drm/i915: Restore inhibiting the load of the default context

Following a GPU reset, we may leave the context in a poorly defined
state, and reloading from that context will leave the GPU flummoxed. For
secondary contexts, this will lead to that context being banned - but
currently it is also causing the default context to become banned,
leading to turmoil in the shared state.

This is a regression from

commit 6702cf16e0ba8b0129f5aa1b6609d4e9c70bc13b [v4.1]
Author: Ben Widawsky <benjamin.widawsky@intel.com>
Date:   Mon Mar 16 16:00:58 2015 +0000

    drm/i915: Initialize all contexts

which quietly introduced the removal of the MI_RESTORE_INHIBIT on the
default context.

v2: Mark the global default context as uninitialized on GPU reset so
that the context-local workarounds are reloaded upon re-enabling.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1448630935-27377-1-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: stable@vger.kernel.org
[danvet: This seems to fix a gpu hand on after the first resume,
resulting in any future suspend operation failing with -EIO because
the gpu seems to be in a funky state. Somehow this patch fixes that.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit 42f1cae8c079bcceb3cff079fddc3ff8852c788f)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 900ffd044db80049c47d0e976e59d406466de0c7..c25083c78ba7c21c7cdc92ed43f62c7e499851bb 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -347,6 +347,10 @@ void i915_gem_context_reset(struct drm_device *dev)
                        i915_gem_context_unreference(lctx);
                        ring->last_context = NULL;
                }
+
+               /* Force the GPU state to be reinitialised on enabling */
+               if (ring->default_context)
+                       ring->default_context->legacy_hw_ctx.initialized = false;
        }
 }
 
@@ -715,7 +719,7 @@ static int do_switch(struct drm_i915_gem_request *req)
        if (ret)
                goto unpin_out;
 
-       if (!to->legacy_hw_ctx.initialized) {
+       if (!to->legacy_hw_ctx.initialized || i915_gem_context_is_default(to)) {
                hw_flags |= MI_RESTORE_INHIBIT;
                /* NB: If we inhibit the restore, the context is not allowed to
                 * die because future work may end up depending on valid address