From 5d266692372dfb412150006df420185b666658f9 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 23 Oct 2017 22:32:36 +0100
Subject: [PATCH] drm/i915: Filter out spurious execlists context-switch interrupts
Git-commit: 5d266692372dfb412150006df420185b666658f9
Patch-mainline: v4.15-rc1
References: FATE#322643 bsc#1055900
No-fix: 4a118ecbe99c93cf9f9582e83a88d03f18d6cb84
Back in commit a4b2b01523a8 ("drm/i915: Don't mark an execlists
context-switch when idle") we noticed the presence of late
context-switch interrupts. We were able to filter those out by looking
at whether the ELSP remained active, but in commit beecec901790
("drm/i915/execlists: Preemption!") that became problematic as we now
anticipate receiving a context-switch event for preemption while ELSP
may be empty. To restore the spurious interrupt suppression, add a
counter for the expected number of pending context-switches and skip if
we do not need to handle this interrupt to make forward progress.
V2: Don't forget to switch on for preempt.
V3: Reduce the counter to a on/off boolean tracker. Declare the HW as
active when we first submit, and idle after the final completion event
(with which we confirm the HW says it is idle), and track each source
of activity separately. With a finite number of sources, it should aide
us in debugging which gets stuck.
Fixes: beecec901790 ("drm/i915/execlists: Preemption!")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171023213237.26536-3-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
(cherry picked from commit 4a118ecbe99c93cf9f9582e83a88d03f18d6cb84)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/i915_guc_submission.c | 3 ++
drivers/gpu/drm/i915/i915_irq.c | 6 +++--
drivers/gpu/drm/i915/intel_engine_cs.c | 5 ++--
drivers/gpu/drm/i915/intel_lrc.c | 27 +++++++++++++++++------
drivers/gpu/drm/i915/intel_ringbuffer.h | 34 +++++++++++++++++++++++++++--
5 files changed, 62 insertions(+), 13 deletions(-)
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -610,6 +610,7 @@ done:
execlists->first = rb;
if (submit) {
port_assign(port, last);
+ execlists_set_active(execlists, EXECLISTS_ACTIVE_USER);
i915_guc_submit(engine);
}
spin_unlock_irq(&engine->timeline->lock);
@@ -633,6 +634,8 @@ static void i915_guc_irq_handler(unsigne
rq = port_request(&port[0]);
}
+ if (!rq)
+ execlists_clear_active(execlists, EXECLISTS_ACTIVE_USER);
if (!port_isset(last_port))
i915_guc_dequeue(engine);
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1388,8 +1388,10 @@ gen8_cs_irq_handler(struct intel_engine_
bool tasklet = false;
if (iir & (GT_CONTEXT_SWITCH_INTERRUPT << test_shift)) {
- __set_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
- tasklet = true;
+ if (READ_ONCE(engine->execlists.active)) {
+ __set_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
+ tasklet = true;
+ }
}
if (iir & (GT_RENDER_USER_INTERRUPT << test_shift)) {
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1548,8 +1548,8 @@ bool intel_engine_is_idle(struct intel_e
if (test_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted))
return false;
- /* Both ports drained, no more ELSP submission? */
- if (port_request(&engine->execlists.port[0]))
+ /* Waiting to drain ELSP? */
+ if (READ_ONCE(engine->execlists.active))
return false;
/* ELSP is empty, but there are ready requests? */
@@ -1749,6 +1749,7 @@ void intel_engine_dump(struct intel_engi
idx);
}
}
+ drm_printf(m, "\t\tHW active? 0x%x\n", execlists->active);
rcu_read_unlock();
} else if (INTEL_GEN(dev_priv) > 6) {
drm_printf(m, "\tPP_DIR_BASE: 0x%08x\n",
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -575,7 +575,8 @@ static void execlists_dequeue(struct int
* the state of the GPU is known (idle).
