drm/i915: preliminary context support

Very basic code for context setup/destruction in the driver.

Adds the file i915_gem_context.c This file implements HW context
support. On gen5+ a HW context consists of an opaque GPU object which is
referenced at times of context saves and restores.  With RC6 enabled,
the context is also referenced as the GPU enters and exists from RC6
(GPU has it's own internal power context, except on gen5).  Though
something like a context does exist for the media ring, the code only
supports contexts for the render ring.

In software, there is a distinction between contexts created by the
user, and the default HW context. The default HW context is used by GPU
clients that do not request setup of their own hardware context. The
default context's state is never restored to help prevent programming
errors. This would happen if a client ran and piggy-backed off another
clients GPU state.  The default context only exists to give the GPU some
offset to load as the current to invoke a save of the context we
actually care about. In fact, the code could likely be constructed,
albeit in a more complicated fashion, to never use the default context,
though that limits the driver's ability to swap out, and/or destroy
other contexts.

All other contexts are created as a request by the GPU client. These
contexts store GPU state, and thus allow GPU clients to not re-emit
state (and potentially query certain state) at any time. The kernel
driver makes certain that the appropriate commands are inserted.

There are 4 entry points into the contexts, init, fini, open, close.
The names are self-explanatory except that init can be called during
reset, and also during pm thaw/resume. As we expect our context to be
preserved across these events, we do not reinitialize in this case.

As Adam Jackson pointed out, The cutoff of 1MB where a HW context is
considered too big is arbitrary. The reason for this is even though
context sizes are increasing with every generation, they have yet to
eclipse even 32k. If we somehow read back way more than that, it
probably means BIOS has done something strange, or we're running on a
platform that wasn't designed for this.

v2: rename load/unload to init/fini (daniel)
remove ILK support for get_size() (indirectly daniel)
add HAS_HW_CONTEXTS macro to clarify supported platforms (daniel)
added comments (Ben)

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index ae4129b3cb3e..8d02951b988b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -821,6 +821,8 @@ typedef struct drm_i915_private {
         struct drm_property *force_audio_property;
 
         struct work_struct parity_error_work;
+        bool hw_contexts_disabled;
+        uint32_t hw_context_size;
 } drm_i915_private_t;
 
 /* Iterate over initialised rings */
@@ -1075,6 +1077,7 @@ struct drm_i915_file_private {
 #define HAS_LLC(dev)            (INTEL_INFO(dev)->has_llc)
 #define I915_NEED_GFX_HWS(dev)  (INTEL_INFO(dev)->need_gfx_hws)
 
+#define HAS_HW_CONTEXTS(dev)    (INTEL_INFO(dev)->gen >= 6)
 #define HAS_ALIASING_PPGTT(dev) (INTEL_INFO(dev)->gen >=6)
 
 #define HAS_OVERLAY(dev)                (INTEL_INFO(dev)->has_overlay)
@@ -1363,6 +1366,11 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 struct dma_buf *i915_gem_prime_export(struct drm_device *dev,
                                 struct drm_gem_object *gem_obj, int flags);
 
+/* i915_gem_context.c */
+void i915_gem_context_init(struct drm_device *dev);
+void i915_gem_context_fini(struct drm_device *dev);
+void i915_gem_context_open(struct drm_device *dev, struct drm_file *file);
+void i915_gem_context_close(struct drm_device *dev, struct drm_file *file);
 
 /* i915_gem_gtt.c */
 int __must_check i915_gem_init_aliasing_ppgtt(struct drm_device *dev);