Re: [Intel-gfx] [PATCH] drm/i915: fix plane/cursor handling when runtime suspended

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Aug 14, 2014 at 12:06:02PM -0300, Paulo Zanoni wrote:
> From: Paulo Zanoni <paulo.r.zanoni@intel.com>
> 
> If we're runtime suspended and try to use the plane interfaces, we
> will get a lot of WARNs saying we did the wrong thing.
> 
> We need to get runtime PM references to pin the objects, and to
> change the fences. The pin functions are the ideal places for
> this, but intel_crtc_cursor_set_obj() doesn't call them, so we also
> have to add get/put calls inside it. There is no problem if we runtime
> suspend right after these functions are finished, because the
> registers written are forwarded to system memory.
> 
> Note: for a complete fix of the cursor-dpms test case, we also need
> the patch named "drm/i915: Don't try to enable cursor from setplane
> when crtc is disabled".
> 
> v2: - Narrow the put/get calls on intel_crtc_cursor_set_obj() (Daniel)
> v3: - Make get/put also surround the fence and unpin calls (Daniel and
>       Ville).
>     - Merge all the plane changes into a single patch since they're
>       the same fix.
>     - Add the comment requested by Daniel.
> v4: - Remove spurious whitespace (Ville).
> v5: - Remove intel_crtc_update_cursor() chunk since Ville did an
>       equivalent fix in another patch (Ville).
> v6: - Remove unpin chunk: it will be on a separate patch (Ville,
>       Chris, Daniel).
> 
> Testcase: igt/pm_rpm/cursor
> Testcase: igt/pm_rpm/cursor-dpms
> Testcase: igt/pm_rpm/legacy-planes
> Testcase: igt/pm_rpm/legacy-planes-dpms
> Testcase: igt/pm_rpm/universal-planes
> Testcase: igt/pm_rpm/universal-planes-dpms
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=81645
> Cc: stable@vger.kernel.org
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> 
> I talked with Daniel and we agreed to leave any possible fixes related with the
> "unpin" functions to separate patches, possibly requiring separate IGT test
> cases.
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 3813526..17bc661 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2149,6 +2149,15 @@ intel_pin_and_fence_fb_obj(struct drm_device *dev,
>  	if (need_vtd_wa(dev) && alignment < 256 * 1024)
>  		alignment = 256 * 1024;
>  
> +	/*
> +	 * Global gtt pte registers are special registers which actually forward
> +	 * writes to a chunk of system memory. Which means that there is no risk
> +	 * that the register values disappear as soon as we call
> +	 * intel_runtime_pm_put(), so it is correct to wrap only the
> +	 * pin/unpin/fence and not more.
> +	 */
> +	intel_runtime_pm_get(dev_priv);
> +
>  	dev_priv->mm.interruptible = false;
>  	ret = i915_gem_object_pin_to_display_plane(obj, alignment, pipelined);
>  	if (ret)
> @@ -2166,12 +2175,14 @@ intel_pin_and_fence_fb_obj(struct drm_device *dev,
>  	i915_gem_object_pin_fence(obj);
>  
>  	dev_priv->mm.interruptible = true;
> +	intel_runtime_pm_put(dev_priv);
>  	return 0;
>  
>  err_unpin:
>  	i915_gem_object_unpin_from_display_plane(obj);
>  err_interruptible:
>  	dev_priv->mm.interruptible = true;
> +	intel_runtime_pm_put(dev_priv);
>  	return ret;
>  }
>  
> @@ -8201,6 +8212,7 @@ static int intel_crtc_cursor_set_obj(struct drm_crtc *crtc,
>  				     uint32_t width, uint32_t height)
>  {
>  	struct drm_device *dev = crtc->dev;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
>  	enum pipe pipe = intel_crtc->pipe;
>  	unsigned old_width, stride;
> @@ -8231,6 +8243,16 @@ static int intel_crtc_cursor_set_obj(struct drm_crtc *crtc,
>  
>  	/* we only need to pin inside GTT if cursor is non-phy */
>  	mutex_lock(&dev->struct_mutex);
> +
> +	/*
> +	 * Global gtt pte registers are special registers which actually forward
> +	 * writes to a chunk of system memory. Which means that there is no risk
> +	 * that the register values disappear as soon as we call
> +	 * intel_runtime_pm_put(), so it is correct to wrap only the
> +	 * pin/unpin/fence and not more.
> +	 */
> +	intel_runtime_pm_get(dev_priv);
> +

Only the !cursor_needs_physical case need runtime pm get/put. I thought
the calls were there originally, but I guess they got moved out. I
suppose it's not a huge deal either way, but the current approach does
give the reader the wrong impression that the unpin and frontbuffer
tracking would also need a rpm reference.

>  	if (!INTEL_INFO(dev)->cursor_needs_physical) {
>  		unsigned alignment;
>  
> @@ -8280,6 +8302,10 @@ static int intel_crtc_cursor_set_obj(struct drm_crtc *crtc,
>  
>  	i915_gem_track_fb(intel_crtc->cursor_bo, obj,
>  			  INTEL_FRONTBUFFER_CURSOR(pipe));
> +
> +	if (obj)
> +		intel_runtime_pm_put(dev_priv);
> +
>  	mutex_unlock(&dev->struct_mutex);
>  
>  	old_width = intel_crtc->cursor_width;
> @@ -8301,6 +8327,7 @@ static int intel_crtc_cursor_set_obj(struct drm_crtc *crtc,
>  fail_unpin:
>  	i915_gem_object_unpin_from_display_plane(obj);
>  fail_locked:
> +	intel_runtime_pm_put(dev_priv);
>  	mutex_unlock(&dev->struct_mutex);
>  fail:
>  	drm_gem_object_unreference_unlocked(&obj->base);
> -- 
> 2.0.1
> 
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-- 
Ville Syrjälä
Intel OTC