *wf)
{
struct intel_engine_cs *engine =
container_of(wf, typeof(*engine), wakeref);
engine->saturated = 0;
/*
* If one and only one request is completed between pm events,
* we know that we are inside the kernel context and it is
* safe to power down. (We are paranoid in case that runtime
* suspend causes corruption to the active context image, and
* want to avoid that impacting userspace.)
*/
if (!switch_to_kernel_context(engine))
return -EBUSY;
GEM_TRACE("%s\n", engine->name);
intel_engine_disarm_breadcrumbs(engine);
intel_engine_pool_park(&engine->pool);
/* Must be reset upon idling, or we may miss the busy wakeup. */
GEM_BUG_ON(engine->execlists.queue_priority_hint != INT_MIN);
if (engine->park)
engine->park(engine);
if (engine->pinned_default_state) {
i915_gem_object_unpin_map(engine->default_state);
engine->pinned_default_state = NULL;
}
engine->execlists.no_priolist = false;
intel_gt_pm_put(engine->gt);
return 0;
}
static const struct intel_wakeref_ops wf_ops = {
.get = __engine_unpark,
.put = __engine_park,
};
void intel_engine_init__pm(struct intel_engine_cs *engine)
{
struct intel_runtime_pm *rpm = &engine->i915->runtime_pm;
intel_wakeref_init(&engine->wakeref, rpm, &wf_ops);
}
#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftest_engine_pm.c"
#endif