From: Mika Kuoppala <mika.kuopp...@intel.com>

Instead of trusting that first available port is at index 0,
use accessor to hide this. This is a preparation for a
following patches where head can be at arbitrary location
in the port array.

v2: improved commit message, elsp_ready readability (Chris)
v3: s/execlist_port_index/execlist_port (Chris)
v4: rebase to new naming
v5: fix port_next indexing
v6: adapt to preempt
v7: improved _port_next (Chris)
v8: whitespace, for loop (Chris),
    find_first_unset and GEM_BUG_ON after next_port in guc submission

Cc: Michał Winiarski <michal.winiar...@intel.com>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
Cc: Chris Wilson <ch...@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuopp...@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gpu_error.c       |  5 +-
 drivers/gpu/drm/i915/intel_engine_cs.c      | 18 +++++---
 drivers/gpu/drm/i915/intel_guc_submission.c | 71 ++++++++++++++++++++---------
 drivers/gpu/drm/i915/intel_lrc.c            | 55 +++++++++++++---------
 drivers/gpu/drm/i915/intel_ringbuffer.h     | 44 +++++++++++++++++-
 5 files changed, 139 insertions(+), 54 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c 
b/drivers/gpu/drm/i915/i915_gpu_error.c
index 876be8f1d930..02bae7d697da 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1350,11 +1350,12 @@ static void engine_record_requests(struct 
intel_engine_cs *engine,
 static void error_record_engine_execlists(struct intel_engine_cs *engine,
                                          struct drm_i915_error_engine *ee)
 {
-       const struct intel_engine_execlists * const execlists = 
&engine->execlists;
+       struct intel_engine_execlists * const execlists = &engine->execlists;
        unsigned int n;
 
        for (n = 0; n < execlists_num_ports(execlists); n++) {
-               struct drm_i915_gem_request *rq = 
port_request(&execlists->port[n]);
+               struct drm_i915_gem_request *rq =
+                       port_request(execlists_port(execlists, n));
 
                if (!rq)
                        break;
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c 
b/drivers/gpu/drm/i915/intel_engine_cs.c
index cffd0c812b7e..e954a50d20cf 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1667,7 +1667,7 @@ static void print_request(struct drm_printer *m,
 void intel_engine_dump(struct intel_engine_cs *engine, struct drm_printer *m)
 {
        struct intel_breadcrumbs * const b = &engine->breadcrumbs;
-       const struct intel_engine_execlists * const execlists = 
&engine->execlists;
+       struct intel_engine_execlists * const execlists = &engine->execlists;
        struct i915_gpu_error * const error = &engine->i915->gpu_error;
        struct drm_i915_private *dev_priv = engine->i915;
        struct drm_i915_gem_request *rq;
@@ -1780,16 +1780,20 @@ void intel_engine_dump(struct intel_engine_cs *engine, 
struct drm_printer *m)
 
                rcu_read_lock();
                for (idx = 0; idx < execlists_num_ports(execlists); idx++) {
-                       unsigned int count;
+                       struct execlist_port *port;
+                       unsigned int count, idx_abs;
+
+                       port = execlists_port(execlists, idx);
+                       idx_abs = port_index(port, execlists);
 
-                       rq = port_unpack(&execlists->port[idx], &count);
+                       rq = port_unpack(port, &count);
                        if (rq) {
-                               drm_printf(m, "\t\tELSP[%d] count=%d, ",
-                                          idx, count);
+                               drm_printf(m, "\t\tELSP[%d:%d] count=%d, ",
+                                          idx, idx_abs, count);
                                print_request(m, rq, "rq: ");
                        } else {
-                               drm_printf(m, "\t\tELSP[%d] idle\n",
-                                          idx);
+                               drm_printf(m, "\t\tELSP[%d:%d] idle\n",
+                                          idx, idx_abs);
                        }
                }
                drm_printf(m, "\t\tHW active? 0x%x\n", execlists->active);
diff --git a/drivers/gpu/drm/i915/intel_guc_submission.c 
b/drivers/gpu/drm/i915/intel_guc_submission.c
index 912ff143d531..615782744093 100644
--- a/drivers/gpu/drm/i915/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/intel_guc_submission.c
@@ -697,16 +697,18 @@ static void guc_submit(struct intel_engine_cs *engine)
 {
        struct intel_guc *guc = &engine->i915->guc;
        struct intel_engine_execlists * const execlists = &engine->execlists;
-       struct execlist_port *port = execlists->port;
        unsigned int n;
 
