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, 5 insertions, 0 deletions

diff --git a/drivers/gpu/nvgpu/os/posix/clk_arb.c b/drivers/gpu/nvgpu/os/posix/clk_arb.c
index 63ab0f13..fcba0a26 100644
--- a/drivers/gpu/nvgpu/os/posix/clk_arb.c
+++ b/drivers/gpu/nvgpu/os/posix/clk_arb.c
@@ -52,6 +52,11 @@ int nvgpu_clk_arb_worker_init(struct gk20a *g)
         return -ENOSYS;
 }
 
+bool nvgpu_clk_arb_has_active_req(struct gk20a *g)
+{
+        return false;
+}
+
 int nvgpu_clk_arb_get_arbiter_actual_mhz(struct gk20a *g,
                                          u32 api_domain, u16 *actual_mhz)
 {