[Intel-gfx] [PATCH 2/2] drm/i915/guc: Use correct lock for CT event handler

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-11-20 09:56:36)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> CT event handler is called under the gt->irq_lock from the interrupt
> handling paths so make it the same from the init path. I don't think this
> mismatch caused any functional issue but we need to wean the code of the
> global i915->irq_lock.

ct_read definitely wants to be serialised. Is guc->irq_lock the right
choice?

> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/uc/intel_uc.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> index 220626c3ad81..6a0452815c41 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> @@ -203,7 +203,8 @@ static void guc_disable_interrupts(struct intel_guc *guc)
>  
>  static int guc_enable_communication(struct intel_guc *guc)
>  {
> -       struct drm_i915_private *i915 = guc_to_gt(guc)->i915;
> +       struct intel_gt *gt = guc_to_gt(guc);
> +       struct drm_i915_private *i915 = gt->i915;
>         int ret;
>  
>         GEM_BUG_ON(guc_communication_enabled(guc));
> @@ -223,9 +224,9 @@ static int guc_enable_communication(struct intel_guc *guc)
>         guc_enable_interrupts(guc);
>  
>         /* check for CT messages received before we enabled interrupts */
> -       spin_lock_irq(&i915->irq_lock);
> +       spin_lock_irq(&gt->irq_lock);
>         intel_guc_ct_event_handler(&guc->ct);
> -       spin_unlock_irq(&i915->irq_lock);
> +       spin_unlock_irq(&gt->irq_lock);

You used guc->irq_lock in the previous patch. I suggest
intel_guc_ct_event_handler() should specify what lock it requires.
-Chris