No good reason why we must always use a static ringsize, so let
userspace select one during construction.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c | 139 +++++++++++++++++++-
 drivers/gpu/drm/i915/gt/intel_lrc.c         |   1 +
 include/uapi/drm/i915_drm.h                 |  19 +++
 3 files changed, 153 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c 
b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 0f1bbf5d1a11..a03bee30fac1 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -520,23 +520,30 @@ __create_context(struct drm_i915_private *i915)
        return ERR_PTR(err);
 }
 
-static void
+static int
 context_apply_all(struct i915_gem_context *ctx,
-                 void (*fn)(struct intel_context *ce, void *data),
+                 int (*fn)(struct intel_context *ce, void *data),
                  void *data)
 {
        struct i915_gem_engines_iter it;
        struct intel_context *ce;
+       int err = 0;
 
-       for_each_gem_engine(ce, i915_gem_context_lock_engines(ctx), it)
-               fn(ce, data);
+       for_each_gem_engine(ce, i915_gem_context_lock_engines(ctx), it) {
+               err = fn(ce, data);
+               if (err)
+                       break;
+       }
        i915_gem_context_unlock_engines(ctx);
+
+       return err;
 }
 
-static void __apply_ppgtt(struct intel_context *ce, void *vm)
+static int __apply_ppgtt(struct intel_context *ce, void *vm)
 {
        i915_vm_put(ce->vm);
        ce->vm = i915_vm_get(vm);
+       return 0;
 }
 
 static struct i915_address_space *
@@ -574,9 +581,10 @@ static void __set_timeline(struct intel_timeline **dst,
                intel_timeline_put(old);
 }
 
-static void __apply_timeline(struct intel_context *ce, void *timeline)
+static int __apply_timeline(struct intel_context *ce, void *timeline)
 {
        __set_timeline(&ce->timeline, timeline);
+       return 0;
 }
 
 static void __assign_timeline(struct i915_gem_context *ctx,
@@ -1151,6 +1159,104 @@ static int set_ppgtt(struct drm_i915_file_private 
*file_priv,
        return err;
 }
 
+static int __apply_ringsize(struct intel_context *ce, void *sz)
+{
+       int err;
+
+       err = i915_active_wait(&ce->active);
+       if (err < 0)
+               return err;
+
+       if (intel_context_lock_pinned(ce))
+               return -EINTR;
+
+       if (intel_context_is_pinned(ce)) {
+               err = -EBUSY; /* In active use, come back later! */
+               goto unlock;
+       }
+
+       if (test_bit(CONTEXT_ALLOC_BIT, &ce->flags)) {
+               struct intel_ring *ring;
+
+               /* Replace the existing ringbuffer */
+               ring = intel_engine_create_ring(ce->engine,
+                                               (unsigned long)sz);
+               if (IS_ERR(ring)) {
+                       err = PTR_ERR(ring);
+                       goto unlock;
+               }
+
+               intel_ring_put(ce->ring);
+               ce->ring = ring;
+
+               /* Context image will be updated on next pin */
+       } else {
+               ce->ring = sz;
+       }
+
+unlock:
+       intel_context_unlock_pinned(ce);
+       return err;
+}
+
+static int set_ringsize(struct i915_gem_context *ctx,
+                       struct drm_i915_gem_context_param *args)
+{
+       if (!HAS_LOGICAL_RING_CONTEXTS(ctx->i915))
+               return -ENODEV;
+
+       if (args->size)
+               return -EINVAL;
+
+       if (!IS_ALIGNED(args->value, I915_GTT_PAGE_SIZE))
+               return -EINVAL;
+
+       if (args->value < I915_GTT_PAGE_SIZE)
+               return -EINVAL;
+
+       if (args->value > 128 * I915_GTT_PAGE_SIZE)
+               return -EINVAL;
+
+       return context_apply_all(ctx,
+                                __apply_ringsize,
+                                __intel_context_ring_size(args->value));
+}
+
+static int __get_ringsize(struct intel_context *ce, void *arg)
+{
+       int num_pages;
+
+       if (intel_context_lock_pinned(ce))
+               return -EINTR;
+
+       if (test_bit(CONTEXT_ALLOC_BIT, &ce->flags))
+               num_pages = ce->ring->size / I915_GTT_PAGE_SIZE;
+       else
+               num_pages = (uintptr_t)ce->ring / I915_GTT_PAGE_SIZE;
+
+       intel_context_unlock_pinned(ce);
+       return num_pages; /* stop on first engine */
+}
+
+static int get_ringsize(struct i915_gem_context *ctx,
+                       struct drm_i915_gem_context_param *args)
+{
+       int num_pages;
+
+       if (!HAS_LOGICAL_RING_CONTEXTS(ctx->i915))
+               return -ENODEV;
+
+       if (args->size)
+               return -EINVAL;
+
+       num_pages = context_apply_all(ctx, __get_ringsize, NULL);
+       if (num_pages < 0)
+               return num_pages;
+
+       args->value = (u64)num_pages * I915_GTT_PAGE_SIZE;
+       return 0;
+}
+
 static int gen8_emit_rpcs_config(struct i915_request *rq,
                                 struct intel_context *ce,
                                 struct intel_sseu sseu)
@@ -1863,6 +1969,10 @@ static int ctx_setparam(struct drm_i915_file_private 
*fpriv,
                ret = set_persistence(ctx, args);
                break;
 
