linux-kernel - [PATCH 4/5] drm/msm: Handle fence rollover

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Message-Id: <20211109181117.591148-5-robdclark@gmail.com>
Date:   Tue,  9 Nov 2021 10:11:04 -0800
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Jordan Crouse <jordan@...micpenguin.net>,
        Akhil P Oommen <akhilpo@...eaurora.org>,
        Rob Clark <robdclark@...omium.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 4/5] drm/msm: Handle fence rollover

From: Rob Clark <robdclark@...omium.org>

Add some helpers for fence comparision, which handle rollover properly,
and stop open coding fence seqno comparisions.

Signed-off-by: Rob Clark <robdclark@...omium.org>
---
 drivers/gpu/drm/msm/msm_fence.h | 12 ++++++++++++
 drivers/gpu/drm/msm/msm_gpu.c   |  6 +++---
 drivers/gpu/drm/msm/msm_gpu.h   |  2 +-
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_fence.h b/drivers/gpu/drm/msm/msm_fence.h
index 4783db528bcc..17ee3822b423 100644
--- a/drivers/gpu/drm/msm/msm_fence.h
+++ b/drivers/gpu/drm/msm/msm_fence.h
@@ -60,4 +60,16 @@ void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence);
 
 struct dma_fence * msm_fence_alloc(struct msm_fence_context *fctx);
 
+static inline bool
+fence_before(uint32_t a, uint32_t b)
+{
+   return (int32_t)(a - b) < 0;
+}
+
+static inline bool
+fence_after(uint32_t a, uint32_t b)
+{
+   return (int32_t)(a - b) > 0;
+}
+
 #endif
diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
index 13de1241d595..0f78c2615272 100644
--- a/drivers/gpu/drm/msm/msm_gpu.c
+++ b/drivers/gpu/drm/msm/msm_gpu.c
@@ -172,7 +172,7 @@ static void update_fences(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
 
 	spin_lock_irqsave(&ring->submit_lock, flags);
 	list_for_each_entry(submit, &ring->submits, node) {
-		if (submit->seqno > fence)
+		if (fence_after(submit->seqno, fence))
 			break;
 
 		msm_update_fence(submit->ring->fctx,
@@ -509,7 +509,7 @@ static void hangcheck_handler(struct timer_list *t)
 	if (fence != ring->hangcheck_fence) {
 		/* some progress has been made.. ya! */
 		ring->hangcheck_fence = fence;
-	} else if (fence < ring->seqno) {
+	} else if (fence_before(fence, ring->seqno)) {
 		/* no progress and not done.. hung! */
 		ring->hangcheck_fence = fence;
 		DRM_DEV_ERROR(dev->dev, "%s: hangcheck detected gpu lockup rb %d!\n",
@@ -523,7 +523,7 @@ static void hangcheck_handler(struct timer_list *t)
 	}
 
 	/* if still more pending work, reset the hangcheck timer: */
-	if (ring->seqno > ring->hangcheck_fence)
+	if (fence_after(ring->seqno, ring->hangcheck_fence))
 		hangcheck_timer_reset(gpu);
 
 	/* workaround for missing irq: */
diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index 0dcc31c27ac3..bd4e0024033e 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -258,7 +258,7 @@ static inline bool msm_gpu_active(struct msm_gpu *gpu)
 	for (i = 0; i < gpu->nr_rings; i++) {
 		struct msm_ringbuffer *ring = gpu->rb[i];
 
-		if (ring->seqno > ring->memptrs->fence)
+		if (fence_after(ring->seqno, ring->memptrs->fence))
 			return true;
 	}
 
-- 
2.31.1