From: Chris Wilson Date: Thu, 29 Mar 2018 23:45:18 +0100 Subject: drm/i915: Avoid sleeping inside per-engine reset MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Mika Kuoppala Cc: Michał Winiarski CC: Michel Thierry Cc: Jeff McGee Cc: Tvrtko Ursulin Reviewed-by: Michel Thierry Link: https://patchwork.freedesktop.org/patch/msgid/20180329224519.13598-1-chris@chris-wilson.co.uk Acked-by: Petr Tesarik --- 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();