From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 29 Mar 2018 23:45:18 +0100
Subject: drm/i915: Avoid sleeping inside per-engine reset
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Git-commit: 5807e1c21dbd56c87f0e86ae6fe49ec745660c0d
Patch-mainline: v4.18-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166
Only sleep and repeat when asked for a full device reset (ALL_ENGINES)
and avoid using sleeping waits when asked for a per-engine reset. The
goal is to be able to use a per-engine reset from hardirq/softirq/timer
context. A consequence is that our individual wait timeouts are a
thousand times shorter, on the order of a hundred microseconds rather
than hundreds of millisecond. This may make hitting the timeouts more
common, but hopefully the fallover to the full-device reset will be
sufficient to pick up the pieces.
Note, that the sleeps inside older gen (pre-gen8) have been left as they
are only used in full device reset mode.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
CC: Michel Thierry <michel.thierry@intel.com>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180329224519.13598-1-chris@chris-wilson.co.uk
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/gpu/drm/i915/intel_uncore.c | 51 ++++++++++++++++++++++++------------
1 file changed, 34 insertions(+), 17 deletions(-)
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1702,11 +1702,10 @@ static void gen3_stop_engine(struct inte
const i915_reg_t mode = RING_MI_MODE(base);
I915_WRITE_FW(mode, _MASKED_BIT_ENABLE(STOP_RING));
- if (intel_wait_for_register_fw(dev_priv,
- mode,
- MODE_IDLE,
- MODE_IDLE,
- 500))
+ if (__intel_wait_for_register_fw(dev_priv,
+ mode, MODE_IDLE, MODE_IDLE,
+ 500, 0,
+ NULL))
DRM_DEBUG_DRIVER("%s: timed out on STOP_RING\n",
engine->name);
@@ -1860,9 +1859,10 @@ static int gen6_hw_domain_reset(struct d
__raw_i915_write32(dev_priv, GEN6_GDRST, hw_domain_mask);
/* Wait for the device to ack the reset requests */
- err = intel_wait_for_register_fw(dev_priv,
- GEN6_GDRST, hw_domain_mask, 0,
- 500);
+ err = __intel_wait_for_register_fw(dev_priv,
+ GEN6_GDRST, hw_domain_mask, 0,
+ 500, 0,
+ NULL);
if (err)
DRM_DEBUG_DRIVER("Wait for 0x%08x engines reset failed\n",
hw_domain_mask);
@@ -2027,11 +2027,12 @@ static int gen8_reset_engine_start(struc
I915_WRITE_FW(RING_RESET_CTL(engine->mmio_base),
_MASKED_BIT_ENABLE(RESET_CTL_REQUEST_RESET));
- ret = intel_wait_for_register_fw(dev_priv,
- RING_RESET_CTL(engine->mmio_base),
- RESET_CTL_READY_TO_RESET,
- RESET_CTL_READY_TO_RESET,
- 700);
+ ret = __intel_wait_for_register_fw(dev_priv,
+ RING_RESET_CTL(engine->mmio_base),
+ RESET_CTL_READY_TO_RESET,
+ RESET_CTL_READY_TO_RESET,
+ 700, 0,
+ NULL);
if (ret)
DRM_ERROR("%s: reset request timeout\n", engine->name);
@@ -2094,15 +2095,31 @@ int intel_gpu_reset(struct drm_i915_priv
int retry;
int ret;
- might_sleep();
+ /*
+ * We want to perform per-engine reset from atomic context (e.g.
+ * softirq), which imposes the constraint that we cannot sleep.
+ * However, experience suggests that spending a bit of time waiting
+ * for a reset helps in various cases, so for a full-device reset
+ * we apply the opposite rule and wait if we want to. As we should
+ * always follow up a failed per-engine reset with a full device reset,
+ * being a little faster, stricter and more error prone for the
+ * atomic case seems an acceptable compromise.
+ *
+ * Unfortunately this leads to a bimodal routine, when the goal was
+ * to have a single reset function that worked for resetting any
+ * number of engines simultaneously.
+ */
+ might_sleep_if(engine_mask == ALL_ENGINES);
- /* If the power well sleeps during the reset, the reset
+ /*
+ * If the power well sleeps during the reset, the reset
* request may be dropped and never completes (causing -EIO).
*/
intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
for (retry = 0; retry < 3; retry++) {
- /* We stop engines, otherwise we might get failed reset and a
+ /*
+ * We stop engines, otherwise we might get failed reset and a
* dead gpu (on elk). Also as modern gpu as kbl can suffer
* from system hang if batchbuffer is progressing when
* the reset is issued, regardless of READY_TO_RESET ack.
@@ -2120,7 +2137,7 @@ int intel_gpu_reset(struct drm_i915_priv
GEM_TRACE("engine_mask=%x\n", engine_mask);
ret = reset(dev_priv, engine_mask);
}
- if (ret != -ETIMEDOUT)
+ if (ret != -ETIMEDOUT || engine_mask != ALL_ENGINES)
break;
cond_resched();