Revert "drm/i915/execlists: Reset RING registers upon resume"

This reverts commit f2a0409a08502d64fbe3990354dff5902b08d2fb which is
commit bafb2f7d4755bf1571bd5e9a03b97f3fc4fe69ae upstream.

It was reported to have problems.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Eric Blau <eblau1@gmail.com>
Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

1 files changed, 19 insertions, 31 deletions

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 4147e51cf893..67db1577ee49 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2152,42 +2152,30 @@ error_deref_obj:
 
 void intel_lr_context_resume(struct drm_i915_private *dev_priv)
 {
+        struct i915_gem_context *ctx = dev_priv->kernel_context;
         struct intel_engine_cs *engine;
-        struct i915_gem_context *ctx;
-
-        /* Because we emit WA_TAIL_DWORDS there may be a disparity
-         * between our bookkeeping in ce->ring->head and ce->ring->tail and
-         * that stored in context. As we only write new commands from
-         * ce->ring->tail onwards, everything before that is junk. If the GPU
-         * starts reading from its RING_HEAD from the context, it may try to
-         * execute that junk and die.
-         *
-         * So to avoid that we reset the context images upon resume. For
-         * simplicity, we just zero everything out.
-         */
-        list_for_each_entry(ctx, &dev_priv->context_list, link) {
-                for_each_engine(engine, dev_priv) {
-                        struct intel_context *ce = &ctx->engine[engine->id];
-                        u32 *reg;
 
-                        if (!ce->state)
-                                continue;
+        for_each_engine(engine, dev_priv) {
+                struct intel_context *ce = &ctx->engine[engine->id];
+                void *vaddr;
+                uint32_t *reg_state;
 
-                        reg = i915_gem_object_pin_map(ce->state->obj,
-                                                      I915_MAP_WB);
-                        if (WARN_ON(IS_ERR(reg)))
-                                continue;
+                if (!ce->state)
+                        continue;
 
-                        reg += LRC_STATE_PN * PAGE_SIZE / sizeof(*reg);
-                        reg[CTX_RING_HEAD+1] = 0;
-                        reg[CTX_RING_TAIL+1] = 0;
+                vaddr = i915_gem_object_pin_map(ce->state->obj, I915_MAP_WB);
+                if (WARN_ON(IS_ERR(vaddr)))
+                        continue;
 
-                        ce->state->obj->dirty = true;
-                        i915_gem_object_unpin_map(ce->state->obj);
+                reg_state = vaddr + LRC_STATE_PN * PAGE_SIZE;
 
-                        ce->ring->head = ce->ring->tail = 0;
-                        ce->ring->last_retired_head = -1;
-                        intel_ring_update_space(ce->ring);
-                }
+                reg_state[CTX_RING_HEAD+1] = 0;
+                reg_state[CTX_RING_TAIL+1] = 0;
+
+                ce->state->obj->dirty = true;
+                i915_gem_object_unpin_map(ce->state->obj);
+
+                ce->ring->head = 0;
+                ce->ring->tail = 0;
         }
 }