[PATCH 06/10] drm/i915: Skip reset request if there is one already

Michel Thierry
2017-01-12T04:18:19Z

From: Mika Kuoppala <mika.kuoppala@linux.intel.com>

To perform engine reset we first disable engine to capture its state. This
is done by issuing a reset request. Because we are reusing existing
infrastructure, again when we actually reset an engine, reset function
checks engine mask and issues reset request again which is unnecessary. To
avoid this we check if the engine is already prepared, if so we just exit
from that point.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
---
drivers/gpu/drm/i915/intel_uncore.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index a28329bf0d05..dab9acf2bef3 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1761,10 +1761,15 @@ int intel_wait_for_register(struct drm_i915_private *dev_priv,
static int gen8_reset_engine_begin(struct intel_engine_cs *engine)
{
struct drm_i915_private *dev_priv = engine->i915;
+ const i915_reg_t reset_ctrl = RING_RESET_CTL(engine->mmio_base);
+ const u32 ready = RESET_CTL_REQUEST_RESET | RESET_CTL_READY_TO_RESET;
int ret;

- I915_WRITE_FW(RING_RESET_CTL(engine->mmio_base),
- _MASKED_BIT_ENABLE(RESET_CTL_REQUEST_RESET));
+ /* If engine has been already prepared, we can shortcut here */
+ if ((I915_READ_FW(reset_ctrl) & ready) == ready)
+ return 0;
+
+ I915_WRITE_FW(reset_ctrl, _MASKED_BIT_ENABLE(RESET_CTL_REQUEST_RESET));

ret = intel_wait_for_register_fw(dev_priv,
RING_RESET_CTL(engine->mmio_base),