drm/i915: Convert engine->write_tail to operate on a request
If we rewrite the I915_WRITE_TAIL specialisation for the legacy
ringbuffer as submitting the request onto the ringbuffer, we can unify
the vfunc with both execlists and GuC in the next patch.
v2: Drop the modulus from the I915_WRITE_TAIL as it is currently being
applied in intel_ring_advance() after every command packet, and add a
comment explaining why we need the modulus at all.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469432687-22756-22-git-send-email-chris@chris-wilson.co.uk
Link: http://patchwork.freedesktop.org/patch/msgid/1470174640-18242-12-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 0c3c718..14d2ea3 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -204,8 +204,6 @@
int (*init_context)(struct drm_i915_gem_request *req);
- void (*write_tail)(struct intel_engine_cs *engine,
- u32 value);
int (*add_request)(struct drm_i915_gem_request *req);
/* Some chipsets are not quite as coherent as advertised and need
* an expensive kick to force a true read of the up-to-date seqno.
@@ -296,6 +294,7 @@
#define I915_DISPATCH_SECURE 0x1
#define I915_DISPATCH_PINNED 0x2
#define I915_DISPATCH_RS 0x4
+ void (*submit_request)(struct drm_i915_gem_request *req);
/**
* List of objects currently involved in rendering from the
@@ -461,6 +460,13 @@
static inline void intel_ring_advance(struct intel_ring *ring)
{
+ /* The modulus is required so that we avoid writing
+ * request->tail == ring->size, rather than the expected 0,
+ * into the RING_TAIL register as that can cause a GPU hang.
+ * As this is only strictly required for the request->tail,
+ * and only then as we write the value into hardware, we can
+ * one day remove the modulus after every command packet.
+ */
ring->tail &= ring->size - 1;
}