[Intel-gfx] [PATCH v2] drm/i915/execlists: Process one CSB update at a time
Chris Wilson
chris at chris-wilson.co.uk
Wed Jun 27 10:43:14 UTC 2018
In the next patch, we will process the CSB events directly from the
submission path, rather than only after a CS interrupt. Hence, we will
no longer have the need for a loop until the has-interrupt bit is clear,
and in the meantime can remove that small optimisation.
v2: Tvrtko pointed out it was safer to unconditionally kick the tasklet
after each irq, when assuming that the tasklet is called for each irq.
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com> #v1
---
drivers/gpu/drm/i915/i915_irq.c | 7 +-
drivers/gpu/drm/i915/intel_lrc.c | 278 +++++++++++++++----------------
2 files changed, 141 insertions(+), 144 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 46aaef5c1851..d02f30591c0b 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1473,9 +1473,10 @@ gen8_cs_irq_handler(struct intel_engine_cs *engine, u32 iir)
bool tasklet = false;
if (iir & GT_CONTEXT_SWITCH_INTERRUPT) {
- if (READ_ONCE(engine->execlists.active))
- tasklet = !test_and_set_bit(ENGINE_IRQ_EXECLIST,
- &engine->irq_posted);
+ if (READ_ONCE(engine->execlists.active)) {
+ set_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
+ tasklet = true;
+ }
}
if (iir & GT_RENDER_USER_INTERRUPT) {
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 4b31e8f42aeb..91656eb2f2db 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -954,166 +954,162 @@ static void process_csb(struct intel_engine_cs *engine)
struct intel_engine_execlists * const execlists = &engine->execlists;
struct execlist_port *port = execlists->port;
struct drm_i915_private *i915 = engine->i915;
+
+ /* The HWSP contains a (cacheable) mirror of the CSB */
+ const u32 *buf =
+ &engine->status_page.page_addr[I915_HWS_CSB_BUF0_INDEX];
+ unsigned int head, tail;
bool fw = false;
- do {
- /* The HWSP contains a (cacheable) mirror of the CSB */
- const u32 *buf =
- &engine->status_page.page_addr[I915_HWS_CSB_BUF0_INDEX];
- unsigned int head, tail;
-
- /* Clear before reading to catch new interrupts */
- clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
- smp_mb__after_atomic();
-
- if (unlikely(execlists->csb_use_mmio)) {
- if (!fw) {
- intel_uncore_forcewake_get(i915, execlists->fw_domains);
- fw = true;
- }
+ /* Clear before reading to catch new interrupts */
+ clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
+ smp_mb__after_atomic();
- buf = (u32 * __force)
- (i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_BUF_LO(engine, 0)));
+ if (unlikely(execlists->csb_use_mmio)) {
+ intel_uncore_forcewake_get(i915, execlists->fw_domains);
+ fw = true;
- head = readl(i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)));
- tail = GEN8_CSB_WRITE_PTR(head);
- head = GEN8_CSB_READ_PTR(head);
- execlists->csb_head = head;
- } else {
- const int write_idx =
- intel_hws_csb_write_index(i915) -
- I915_HWS_CSB_BUF0_INDEX;
+ buf = (u32 * __force)
+ (i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_BUF_LO(engine, 0)));
- head = execlists->csb_head;
- tail = READ_ONCE(buf[write_idx]);
- rmb(); /* Hopefully paired with a wmb() in HW */
- }
- GEM_TRACE("%s cs-irq head=%d [%d%s], tail=%d [%d%s]\n",
- engine->name,
- head, GEN8_CSB_READ_PTR(readl(i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)))), fw ? "" : "?",
- tail, GEN8_CSB_WRITE_PTR(readl(i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)))), fw ? "" : "?");
+ head = readl(i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)));
+ tail = GEN8_CSB_WRITE_PTR(head);
+ head = GEN8_CSB_READ_PTR(head);
+ execlists->csb_head = head;
+ } else {
+ const int write_idx =
+ intel_hws_csb_write_index(i915) -
+ I915_HWS_CSB_BUF0_INDEX;
- while (head != tail) {
- struct i915_request *rq;
- unsigned int status;
- unsigned int count;
+ head = execlists->csb_head;
+ tail = READ_ONCE(buf[write_idx]);
+ rmb(); /* Hopefully paired with a wmb() in HW */
+ }
+ GEM_TRACE("%s cs-irq head=%d [%d%s], tail=%d [%d%s]\n",
+ engine->name,
+ head, GEN8_CSB_READ_PTR(readl(i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)))), fw ? "" : "?",
+ tail, GEN8_CSB_WRITE_PTR(readl(i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)))), fw ? "" : "?");
- if (++head == GEN8_CSB_ENTRIES)
- head = 0;
+ while (head != tail) {
+ struct i915_request *rq;
+ unsigned int status;
+ unsigned int count;
- /*
- * We are flying near dragons again.
