gpu: nvgpu: restrict devfreq during active clk_arb set requests

Restrict access to devfreq when there are active set requests in the
clk_arbiter. We make the following changes in the patch.

1) Add a global counter in the struct gk20a named clk_arb_global_nr which
is used to track the number of active set requests in the system.

2) Anytime a set request is successfully made by the userspace,
clk_arb_global_nr is incremented by 1 and during the completion of
request(releasing the corresponding file handle), clk_arb_global_nr is
decremented by 1.

3) gk20a_scale_target(invoked by devfreq to set the new frequency based
on load) atomically checks clk_arb_global_nr. If the value = 0, the
code simply continue or else if its > 0, it quits thus making devfreq
requests mutually exclusive with the clk_arbiter.

Bug 2061372

Change-Id: I5d19de03e45520f4ff8fccb97b1f1589d04c8ab8
Signed-off-by: Debarshi Dutta <ddutta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1790002
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/gpu/nvgpu/clk/clk_arb.c b/drivers/gpu/nvgpu/clk/clk_arb.c
index 452d9de3..3d97535d 100644
--- a/drivers/gpu/nvgpu/clk/clk_arb.c
+++ b/drivers/gpu/nvgpu/clk/clk_arb.c
@@ -772,6 +772,11 @@ int nvgpu_clk_arb_init_arbiter(struct gk20a *g)
         return err;
 }
 
+bool nvgpu_clk_arb_has_active_req(struct gk20a *g)
+{
+        return (nvgpu_atomic_read(&g->clk_arb_global_nr) > 0);
+}
+
 void nvgpu_clk_arb_send_thermal_alarm(struct gk20a *g)
 {
         nvgpu_clk_arb_schedule_alarm(g,
@@ -854,10 +859,12 @@ void nvgpu_clk_arb_free_fd(struct nvgpu_ref *refcount)
         struct nvgpu_clk_dev *dev = container_of(refcount,
                         struct nvgpu_clk_dev, refcount);
         struct nvgpu_clk_session *session = dev->session;
+        struct gk20a *g = session->g;
 
-        nvgpu_clk_notification_queue_free(session->g, &dev->queue);
+        nvgpu_clk_notification_queue_free(g, &dev->queue);
 
-        nvgpu_kfree(session->g, dev);
+        nvgpu_atomic_dec(&g->clk_arb_global_nr);
+        nvgpu_kfree(g, dev);
 }
 
 void nvgpu_clk_arb_free_session(struct nvgpu_ref *refcount)