FAILED: patch "[PATCH] drm/amdgpu: restrict the sched jobs number to power of two" failed to apply to 4.4-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 5b0112356cf9a735632b26ff5f3450e1716c8598 Mon Sep 17 00:00:00 2001
From: Chunming Zhou <David1.Zhou@amd.com>
Date: Thu, 10 Dec 2015 17:34:33 +0800
Subject: [PATCH] drm/amdgpu: restrict the sched jobs number to power of two
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Chunming Zhou <David1.Zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
CC: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
index ee121ec2917b..17d1fb12128a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
@@ -252,7 +252,7 @@ uint64_t amdgpu_ctx_add_fence(struct amdgpu_ctx *ctx, struct amdgpu_ring *ring,
 	unsigned idx = 0;
 	struct fence *other = NULL;
 
-	idx = seq % amdgpu_sched_jobs;
+	idx = seq & (amdgpu_sched_jobs - 1);
 	other = cring->fences[idx];
 	if (other) {
 		signed long r;
@@ -292,7 +292,7 @@ struct fence *amdgpu_ctx_get_fence(struct amdgpu_ctx *ctx,
 		return NULL;
 	}
 
-	fence = fence_get(cring->fences[seq % amdgpu_sched_jobs]);
+	fence = fence_get(cring->fences[seq & (amdgpu_sched_jobs - 1)]);
 	spin_unlock(&ctx->ring_lock);
 
 	return fence;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 54af6ce7901f..587ff7145361 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -949,6 +949,15 @@ static bool amdgpu_check_pot_argument(int arg)
  */
 static void amdgpu_check_arguments(struct amdgpu_device *adev)
 {
+	if (amdgpu_sched_jobs < 4) {
+		dev_warn(adev->dev, "sched jobs (%d) must be at least 4\n",
+			 amdgpu_sched_jobs);
+		amdgpu_sched_jobs = 4;
+	} else if (!amdgpu_check_pot_argument(amdgpu_sched_jobs)){
+		dev_warn(adev->dev, "sched jobs (%d) must be a power of 2\n",
+			 amdgpu_sched_jobs);
+		amdgpu_sched_jobs = roundup_pow_of_two(amdgpu_sched_jobs);
+	}
 	/* vramlimit must be a power of two */
 	if (!amdgpu_check_pot_argument(amdgpu_vram_limit)) {
 		dev_warn(adev->dev, "vram limit (%d) must be a power of 2\n",