drm/i915: Make execlist port count variable

As we emulate execlists on top of the GuC workqueue, it is not
restricted to just 2 ports and we can increase that number arbitrarily
to trade-off queue depth (i.e. scheduling latency) against pipeline
bubbles.

v2: rebase. better commit msg (Chris)
v3: rebase

Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20170922124307.10914-5-mika.kuoppala@intel.com

1 files changed, 17 insertions, 4 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 0eae5936bc3c..56d7ae9f298b 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -234,7 +234,14 @@ struct intel_engine_execlists {
                  * @context_id: context ID for port
                  */
                 GEM_DEBUG_DECL(u32 context_id);
-        } port[2];
+
+#define EXECLIST_MAX_PORTS 2
+        } port[EXECLIST_MAX_PORTS];
+
+        /**
+         * @port_mask: number of execlist ports - 1
+         */
+        unsigned int port_mask;
 
         /**
          * @queue: queue of requests, in priority lists
@@ -511,16 +518,22 @@ struct intel_engine_cs {
         u32 (*get_cmd_length_mask)(u32 cmd_header);
 };
 
+static inline unsigned int
+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,
                         struct execlist_port * const port)
 {
-        struct execlist_port * const port1 = &execlists->port[1];
+        const unsigned int m = execlists->port_mask;
 
         GEM_BUG_ON(port_index(port, execlists) != 0);
 
-        *port = *port1;
-        memset(port1, 0, sizeof(struct execlist_port));
+        memmove(port, port + 1, m * sizeof(struct execlist_port));
+        memset(port + m, 0, sizeof(struct execlist_port));
 }
 
 static inline unsigned int