drm/i915: Separate out reset flags from the reset counter

In preparation for introducing a per-engine reset, we can first separate
the mixing of the reset state from the global reset counter.

The loss of atomicity in updating the reset state poses a small problem
for handling the waiters. For requests, this is solved by advancing the
seqno so that a waiter waking up after the reset knows the request is
complete. For pending flips, we still rely on the increment of the
global reset epoch (as well as the reset-in-progress flag) to signify
when the hardware was reset.

The advantage, now that we do not inspect the reset state during reset
itself i.e. we no longer emit requests during reset, is that we can use
the atomic updates of the state flags to ensure that only one reset
worker is active.

v2: Mika spotted that I transformed the i915_gem_wait_for_error() wakeup
into a waiter wakeup.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Arun Siluvery <arun.siluvery@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470414607-32453-6-git-send-email-arun.siluvery@linux.intel.com
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160909131201.16673-7-chris@chris-wilson.co.uk

1 files changed, 7 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index ec613fd5e01c..24eb4b1b7540 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -233,16 +233,18 @@ void i915_gem_request_retire_upto(struct drm_i915_gem_request *req)
 	} while (tmp != req);
 }
 
-static int i915_gem_check_wedge(unsigned int reset_counter, bool interruptible)
+static int i915_gem_check_wedge(struct drm_i915_private *dev_priv)
 {
-	if (__i915_terminally_wedged(reset_counter))
+	struct i915_gpu_error *error = &dev_priv->gpu_error;
+
+	if (i915_terminally_wedged(error))
 		return -EIO;
 
-	if (__i915_reset_in_progress(reset_counter)) {
+	if (i915_reset_in_progress(error)) {
 		/* Non-interruptible callers can't handle -EAGAIN, hence return
 		 * -EIO unconditionally for these.
 		 */
-		if (!interruptible)
+		if (!dev_priv->mm.interruptible)
 			return -EIO;
 
 		return -EAGAIN;
@@ -331,7 +333,6 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
 		       struct i915_gem_context *ctx)
 {
 	struct drm_i915_private *dev_priv = engine->i915;
-	unsigned int reset_counter = i915_reset_counter(&dev_priv->gpu_error);
 	struct drm_i915_gem_request *req;
 	u32 seqno;
 	int ret;
@@ -340,7 +341,7 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
 	 * EIO if the GPU is already wedged, or EAGAIN to drop the struct_mutex
 	 * and restart.
 	 */
-	ret = i915_gem_check_wedge(reset_counter, dev_priv->mm.interruptible);
+	ret = i915_gem_check_wedge(dev_priv);
 	if (ret)
 		return ERR_PTR(ret);