The patch below does not apply to the 3.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 5e4f518959bdf8a4f9c8f80879e4a0f7a95d2cb3 Mon Sep 17 00:00:00 2001 From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Date: Fri, 13 Feb 2015 14:35:59 +0000 Subject: [PATCH] drm/i915: Prevent TLB error on first execution on SNB Long ago I found that I was getting sporadic errors when booting SNB, with the symptom being that the first batch died with IPEHR != *ACTHD, typically caused by the TLB being invalid. These magically disappeared if I held the forcewake during the entire ring initialisation sequence. (It can probably be shortened to a short critical section, but the whole initialisation is full of register writes and so we would be taking and releasing forcewake almost continually, and so holding it over the entire sequence will probably be a net win!) Note some of the kernels I encounted the issue already had the deferred forcewake release, so it is still relevant. I know that there have been a few other reports with similar failure conditions on SNB, I think such as References: https://bugs.freedesktop.org/show_bug.cgi?id=80913 v2: Wrap i915_gem_init_hw() with its own security blanket as we take that path following resume and reset. Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index ac7fe39d38a3..5b205863b659 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -4793,6 +4793,9 @@ i915_gem_init_hw(struct drm_device *dev) if (INTEL_INFO(dev)->gen < 6 && !intel_enable_gtt()) return -EIO; + /* Double layer security blanket, see i915_gem_init() */ + intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL); + if (dev_priv->ellc_size) I915_WRITE(HSW_IDICR, I915_READ(HSW_IDICR) | IDIHASHMSK(0xf)); @@ -4825,7 +4828,7 @@ i915_gem_init_hw(struct drm_device *dev) for_each_ring(ring, dev_priv, i) { ret = ring->init_hw(ring); if (ret) - return ret; + goto out; } for (i = 0; i < NUM_L3_SLICES(dev); i++) @@ -4842,9 +4845,11 @@ i915_gem_init_hw(struct drm_device *dev) DRM_ERROR("Context enable failed %d\n", ret); i915_gem_cleanup_ringbuffer(dev); - return ret; + goto out; } +out: + intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL); return ret; } @@ -4878,6 +4883,14 @@ int i915_gem_init(struct drm_device *dev) dev_priv->gt.stop_ring = intel_logical_ring_stop; } + /* This is just a security blanket to placate dragons. + * On some systems, we very sporadically observe that the first TLBs + * used by the CS may be stale, despite us poking the TLB reset. If + * we hold the forcewake during initialisation these problems + * just magically go away. + */ + intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL); + ret = i915_gem_init_userptr(dev); if (ret) goto out_unlock; @@ -4904,6 +4917,7 @@ int i915_gem_init(struct drm_device *dev) } out_unlock: + intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL); mutex_unlock(&dev->struct_mutex); return ret; -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html