gpu: nvgpu: gk20a: add busy lock

- add rw_semaphore busy_lock for gpu busy() path
- take read lock on busy_lock inside gk20a_busy()
  so that all usual requests can execute simultaneously
- write lock can be taken when we need to block all
  of the gk20a_busy() calls

Bug 1487804

Change-Id: I1b162b38bce9621723d3e45280c6076816cf771a
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/412060
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>

2 files changed, 9 insertions, 0 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/gk20a.c b/drivers/gpu/nvgpu/gk20a/gk20a.c
index 0c6b1e5f..a5b4fddc 100644
--- a/drivers/gpu/nvgpu/gk20a/gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/gk20a.c
@@ -1386,6 +1386,8 @@ static int gk20a_probe(struct platform_device *dev)
 
         gk20a_init_support(dev);
 
+        init_rwsem(&gk20a->busy_lock);
+
         spin_lock_init(&gk20a->mc_enable_lock);
 
         /* Initialize the platform interface. */
@@ -1544,6 +1546,9 @@ void gk20a_busy_noresume(struct platform_device *pdev)
 int gk20a_busy(struct platform_device *pdev)
 {
         int ret = 0;
+        struct gk20a *g = get_gk20a(pdev);
+
+        down_read(&g->busy_lock);
 
 #ifdef CONFIG_PM_RUNTIME
         ret = pm_runtime_get_sync(&pdev->dev);
@@ -1552,6 +1557,8 @@ int gk20a_busy(struct platform_device *pdev)
 #endif
         gk20a_scale_notify_busy(pdev);
 
+        up_read(&g->busy_lock);
+
         return ret < 0 ? ret : 0;
 }
 
diff --git a/drivers/gpu/nvgpu/gk20a/gk20a.h b/drivers/gpu/nvgpu/gk20a/gk20a.h
index ef7945f4..e6630ebf 100644
--- a/drivers/gpu/nvgpu/gk20a/gk20a.h
+++ b/drivers/gpu/nvgpu/gk20a/gk20a.h
@@ -220,6 +220,8 @@ struct gk20a {
 
         bool power_on;
 
+        struct rw_semaphore busy_lock;
+
         struct clk_gk20a clk;
         struct fifo_gk20a fifo;
         struct gr_gk20a gr;