+       case I915_CONTEXT_PARAM_RINGSIZE:
+               ret = set_ringsize(ctx, args);
+               break;
+
        case I915_CONTEXT_PARAM_BAN_PERIOD:
        default:
                ret = -EINVAL;
@@ -1931,6 +2041,19 @@ static int clone_engines(struct i915_gem_context *dst,
                        __free_engines(clone, n);
                        goto err_unlock;
                }
+
+               /* Copy across the preferred ringsize */
+               clone->engines[n]->ring = e->engines[n]->ring;
+               if (test_bit(CONTEXT_ALLOC_BIT, &e->engines[n]->flags)) {
+                       if (intel_context_lock_pinned(e->engines[n])) {
+                               __free_engines(clone, n + 1);
+                               goto err_unlock;
+                       }
+
+                       clone->engines[n]->ring =
+                               
__intel_context_ring_size(e->engines[n]->ring->size);
+                       intel_context_unlock_pinned(e->engines[n]);
+               }
        }
        clone->num_engines = n;
 
@@ -2320,6 +2443,10 @@ int i915_gem_context_getparam_ioctl(struct drm_device 
*dev, void *data,
                args->value = i915_gem_context_is_persistent(ctx);
                break;
 
+       case I915_CONTEXT_PARAM_RINGSIZE:
+               ret = get_ringsize(ctx, args);
+               break;
+
        case I915_CONTEXT_PARAM_BAN_PERIOD:
        default:
                ret = -EINVAL;
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c 
b/drivers/gpu/drm/i915/gt/intel_lrc.c
index a7755d6dc48b..9d59debfd168 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -2309,6 +2309,7 @@ __execlists_update_reg_state(const struct intel_context 
*ce,
        GEM_BUG_ON(!intel_ring_offset_valid(ring, ring->tail));
 
        regs[CTX_RING_BUFFER_START] = i915_ggtt_offset(ring->vma);
+       regs[CTX_RING_BUFFER_CONTROL] = RING_CTL_SIZE(ring->size) | RING_VALID;
        regs[CTX_RING_HEAD] = ring->head;
        regs[CTX_RING_TAIL] = ring->tail;
 
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index b5fd5e4bd16e..cd35036a26a2 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -1587,6 +1587,25 @@ struct drm_i915_gem_context_param {
  * By default, new contexts allow persistence.
  */
 #define I915_CONTEXT_PARAM_PERSISTENCE 0xb
+
+/*
+ * I915_CONTEXT_PARAM_RINGSIZE:
+ *
+ * Sets the size of the CS ringbuffer to use for logical ring contexts. This
+ * applies a limit of how many batches can be queued to HW before the caller
+ * is blocked due to lack of space for more commands.
+ *
+ * Only reliably possible to be set prior to first use, i.e. during
+ * construction. At any later point, the current execution must be flushed as
+ * the ring can only be changed while the context is idle.
+ *
+ * Only applies to the current set of engine and lost when those engines
+ * are replaced by a new mapping (see I915_CONTEXT_PARAM_ENGINES).
+ *
+ * Must be between 4 - 512 KiB, in intervals of page size [4 KiB].
+ * Default is 16 KiB.
+ */
+#define I915_CONTEXT_PARAM_RINGSIZE    0xc
 /* Must be kept compact -- no holes and well documented */
 
        __u64 value;
-- 
2.24.0.rc0

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