diff options
| -rw-r--r-- | drivers/gpu/drm/i915/intel_lrc.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index c5b76082d695..721432ddf403 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -1618,7 +1618,23 @@ static int gen8_emit_bb_start(struct drm_i915_gem_request *req, if (IS_ERR(cs)) return PTR_ERR(cs); - /* WaDisableCtxRestoreArbitration:bdw,chv */ + /* + * WaDisableCtxRestoreArbitration:bdw,chv + * + * We don't need to perform MI_ARB_ENABLE as often as we do (in + * particular all the gen that do not need the w/a at all!), if we + * took care to make sure that on every switch into this context + * (both ordinary and for preemption) that arbitrartion was enabled + * we would be fine. However, there doesn't seem to be a downside to + * being paranoid and making sure it is set before each batch and + * every context-switch. + * + * Note that if we fail to enable arbitration before the request + * is complete, then we do not see the context-switch interrupt and + * the engine hangs (with RING_HEAD == RING_TAIL). + * + * That satisfies both the GPGPU w/a and our heavy-handed paranoia. + */ *cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE; /* FIXME(BDW): Address space and security selectors. */ |