[PATCH 3/3] drm/i915: Cleanup context switching through do_switch()

Chris Wilson
2012-07-15T11:35:16Z

When bug hunting, I found the interface to do_switch() overly
complicated and I believe festered the earlier bug. This aims to make
the code a little clearer.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ben Widawsky <ben@bwidawsk.net>
---
drivers/gpu/drm/i915/i915_gem_context.c | 57 ++++++++++++++-----------------
1 file changed, 26 insertions(+), 31 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 0cfc9d2..90a9c9e 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -97,8 +97,7 @@

static struct i915_hw_context *
i915_gem_context_get(struct drm_i915_file_private *file_priv, u32 id);
-static int do_switch(struct drm_i915_gem_object *from_obj,
- struct i915_hw_context *to, u32 seqno);
+static int do_switch(struct i915_hw_context *to);

static int get_context_size(struct drm_device *dev)
{
@@ -220,19 +219,20 @@ static int create_default_context(struct drm_i915_private *dev_priv)
*/
dev_priv->ring[RCS].default_context = ctx;
ret = i915_gem_object_pin(ctx->obj, CONTEXT_ALIGN, false);
- if (ret) {
- do_destroy(ctx);
- return ret;
- }
+ if (ret)
+ goto err_destroy;

- ret = do_switch(NULL, ctx, 0);
- if (ret) {
- i915_gem_object_unpin(ctx->obj);
- do_destroy(ctx);
- } else {
- DRM_DEBUG_DRIVER("Default HW context loaded\n");
- }
+ ret = do_switch(ctx);
+ if (ret)
+ goto err_unpin;

+ DRM_DEBUG_DRIVER("Default HW context loaded\n");
+ return 0;
+
+err_unpin:
+ i915_gem_object_unpin(ctx->obj);
+err_destroy:
+ do_destroy(ctx);
return ret;
}

@@ -359,17 +359,18 @@ mi_set_context(struct intel_ring_buffer *ring,
return ret;
}

-static int do_switch(struct drm_i915_gem_object *from_obj,
- struct i915_hw_context *to,
- u32 seqno)
+static int do_switch(struct i915_hw_context *to)
{
- struct intel_ring_buffer *ring = NULL;
+ struct intel_ring_buffer *ring = to->ring;
+ struct drm_i915_gem_object *from_obj = ring->last_context_obj;
u32 hw_flags = 0;
int ret;

- BUG_ON(to == NULL);
BUG_ON(from_obj != NULL && from_obj->pin_count == 0);

+ if (from_obj == to->obj)
+ return 0;
+
ret = i915_gem_object_pin(to->obj, CONTEXT_ALIGN, false);
if (ret)
return ret;
@@ -389,7 +390,6 @@ static int do_switch(struct drm_i915_gem_object *from_obj,
else if (WARN_ON_ONCE(from_obj == to->obj)) /* not yet expected */
hw_flags |= MI_FORCE_RESTORE;

- ring = to->ring;
ret = mi_set_context(ring, to, hw_flags);
if (ret) {
i915_gem_object_unpin(to->obj);
@@ -403,6 +403,7 @@ static int do_switch(struct drm_i915_gem_object *from_obj,
* MI_SET_CONTEXT instead of when the next seqno has completed.
*/
if (from_obj != NULL) {
+ u32 seqno = i915_gem_next_request_seqno(ring);
from_obj->base.read_domains = I915_GEM_DOMAIN_INSTRUCTION;
i915_gem_object_move_to_active(from_obj, ring, seqno);
/* As long as MI_SET_CONTEXT is serializing, ie. it flushes the
@@ -413,7 +414,7 @@ static int do_switch(struct drm_i915_gem_object *from_obj,
* swapped, but there is no way to do that yet.
*/
from_obj->dirty = 1;
- BUG_ON(from_obj->ring != to->ring);
+ BUG_ON(from_obj->ring != ring);
i915_gem_object_unpin(from_obj);

drm_gem_object_unreference(&from_obj->base);
@@ -444,10 +445,7 @@ int i915_switch_context(struct intel_ring_buffer *ring,
int to_id)
{
struct drm_i915_private *dev_priv = ring->dev->dev_private;
- struct drm_i915_file_private *file_priv = NULL;
struct i915_hw_context *to;
- struct drm_i915_gem_object *from_obj = ring->last_context_obj;
- int ret;

if (dev_priv->hw_contexts_disabled)
return 0;
@@ -455,21 +453,18 @@ int i915_switch_context(struct intel_ring_buffer *ring,
if (ring != &dev_priv->ring[RCS])
return 0;

- if (file)
- file_priv = file->driver_priv;
-
if (to_id == DEFAULT_CONTEXT_ID) {
to = ring->default_context;
} else {
- to = i915_gem_context_get(file_priv, to_id);
+ if (file == NULL)
+ return -EINVAL;
+
+ to = i915_gem_context_get(file->driver_priv, to_id);
if (to == NULL)
return -ENOENT;
}

- if (from_obj == to->obj)
- return 0;
-
- return do_switch(from_obj, to, i915_gem_next_request_seqno(to->ring));
+ return do_switch(to);
}

int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
--
1.7.10.4