gpu: nvgpu: note railgate_allowed in do_idle

The idling and unidling of deterministic channels in the
do_idle/do_unidle path assume that each deterministic channel holds a
power reference. This is no longer the case if railgating has been
allowed for a channel via the deterministic options ioctl which also
causes the channel to drop the power ref that it holds otherwise during
its lifetime.

All this is happening inside the deterministic_busy rwsem, which also
guards the ioctl changing those deterministic option states.

Bug 200327089

Change-Id: I9ce312bbaa459b3cf4a7541fa369186b78c3afdc
Signed-off-by: Konsta Holtta <kholtta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1642310
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: Alex Waterman <alexw@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/channel_gk20a.c b/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
index 64266fe5..371793ef 100644
--- a/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
@@ -2006,11 +2006,13 @@ void gk20a_channel_deterministic_idle(struct gk20a *g)
                 if (!gk20a_channel_get(ch))
                         continue;
 
-                if (ch->deterministic) {
+                if (ch->deterministic && !ch->deterministic_railgate_allowed) {
                         /*
                          * Drop the power ref taken when setting deterministic
                          * flag. deterministic_unidle will put this and the
-                         * channel ref back.
+                         * channel ref back. If railgate is allowed separately
+                         * for this channel, the power ref has already been put
+                         * away.
                          *
                          * Hold the channel ref: it must not get freed in
                          * between. A race could otherwise result in lost
@@ -2045,7 +2047,7 @@ void gk20a_channel_deterministic_unidle(struct gk20a *g)
                  * Deterministic state changes inside deterministic_busy lock,
                  * which we took in deterministic_idle.
                  */
-                if (ch->deterministic) {
+                if (ch->deterministic && !ch->deterministic_railgate_allowed) {
                         if (gk20a_busy(g))
                                 nvgpu_err(g, "cannot busy() again!");
                         /* Took this in idle() */