On 12/08/16 07:25, [email protected] wrote:
From: Akash Goel <[email protected]>

With the addition of new Host2GuC actions related to GuC logging, there
is a need of a lock to serialize them, as they can execute concurrently
with each other and also with other existing actions.

v2: Use mutex in place of spinlock to serialize, as sleep can happen
     while waiting for the action's response from GuC. (Tvrtko)

Signed-off-by: Akash Goel <[email protected]>
---
  drivers/gpu/drm/i915/i915_guc_submission.c | 3 +++
  drivers/gpu/drm/i915/intel_guc.h           | 3 +++
  2 files changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c 
b/drivers/gpu/drm/i915/i915_guc_submission.c
index 1a2d648..cb9672b 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -88,6 +88,7 @@ static int host2guc_action(struct intel_guc *guc, u32 *data, 
u32 len)
                return -EINVAL;

        intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
+       mutex_lock(&guc->action_lock);

I would probably take the mutex before grabbing forcewake as a general rule. Not that I think it matters in this case since we don't expect any contention on this one.


        dev_priv->guc.action_count += 1;
        dev_priv->guc.action_cmd = data[0];
@@ -126,6 +127,7 @@ static int host2guc_action(struct intel_guc *guc, u32 
*data, u32 len)
        }
        dev_priv->guc.action_status = status;

+       mutex_unlock(&guc->action_lock);
        intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);

        return ret;
@@ -1312,6 +1314,7 @@ int i915_guc_submission_init(struct drm_i915_private 
*dev_priv)
                return -ENOMEM;

        ida_init(&guc->ctx_ids);
+       mutex_init(&guc->action_lock);
        guc_create_log(guc);
        guc_create_ads(guc);

diff --git a/drivers/gpu/drm/i915/intel_guc.h b/drivers/gpu/drm/i915/intel_guc.h
index 96ef7dc..e4ec8d8 100644
--- a/drivers/gpu/drm/i915/intel_guc.h
+++ b/drivers/gpu/drm/i915/intel_guc.h
@@ -156,6 +156,9 @@ struct intel_guc {

        uint64_t submissions[I915_NUM_ENGINES];
        uint32_t last_seqno[I915_NUM_ENGINES];
+
+       /* To serialize the Host2GuC actions */
+       struct mutex action_lock;
  };

  /* intel_guc_loader.c */


With or without the mutex vs forcewake ordering change:

Reviewed-by: Tvrtko Ursulin <[email protected]>

Regards,

Tvrtko
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