main/linux-lts: backport patch for i915 gpu

ref #11026
upstream bug: https://gitlab.freedesktop.org/drm/intel/issues/674

2 files changed, 140 insertions, 0 deletions

diff --git a/main/linux-lts/0001-drm-i915-gt-Detect-if-we-miss-WaIdleLiteRestore.patch b/main/linux-lts/0001-drm-i915-gt-Detect-if-we-miss-WaIdleLiteRestore.patch
new file mode 100644
index 0000000000..c95fc026a5
--- /dev/null
+++ b/main/linux-lts/0001-drm-i915-gt-Detect-if-we-miss-WaIdleLiteRestore.patch
@@ -0,0 +1,138 @@
+From 3d91696e92a354b7e23402ad9f38329f8853dde7 Mon Sep 17 00:00:00 2001
+From: Chris Wilson <chris@chris-wilson.co.uk>
+Date: Mon, 9 Dec 2019 02:32:15 +0000
+Subject: [PATCH] drm/i915/gt: Detect if we miss WaIdleLiteRestore
+
+In order to avoid confusing the HW, we must never submit an empty ring
+during lite-restore, that is we should always advance the RING_TAIL
+before submitting to stay ahead of the RING_HEAD.
+
+Normally this is prevented by keeping a couple of spare NOPs in the
+request->wa_tail so that on resubmission we can advance the tail. This
+relies on the request only being resubmitted once, which is the normal
+condition as it is seen once for ELSP[1] and then later in ELSP[0]. On
+preemption, the requests are unwound and the tail reset back to the
+normal end point (as we know the request is incomplete and therefore its
+RING_HEAD is even earlier).
+
+However, if this w/a should fail we would try and resubmit the request
+with the RING_TAIL already set to the location of this request's wa_tail
+potentially causing a GPU hang. We can spot when we do try and
+incorrectly resubmit without advancing the RING_TAIL and spare any
+embarrassment by forcing the context restore.
+
+In the case of preempt-to-busy, we leave the requests running on the HW
+while we unwind. As the ring is still live, we cannot rewind our
+rq->tail without forcing a reload so leave it set to rq->wa_tail and
+only force a reload if we resubmit after a lite-restore. (Normally, the
+forced reload will be a part of the preemption event.)
+
+Fixes: 22b7a426bbe1 ("drm/i915/execlists: Preempt-to-busy")
+Closes: https://gitlab.freedesktop.org/drm/intel/issues/673
+Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
+Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
+Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
+Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
+Cc: stable@kernel.vger.org
+Link: https://patchwork.freedesktop.org/patch/msgid/20191209023215.3519970-1-chris@chris-wilson.co.uk
+(cherry picked from commit 82c69bf58650e644c61aa2bf5100b63a1070fd2f)
+Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
+(cherry picked from commit f26a9e959a7b1588c59f7a919b41b67175b211d8)
+---
+ drivers/gpu/drm/i915/gt/intel_lrc.c | 44 +++++++++++++----------------
+ 1 file changed, 20 insertions(+), 24 deletions(-)
+
+diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
+index 4949b5ad860f..3ceaa4d70c5b 100644
+--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
++++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
+@@ -471,12 +471,6 @@ lrc_descriptor(struct intel_context *ce, struct intel_engine_cs *engine)
+ 	return desc;
+ }
+ 
+-static void unwind_wa_tail(struct i915_request *rq)
+-{
+-	rq->tail = intel_ring_wrap(rq->ring, rq->wa_tail - WA_TAIL_BYTES);
+-	assert_ring_tail_valid(rq->ring, rq->tail);
+-}
+-
+ static struct i915_request *
+ __unwind_incomplete_requests(struct intel_engine_cs *engine)
+ {
+@@ -490,12 +484,10 @@ __unwind_incomplete_requests(struct intel_engine_cs *engine)
+ 					 &engine->active.requests,
+ 					 sched.link) {
+ 		struct intel_engine_cs *owner;
+-
+ 		if (i915_request_completed(rq))
+ 			continue; /* XXX */
+ 
+ 		__i915_request_unsubmit(rq);
+-		unwind_wa_tail(rq);
+ 
+ 		/*
+ 		 * Push the request back into the queue for later resubmission.
+@@ -650,13 +642,29 @@ execlists_schedule_out(struct i915_request *rq)
+ 	i915_request_put(rq);
+ }
+ 
+-static u64 execlists_update_context(const struct i915_request *rq)
++static u64 execlists_update_context(struct i915_request *rq)
+ {
+ 	struct intel_context *ce = rq->hw_context;
+-	u64 desc;
++	u64 desc = ce->lrc_desc;
++	u32 tail;
+ 
+-	ce->lrc_reg_state[CTX_RING_TAIL + 1] =
+-		intel_ring_set_tail(rq->ring, rq->tail);
++	/*
++	 * WaIdleLiteRestore:bdw,skl
++	 *
++	 * We should never submit the context with the same RING_TAIL twice
++	 * just in case we submit an empty ring, which confuses the HW.
++	 *
++	 * We append a couple of NOOPs (gen8_emit_wa_tail) after the end of
++	 * the normal request to be able to always advance the RING_TAIL on
++	 * subsequent resubmissions (for lite restore). Should that fail us,
++	 * and we try and submit the same tail again, force the context
++	 * reload.
++	 */
++	tail = intel_ring_set_tail(rq->ring, rq->tail);
++	if (unlikely(ce->lrc_reg_state[CTX_RING_TAIL + 1] == tail))
++		desc |= CTX_DESC_FORCE_RESTORE;
++	ce->lrc_reg_state[CTX_RING_TAIL + 1] = tail;
++	rq->tail = rq->wa_tail;
+ 
+ 	/*
+ 	 * Make sure the context image is complete before we submit it to HW.
+@@ -675,9 +683,7 @@ static u64 execlists_update_context(const struct i915_request *rq)
+ 	 */
+ 	mb();
+ 
+-	desc = ce->lrc_desc;
+ 	ce->lrc_desc &= ~CTX_DESC_FORCE_RESTORE;
+-
+ 	return desc;
+ }
+ 
+@@ -1150,16 +1156,6 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
+ 			if (!list_is_last(&last->sched.link,
+ 					  &engine->active.requests))
+ 				return;
+-
+-			/*
+-			 * WaIdleLiteRestore:bdw,skl
+-			 * Apply the wa NOOPs to prevent
+-			 * ring:HEAD == rq:TAIL as we resubmit the
+-			 * request. See gen8_emit_fini_breadcrumb() for
+-			 * where we prepare the padding after the
+-			 * end of the request.
+-			 */
+-			last->tail = last->wa_tail;
+ 		}
+ 	}
+ 
+-- 
+2.25.0
+
diff --git a/main/linux-lts/APKBUILD b/main/linux-lts/APKBUILD
index 144b3d5598..a534a360fd 100644
--- a/main/linux-lts/APKBUILD
+++ b/main/linux-lts/APKBUILD
@@ -18,6 +18,7 @@ options="!strip"
 _config=${config:-config-lts.${CARCH}}
 install=
 source="https://cdn.kernel.org/pub/linux/kernel/v${pkgver%%.*}.x/linux-$_kernver.tar.xz
+	0001-drm-i915-gt-Detect-if-we-miss-WaIdleLiteRestore.patch
 	config-lts.aarch64
 	config-lts.armv7
 	config-lts.x86
@@ -220,6 +221,7 @@ _dev() {
 }
 
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