On Mon, Oct 20, 2014 at 11:31:36AM +0100, Nick Hoath wrote:
> The execlist code was holding a pm reference for the lifetime of an
> execlist queue item. Having this pm reference is required when getting
> force wakes during execlists_elsp_write. As this happens inside an interrupt
> handler and retrieving the reference can sleep, it can't be done more fine
> grained. However, the matching execbuffer already holds a pm reference which
> covers this timeframe.
That's not entirely accurate. We keep the gpu out of runtime pm as long as
it's busy, which is done by the intel_mark_busy/idle functions. The
requests themselves don't actually hold a runtime pm reference.
Can you please update commit message and comments?
Also, I don't think this works without also reworking the way we retire
execlist items since atm they're retired in a complete separate work item.
So you can't actually rely on the overal gpu business runtime pm.
I think we need to assemeble all the different pieces of the
request/execlist puzzle into one patch series. Looking at each individual
piece doesn't make a lot of sense to me.
Thanks, Daniel
>
> Issue: VIZ-4274
> Signed-off-by: Nick Hoath <nicholas.hoath@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_lrc.c | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 1be836a..dc096de 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -297,7 +297,7 @@ static void execlists_elsp_write(struct intel_engine_cs *ring,
> *
> * The other problem is that we can't just call gen6_gt_force_wake_get()
> * because that function calls intel_runtime_pm_get(), which might sleep.
> - * Instead, we do the runtime_pm_get/put when creating/destroying requests.
> + * Instead, we rely on the requests pm get/put.
> */
> spin_lock_irqsave(&dev_priv->uncore.lock, flags);
> if (IS_CHERRYVIEW(dev_priv->dev)) {
> @@ -519,8 +519,6 @@ static void execlists_free_request_task(struct work_struct *work)
> struct drm_device *dev = req->ring->dev;
> struct drm_i915_private *dev_priv = dev->dev_private;
>
> - intel_runtime_pm_put(dev_priv);
> -
> mutex_lock(&dev->struct_mutex);
> i915_gem_context_unreference(req->ctx);
> mutex_unlock(&dev->struct_mutex);
> @@ -546,8 +544,6 @@ static int execlists_context_queue(struct intel_engine_cs *ring,
> req->tail = tail;
> INIT_WORK(&req->work, execlists_free_request_task);
>
> - intel_runtime_pm_get(dev_priv);
> -
> spin_lock_irqsave(&ring->execlist_lock, flags);
>
> list_for_each_entry(cursor, &ring->execlist_queue, execlist_link)
> --
> 2.1.1
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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