*/
inject_preempt_context(engine);
- execlists->preempt = true;
+ execlists_set_active(execlists,
+ EXECLISTS_ACTIVE_PREEMPT);
goto unlock;
} else {
/*
@@ -683,8 +684,10 @@ done:
unlock:
spin_unlock_irq(&engine->timeline->lock);
- if (submit)
+ if (submit) {
+ execlists_set_active(execlists, EXECLISTS_ACTIVE_USER);
execlists_submit_ports(engine);
+ }
}
static void
@@ -696,6 +699,7 @@ execlist_cancel_port_requests(struct int
while (num_ports-- && port_isset(port)) {
struct drm_i915_gem_request *rq = port_request(port);
+ GEM_BUG_ON(!execlists->active);
execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_PREEMPTED);
i915_gem_request_put(rq);
@@ -861,15 +865,21 @@ static void intel_lrc_irq_handler(unsign
unwind_incomplete_requests(engine);
spin_unlock_irq(&engine->timeline->lock);
- GEM_BUG_ON(!execlists->preempt);
- execlists->preempt = false;
+ GEM_BUG_ON(!execlists_is_active(execlists,
+ EXECLISTS_ACTIVE_PREEMPT));
+ execlists_clear_active(execlists,
+ EXECLISTS_ACTIVE_PREEMPT);
continue;
}
if (status & GEN8_CTX_STATUS_PREEMPTED &&
- execlists->preempt)
+ execlists_is_active(execlists,
+ EXECLISTS_ACTIVE_PREEMPT))
continue;
+ GEM_BUG_ON(!execlists_is_active(execlists,
+ EXECLISTS_ACTIVE_USER));
+
/* Check the context/desc id for this event matches */
GEM_DEBUG_BUG_ON(buf[2 * head + 1] != port->context_id);
@@ -892,6 +902,9 @@ static void intel_lrc_irq_handler(unsign
/* After the final element, the hw should be idle */
GEM_BUG_ON(port_count(port) == 0 &&
!(status & GEN8_CTX_STATUS_ACTIVE_IDLE));
+ if (port_count(port) == 0)
+ execlists_clear_active(execlists,
+ EXECLISTS_ACTIVE_USER);
}
if (head != execlists->csb_head) {
@@ -901,7 +914,7 @@ static void intel_lrc_irq_handler(unsign
}
}
- if (!execlists->preempt)
+ if (!execlists_is_active(execlists, EXECLISTS_ACTIVE_PREEMPT))
execlists_dequeue(engine);
intel_uncore_forcewake_put(dev_priv, execlists->fw_domains);
@@ -1460,7 +1473,7 @@ static int gen8_init_common_ring(struct
GT_CONTEXT_SWITCH_INTERRUPT << engine->irq_shift);
clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
execlists->csb_head = -1;
- execlists->preempt = false;
+ execlists->active = 0;
/* After a GPU reset, we may have requests to replay */
if (!i915_modparams.enable_guc_submission && execlists->first)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -241,9 +241,17 @@ struct intel_engine_execlists {
} port[EXECLIST_MAX_PORTS];
/**
- * @preempt: are we currently handling a preempting context switch?
+ * @active: is the HW active? We consider the HW as active after
+ * submitting any context for execution and until we have seen the
+ * last context completion event. After that, we do not expect any
+ * more events until we submit, and so can park the HW.
+ *
+ * As we have a small number of different sources from which we feed
+ * the HW, we track the state of each inside a single bitfield.
*/
- bool preempt;
+ unsigned int active;
+#define EXECLISTS_ACTIVE_USER 0
+#define EXECLISTS_ACTIVE_PREEMPT 1
/**
* @port_mask: number of execlist ports - 1
@@ -525,6 +533,27 @@ struct intel_engine_cs {
u32 (*get_cmd_length_mask)(u32 cmd_header);
};
+static inline void
+execlists_set_active(struct intel_engine_execlists *execlists,
+ unsigned int bit)
+{
+ __set_bit(bit, (unsigned long *)&execlists->active);
+}
+
+static inline void
+execlists_clear_active(struct intel_engine_execlists *execlists,
+ unsigned int bit)
+{
+ __clear_bit(bit, (unsigned long *)&execlists->active);
+}
+
+static inline bool
+execlists_is_active(const struct intel_engine_execlists *execlists,
+ unsigned int bit)
+{
+ return test_bit(bit, (unsigned long *)&execlists->active);
+}
+
static inline unsigned int
execlists_num_ports(const struct intel_engine_execlists * const execlists)
{
@@ -538,6 +567,7 @@ execlists_port_complete(struct intel_eng
const unsigned int m = execlists->port_mask;
GEM_BUG_ON(port_index(port, execlists) != 0);
+ GEM_BUG_ON(!execlists_is_active(execlists, EXECLISTS_ACTIVE_USER));
memmove(port, port + 1, m * sizeof(struct execlist_port));
memset(port + m, 0, sizeof(struct execlist_port));