drm/i915/lrc: Clear context restore/save inhibit flags for new contexts

CTX_CONTEXT_CONTROL (CTX_SR_CTL) operates as a masked register and so
will only apply the bits that are selected by the upper half. In the
case of selectively enabling sr inhibit, this may mean the context keeps
the current setting (so forgetting to save the context later, eventually
leading to a very upset GPU!).

Fixes: 517aaffe0c1b ("drm/i915/execlists: Inhibit context save/restore for the fake preempt context")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180125112443.12745-1-chris@chris-wilson.co.uk
Reviewed-by: Michel Thierry <michel.thierry@intel.com>

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 89e92defbcfe765f8db82929b9ef92372719ff94..29b14d7d4b07af31c6a7fcdb8ed227a2ebf6dbe7 100644 (file)
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -456,6 +456,12 @@ static void inject_preempt_context(struct intel_engine_cs *engine)
        ce->ring->tail &= (ce->ring->size - 1);
        ce->lrc_reg_state[CTX_RING_TAIL+1] = ce->ring->tail;
 
+       GEM_BUG_ON((ce->lrc_reg_state[CTX_CONTEXT_CONTROL + 1] &
+                   _MASKED_BIT_ENABLE(CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT |
+                                      CTX_CTRL_ENGINE_CTX_SAVE_INHIBIT)) !=
+                  _MASKED_BIT_ENABLE(CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT |
+                                     CTX_CTRL_ENGINE_CTX_SAVE_INHIBIT));
+
        GEM_TRACE("%s\n", engine->name);
        for (n = execlists_num_ports(&engine->execlists); --n; )
                elsp_write(0, engine->execlists.elsp);
@@ -2118,6 +2124,8 @@ static void execlists_init_reg_state(u32 *regs,
                                 MI_LRI_FORCE_POSTED;
 
        CTX_REG(regs, CTX_CONTEXT_CONTROL, RING_CONTEXT_CONTROL(engine),
+               _MASKED_BIT_DISABLE(CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT |
+                                   CTX_CTRL_ENGINE_CTX_SAVE_INHIBIT) |
                _MASKED_BIT_ENABLE(CTX_CTRL_INHIBIT_SYN_CTX_SWITCH |
                                   (HAS_RESOURCE_STREAMER(dev_priv) ?
                                   CTX_CTRL_RS_CTX_ENABLE : 0)));