        for (n = 0; n < execlists_num_ports(execlists); n++) {
+               struct execlist_port *port;
                struct drm_i915_gem_request *rq;
                unsigned int count;
 
-               rq = port_unpack(&port[n], &count);
+               port = execlists_port(execlists, n);
+               rq = port_unpack(port, &count);
+
                if (rq && count == 0) {
-                       port_set(&port[n], port_pack(rq, ++count));
+                       port_set(port, port_pack(rq, ++count));
 
                        flush_ggtt_writes(rq->ring->vma);
 
@@ -715,6 +717,22 @@ static void guc_submit(struct intel_engine_cs *engine)
        }
 }
 
+static struct execlist_port *
+port_find_first_unset(struct intel_engine_execlists * const execlists,
+                     struct execlist_port * const prev)
+{
+       struct execlist_port *port = execlists_port_next(execlists, prev);
+
+       while (port != prev) {
+               if (!port_isset(port))
+                       return port;
+
+               port = execlists_port_next(execlists, port);
+       }
+
+       return NULL;
+}
+
 static void port_assign(struct execlist_port *port,
                        struct drm_i915_gem_request *rq)
 {
@@ -726,10 +744,8 @@ static void port_assign(struct execlist_port *port,
 static void guc_dequeue(struct intel_engine_cs *engine)
 {
        struct intel_engine_execlists * const execlists = &engine->execlists;
-       struct execlist_port *port = execlists->port;
+       struct execlist_port *port, *last_port;
        struct drm_i915_gem_request *last = NULL;
-       const struct execlist_port * const last_port =
-               &execlists->port[execlists->port_mask];
        bool submit = false;
        struct rb_node *rb;
 
@@ -740,6 +756,9 @@ static void guc_dequeue(struct intel_engine_cs *engine)
        if (!rb)
                goto unlock;
 
+       port = execlists_port_head(execlists);
+       last_port = execlists_port_tail(execlists);
+
        if (port_isset(port)) {
                if (HAS_LOGICAL_RING_PREEMPTION(engine->i915)) {
                        struct guc_preempt_work *preempt_work =
@@ -755,8 +774,8 @@ static void guc_dequeue(struct intel_engine_cs *engine)
                        }
                }
 
-               port++;
-               if (port_isset(port))
+               port = port_find_first_unset(execlists, port);
+               if (!port)
                        goto unlock;
        }
        GEM_BUG_ON(port_isset(port));
@@ -775,7 +794,9 @@ static void guc_dequeue(struct intel_engine_cs *engine)
 
                                if (submit)
                                        port_assign(port, last);
-                               port++;
+
+                               port = execlists_port_next(execlists, port);
+                               GEM_BUG_ON(port_isset(port));
                        }
 
                        INIT_LIST_HEAD(&rq->priotree.link);
@@ -804,29 +825,37 @@ static void guc_dequeue(struct intel_engine_cs *engine)
        spin_unlock_irq(&engine->timeline->lock);
 }
 
-static void guc_submission_tasklet(unsigned long data)
+static void guc_complete_ready_ports(struct intel_engine_execlists *execlists)
 {
-       struct intel_engine_cs * const engine = (struct intel_engine_cs *)data;
-       struct intel_engine_execlists * const execlists = &engine->execlists;
-       struct execlist_port *port = execlists->port;
-       struct drm_i915_gem_request *rq;
+       struct execlist_port *port = execlists_port_head(execlists);
+
+       while (port_isset(port)) {
+               struct drm_i915_gem_request *rq = port_request(port);
+
+               if (!i915_gem_request_completed(rq))
+                       break;
 
