linux-kernel - [PATCH] drm/amdkfd: Initialize only amdkfd's assigned pipelines

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Date:	Sat, 4 Apr 2015 13:10:11 +0300
From:	Oded Gabbay <oded.gabbay@....com>
To:	<linux-kernel@...r.kernel.org>
CC:	<stable@...r.kernel.org>
Subject: [PATCH] drm/amdkfd: Initialize only amdkfd's assigned pipelines

This is a backport of patch original made for kernel v4.0, with commit id
1365aa6266fad0669487240af3f098593796172c

This patch fixes a bug in the initialization of the pipelines. The
init_pipelines() function was called with a constant value of 0 in the
first_pipe argument. This is an error because amdkfd doesn't handle pipe 0.

The correct way is to pass the value that get_first_pipe() returns as the
argument for first_pipe.

This bug appeared in 3.19 (first version with amdkfd) and it causes around 15%
drop in CPU performance of Kaveri (A10-7850).

v2: Don't set get_first_pipe() as inline because it calls BUG_ON()

Signed-off-by: Oded Gabbay <oded.gabbay@....com>
Cc: stable@...r.kernel.org
Tested-by: Michel Dänzer <michel.daenzer@....com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
index 0fd5927..c80a8a3 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
@@ -56,9 +56,9 @@ static inline unsigned int get_pipes_num(struct device_queue_manager *dqm)
 	return dqm->dev->shared_resources.compute_pipe_count;
 }
 
-static inline unsigned int get_first_pipe(struct device_queue_manager *dqm)
+unsigned int get_first_pipe(struct device_queue_manager *dqm)
 {
-	BUG_ON(!dqm);
+	BUG_ON(!dqm || !dqm->dev);
 	return dqm->dev->shared_resources.first_compute_pipe;
 }
 
@@ -693,7 +693,7 @@ static int initialize_cpsch(struct device_queue_manager *dqm)
 	INIT_LIST_HEAD(&dqm->queues);
 	dqm->queue_count = dqm->processes_count = 0;
 	dqm->active_runlist = false;
-	retval = init_pipelines(dqm, get_pipes_num(dqm), 0);
+	retval = init_pipelines(dqm, get_pipes_num(dqm), get_first_pipe(dqm));
 	if (retval != 0)
 		goto fail_init_pipelines;
 
-- 
1.9.1

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