- *
- * We hold a reference to the request in execlist_port[]
- * but no more than that. We are operating in softirq
- * context and so cannot hold any mutex or sleep. That
- * prevents us stopping the requests we are processing
- * in port[] from being retired simultaneously (the
- * breadcrumb will be complete before we see the
- * context-switch). As we only hold the reference to the
- * request, any pointer chasing underneath the request
- * is subject to a potential use-after-free. Thus we
- * store all of the bookkeeping within port[] as
- * required, and avoid using unguarded pointers beneath
- * request itself. The same applies to the atomic
- * status notifier.
- */
+ if (++head == GEN8_CSB_ENTRIES)
+ head = 0;
- status = READ_ONCE(buf[2 * head]); /* maybe mmio! */
- GEM_TRACE("%s csb[%d]: status=0x%08x:0x%08x, active=0x%x\n",
- engine->name, head,
- status, buf[2*head + 1],
- execlists->active);
-
- if (status & (GEN8_CTX_STATUS_IDLE_ACTIVE |
- GEN8_CTX_STATUS_PREEMPTED))
- execlists_set_active(execlists,
- EXECLISTS_ACTIVE_HWACK);
- if (status & GEN8_CTX_STATUS_ACTIVE_IDLE)
- execlists_clear_active(execlists,
- EXECLISTS_ACTIVE_HWACK);
-
- if (!(status & GEN8_CTX_STATUS_COMPLETED_MASK))
- continue;
+ /*
+ * We are flying near dragons again.
+ *
+ * We hold a reference to the request in execlist_port[]
+ * but no more than that. We are operating in softirq
+ * context and so cannot hold any mutex or sleep. That
+ * prevents us stopping the requests we are processing
+ * in port[] from being retired simultaneously (the
+ * breadcrumb will be complete before we see the
+ * context-switch). As we only hold the reference to the
+ * request, any pointer chasing underneath the request
+ * is subject to a potential use-after-free. Thus we
+ * store all of the bookkeeping within port[] as
+ * required, and avoid using unguarded pointers beneath
+ * request itself. The same applies to the atomic
+ * status notifier.
+ */
- /* We should never get a COMPLETED | IDLE_ACTIVE! */
- GEM_BUG_ON(status & GEN8_CTX_STATUS_IDLE_ACTIVE);
+ status = READ_ONCE(buf[2 * head]); /* maybe mmio! */
+ GEM_TRACE("%s csb[%d]: status=0x%08x:0x%08x, active=0x%x\n",
+ engine->name, head,
+ status, buf[2*head + 1],
+ execlists->active);
+
+ if (status & (GEN8_CTX_STATUS_IDLE_ACTIVE |
+ GEN8_CTX_STATUS_PREEMPTED))
+ execlists_set_active(execlists,
+ EXECLISTS_ACTIVE_HWACK);
+ if (status & GEN8_CTX_STATUS_ACTIVE_IDLE)
+ execlists_clear_active(execlists,
+ EXECLISTS_ACTIVE_HWACK);
+
+ if (!(status & GEN8_CTX_STATUS_COMPLETED_MASK))
+ continue;
- if (status & GEN8_CTX_STATUS_COMPLETE &&
- buf[2*head + 1] == execlists->preempt_complete_status) {
- GEM_TRACE("%s preempt-idle\n", engine->name);
- complete_preempt_context(execlists);
- continue;
- }
+ /* We should never get a COMPLETED | IDLE_ACTIVE! */
+ GEM_BUG_ON(status & GEN8_CTX_STATUS_IDLE_ACTIVE);
- if (status & GEN8_CTX_STATUS_PREEMPTED &&
- execlists_is_active(execlists,
- EXECLISTS_ACTIVE_PREEMPT))
- continue;
+ if (status & GEN8_CTX_STATUS_COMPLETE &&
+ buf[2*head + 1] == execlists->preempt_complete_status) {
+ GEM_TRACE("%s preempt-idle\n", engine->name);
+ complete_preempt_context(execlists);
+ continue;
+ }
- GEM_BUG_ON(!execlists_is_active(execlists,
- EXECLISTS_ACTIVE_USER));
+ if (status & GEN8_CTX_STATUS_PREEMPTED &&
+ execlists_is_active(execlists,
+ EXECLISTS_ACTIVE_PREEMPT))
+ continue;
- rq = port_unpack(port, &count);
- GEM_TRACE("%s out[0]: ctx=%d.%d, global=%d (fence %llx:%d) (current %d), prio=%d\n",
- engine->name,