-       rq = port_request(&port[0]);
-       while (rq && i915_gem_request_completed(rq)) {
                trace_i915_gem_request_out(rq);
                i915_gem_request_put(rq);
 
-               execlists_port_complete(execlists, port);
+               port = execlists_head_complete(execlists, port);
+       };
 
-               rq = port_request(&port[0]);
-       }
-       if (!rq)
+       if (!port_isset(port))
                execlists_clear_active(execlists, EXECLISTS_ACTIVE_USER);
+}
+
+static void guc_submission_tasklet(unsigned long data)
+{
+       struct intel_engine_cs * const engine = (struct intel_engine_cs *)data;
+       struct intel_engine_execlists * const execlists = &engine->execlists;
+
+       guc_complete_ready_ports(execlists);
 
        if (execlists_is_active(execlists, EXECLISTS_ACTIVE_PREEMPT) &&
            intel_read_status_page(engine, I915_GEM_HWS_PREEMPT_INDEX) ==
            GUC_PREEMPT_FINISHED) {
-               execlists_cancel_port_requests(&engine->execlists);
+               execlists_cancel_port_requests(execlists);
                execlists_unwind_incomplete_requests(execlists);
 
                wait_for_guc_preempt_report(engine);
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 2a8160f603ab..bc839729a78c 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -430,24 +430,27 @@ static inline void elsp_write(u64 desc, u32 __iomem *elsp)
 
 static void execlists_submit_ports(struct intel_engine_cs *engine)
 {
-       struct execlist_port *port = engine->execlists.port;
+       struct intel_engine_execlists * const execlists = &engine->execlists;
        u32 __iomem *elsp =
                engine->i915->regs + i915_mmio_reg_offset(RING_ELSP(engine));
        unsigned int n;
 
-       for (n = execlists_num_ports(&engine->execlists); n--; ) {
+       for (n = execlists_num_ports(execlists); n--; ) {
+               struct execlist_port *port;
                struct drm_i915_gem_request *rq;
                unsigned int count;
                u64 desc;
 
-               rq = port_unpack(&port[n], &count);
+               port = execlists_port(execlists, n);
+               rq = port_unpack(port, &count);
                if (rq) {
                        GEM_BUG_ON(count > !n);
                        if (!count++)
                                execlists_context_schedule_in(rq);
-                       port_set(&port[n], port_pack(rq, count));
+
+                       port_set(port, port_pack(rq, count));
                        desc = execlists_update_context(rq);
-                       GEM_DEBUG_EXEC(port[n].context_id = 
upper_32_bits(desc));
+                       GEM_DEBUG_EXEC(port->context_id = upper_32_bits(desc));
 
                        GEM_TRACE("%s in[%d]:  ctx=%d.%d, seqno=%x\n",
                                  engine->name, n,
@@ -519,10 +522,8 @@ static void inject_preempt_context(struct intel_engine_cs 
*engine)
 static void execlists_dequeue(struct intel_engine_cs *engine)
 {
        struct intel_engine_execlists * const execlists = &engine->execlists;
-       struct execlist_port *port = execlists->port;
-       const struct execlist_port * const last_port =
-               &execlists->port[execlists->port_mask];
-       struct drm_i915_gem_request *last = port_request(port);
+       struct execlist_port *port, *last_port;
+       struct drm_i915_gem_request *last;
        struct rb_node *rb;
        bool submit = false;
 
@@ -553,6 +554,9 @@ static void execlists_dequeue(struct intel_engine_cs 
*engine)
        if (!rb)
                goto unlock;
 