- port->context_id, count,
- rq ? rq->global_seqno : 0,
- rq ? rq->fence.context : 0,
- rq ? rq->fence.seqno : 0,
- intel_engine_get_seqno(engine),
- rq ? rq_prio(rq) : 0);
+ 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);
+ rq = port_unpack(port, &count);
+ GEM_TRACE("%s out[0]: ctx=%d.%d, global=%d (fence %llx:%d) (current %d), prio=%d\n",
+ engine->name,
+ port->context_id, count,
+ rq ? rq->global_seqno : 0,
+ rq ? rq->fence.context : 0,
+ rq ? rq->fence.seqno : 0,
+ intel_engine_get_seqno(engine),
+ rq ? rq_prio(rq) : 0);
+
+ /* Check the context/desc id for this event matches */
+ GEM_DEBUG_BUG_ON(buf[2 * head + 1] != port->context_id);
+
+ GEM_BUG_ON(count == 0);
+ if (--count == 0) {
+ /*
+ * On the final event corresponding to the
+ * submission of this context, we expect either
+ * an element-switch event or a completion
+ * event (and on completion, the active-idle
+ * marker). No more preemptions, lite-restore
+ * or otherwise.
+ */
+ GEM_BUG_ON(status & GEN8_CTX_STATUS_PREEMPTED);
+ GEM_BUG_ON(port_isset(&port[1]) &&
+ !(status & GEN8_CTX_STATUS_ELEMENT_SWITCH));
+ GEM_BUG_ON(!port_isset(&port[1]) &&
+ !(status & GEN8_CTX_STATUS_ACTIVE_IDLE));
- GEM_BUG_ON(count == 0);
- if (--count == 0) {
- /*
- * On the final event corresponding to the
- * submission of this context, we expect either
- * an element-switch event or a completion
- * event (and on completion, the active-idle
- * marker). No more preemptions, lite-restore
- * or otherwise.
- */
- GEM_BUG_ON(status & GEN8_CTX_STATUS_PREEMPTED);
- GEM_BUG_ON(port_isset(&port[1]) &&
- !(status & GEN8_CTX_STATUS_ELEMENT_SWITCH));
- GEM_BUG_ON(!port_isset(&port[1]) &&
- !(status & GEN8_CTX_STATUS_ACTIVE_IDLE));
+ /*
+ * We rely on the hardware being strongly
+ * ordered, that the breadcrumb write is
+ * coherent (visible from the CPU) before the
+ * user interrupt and CSB is processed.
+ */
+ GEM_BUG_ON(!i915_request_completed(rq));
- /*
- * We rely on the hardware being strongly
- * ordered, that the breadcrumb write is
- * coherent (visible from the CPU) before the
- * user interrupt and CSB is processed.
- */
- GEM_BUG_ON(!i915_request_completed(rq));
-
- execlists_context_schedule_out(rq,
- INTEL_CONTEXT_SCHEDULE_OUT);
- i915_request_put(rq);
-
- GEM_TRACE("%s completed ctx=%d\n",
- engine->name, port->context_id);
-
- port = execlists_port_complete(execlists, port);
- if (port_isset(port))
- execlists_user_begin(execlists, port);
- else
- execlists_user_end(execlists);
- } else {
- port_set(port, port_pack(rq, count));
- }
- }
+ execlists_context_schedule_out(rq,
+ INTEL_CONTEXT_SCHEDULE_OUT);
+ i915_request_put(rq);
- if (head != execlists->csb_head) {
- execlists->csb_head = head;
- writel(_MASKED_FIELD(GEN8_CSB_READ_PTR_MASK, head << 8),
- i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)));
+ GEM_TRACE("%s completed ctx=%d\n",
+ engine->name, port->context_id);
+
+ port = execlists_port_complete(execlists, port);
+ if (port_isset(port))
+ execlists_user_begin(execlists, port);
+ else
+ execlists_user_end(execlists);
+ } else {
+ port_set(port, port_pack(rq, count));
}
- } while (test_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted));
+ }
+
+ if (head != execlists->csb_head) {
+ execlists->csb_head = head;
+ writel(_MASKED_FIELD(GEN8_CSB_READ_PTR_MASK, head << 8),
+ i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)));
+ }
if (unlikely(fw))
intel_uncore_forcewake_put(i915, execlists->fw_domains);
--
2.18.0
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