+       port = execlists_port_head(execlists);
+       last = port_request(port);
+
        if (last) {
                /*
                 * Don't resubmit or switch until all outstanding
@@ -560,8 +564,8 @@ static void execlists_dequeue(struct intel_engine_cs 
*engine)
                 * know the next preemption status we see corresponds
                 * to this ELSP update.
                 */
-               GEM_BUG_ON(!port_count(&port[0]));
-               if (port_count(&port[0]) > 1)
+               GEM_BUG_ON(!port_count(port));
+               if (port_count(port) > 1)
                        goto unlock;
 
                /*
@@ -606,7 +610,7 @@ static void execlists_dequeue(struct intel_engine_cs 
*engine)
                         * the driver is unable to keep up the supply of new
                         * work).
                         */
-                       if (port_count(&port[1]))
+                       if (port_count(execlists_port_next(execlists, port)))
                                goto unlock;
 
                        /* WaIdleLiteRestore:bdw,skl
@@ -620,6 +624,8 @@ static void execlists_dequeue(struct intel_engine_cs 
*engine)
                }
        }
 
+       last_port = execlists_port_tail(execlists);
+
        do {
                struct i915_priolist *p = rb_entry(rb, typeof(*p), node);
                struct drm_i915_gem_request *rq, *rn;
@@ -666,8 +672,8 @@ static void execlists_dequeue(struct intel_engine_cs 
*engine)
 
                                if (submit)
                                        port_assign(port, last);
-                               port++;
 
+                               port = execlists_port_next(execlists, port);
                                GEM_BUG_ON(port_isset(port));
                        }
 
@@ -700,20 +706,21 @@ static void execlists_dequeue(struct intel_engine_cs 
*engine)
 void
 execlists_cancel_port_requests(struct intel_engine_execlists * const execlists)
 {
-       struct execlist_port *port = execlists->port;
        unsigned int num_ports = execlists_num_ports(execlists);
+       struct execlist_port *port;
 
-       while (num_ports-- && port_isset(port)) {
+       for (port = execlists_port_head(execlists);
+            num_ports-- && port_isset(port);
+            port = execlists_head_complete(execlists, port)) {
                struct drm_i915_gem_request *rq = port_request(port);
 
                GEM_BUG_ON(!execlists->active);
                intel_engine_context_out(rq->engine);
                execlists_context_status_change(rq, 
INTEL_CONTEXT_SCHEDULE_PREEMPTED);
                i915_gem_request_put(rq);
-
-               memset(port, 0, sizeof(*port));
-               port++;
        }
+
+       GEM_BUG_ON(port_isset(execlists_port_head(execlists)));
 }
 
 static void execlists_cancel_requests(struct intel_engine_cs *engine)
@@ -780,7 +787,6 @@ static void execlists_submission_tasklet(unsigned long data)
 {
        struct intel_engine_cs * const engine = (struct intel_engine_cs *)data;
        struct intel_engine_execlists * const execlists = &engine->execlists;
-       struct execlist_port * const port = execlists->port;
        struct drm_i915_private *dev_priv = engine->i915;
 
        /* We can skip acquiring intel_runtime_pm_get() here as it was taken
@@ -799,6 +805,8 @@ static void execlists_submission_tasklet(unsigned long data)
         * new request (outside of the context-switch interrupt).
         */
        while (test_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted)) {
+               struct execlist_port *port;
+
                /* The HWSP contains a (cacheable) mirror of the CSB */
                const u32 *buf =
                        &engine->status_page.page_addr[I915_HWS_CSB_BUF0_INDEX];
@@ -839,6 +847,8 @@ static void execlists_submission_tasklet(unsigned long data)
                          head, GEN8_CSB_READ_PTR(readl(dev_priv->regs + 
i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)))),
                          tail, GEN8_CSB_WRITE_PTR(readl(dev_priv->regs + 
i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)))));
 
+               port = execlists_port_head(execlists);
+
                while (head != tail) {
                        struct drm_i915_gem_request *rq;
                        unsigned int status;
@@ -914,14 +924,14 @@ static void execlists_submission_tasklet(unsigned long 
data)
                        GEM_BUG_ON(count == 0);
                        if (--count == 0) {
                                GEM_BUG_ON(status & GEN8_CTX_STATUS_PREEMPTED);
-                               GEM_BUG_ON(port_isset(&port[1]) &&
+                               GEM_BUG_ON(port_isset(execlists_port(execlists, 
1)) &&
                                           !(status & 
GEN8_CTX_STATUS_ELEMENT_SWITCH));
                                GEM_BUG_ON(!i915_gem_request_completed(rq));
                                execlists_context_schedule_out(rq);
                                trace_i915_gem_request_out(rq);
                                i915_gem_request_put(rq);
 
-                               execlists_port_complete(execlists, port);
+                               port = execlists_head_complete(execlists, port);
                        } else {
                                port_set(port, port_pack(rq, count));
                        }
@@ -961,6 +971,7 @@ static void insert_request(struct intel_engine_cs *engine,
 static void execlists_submit_request(struct drm_i915_gem_request *request)
 {
        struct intel_engine_cs *engine = request->engine;
+       struct intel_engine_execlists * const execlists = &engine->execlists;
        unsigned long flags;
 
        /* Will be called from irq-context when using foreign fences. */
@@ -968,7 +979,7 @@ static void execlists_submit_request(struct 
drm_i915_gem_request *request)
 
        insert_request(engine, &request->priotree, request->priotree.priority);
 
-       GEM_BUG_ON(!engine->execlists.first);
+       GEM_BUG_ON(!execlists->first);
        GEM_BUG_ON(list_empty(&request->priotree.link));
 
        spin_unlock_irqrestore(&engine->timeline->lock, flags);
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h 
b/drivers/gpu/drm/i915/intel_ringbuffer.h
index c68ab3ead83c..17f1fb4ded89 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -251,6 +251,11 @@ struct intel_engine_execlists {
        unsigned int port_mask;
 
        /**
+        * @port_head: first used execlist port
+        */
+       unsigned int port_head;
+
+       /**
         * @queue: queue of requests, in priority lists
         */
        struct rb_root queue;
@@ -643,8 +648,41 @@ execlists_num_ports(const struct intel_engine_execlists * 
const execlists)
        return execlists->port_mask + 1;
 }
 
-static inline void
-execlists_port_complete(struct intel_engine_execlists * const execlists,
+#define __port_add(start, n, mask) (((start) + (n)) & (mask))
+#define port_head_add(e, n) __port_add((e)->port_head, n, (e)->port_mask)
+
+/* Index starting from port_head */
+static inline struct execlist_port *
+execlists_port(struct intel_engine_execlists * const execlists,
+              const unsigned int n)
+{
+       return &execlists->port[port_head_add(execlists, n)];
+}
+
+static inline struct execlist_port *
+execlists_port_head(struct intel_engine_execlists * const execlists)
+{
+       return execlists_port(execlists, 0);
+}
+
+static inline struct execlist_port *
+execlists_port_tail(struct intel_engine_execlists * const execlists)
+{
+       return execlists_port(execlists, -1);
+}
+
+static inline struct execlist_port *
+execlists_port_next(struct intel_engine_execlists * const execlists,
+                   struct execlist_port *port)
+{
+       if (port++ == execlists->port + execlists->port_mask)
+               port = execlists->port;
+
+       return port;
+}
+
+static inline struct execlist_port *
+execlists_head_complete(struct intel_engine_execlists * const execlists,
                        struct execlist_port * const port)
 {
        const unsigned int m = execlists->port_mask;
@@ -654,6 +692,8 @@ execlists_port_complete(struct intel_engine_execlists * 
const execlists,
 
        memmove(port, port + 1, m * sizeof(struct execlist_port));
        memset(port + m, 0, sizeof(struct execlist_port));
+
+       return execlists_port_head(execlists);
 }
 
 static inline unsigned int
-- 
2.11.0

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