gpu: nvgpu: move gpfifo submit wait to userspace

Instead of blocking for gpfifo space in the nvgpu driver,
return -EAGAIN and allow userspace to decide the blocking
policy.

Bug 1795076

Change-Id: Ie091caa92aad3f68bc01a3456ad948e76883bc50
Signed-off-by: Aingara Paramakuru <aparamakuru@nvidia.com>
Reviewed-on: http://git-master/r/1202591
(cherry picked from commit 8056f422c6a34a4239fc4993c40c2e517c932714)
Reviewed-on: http://git-master/r/1203800
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 9 insertions, 23 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/channel_gk20a.c b/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
index 4c03f955..b4c132ce 100644
--- a/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
@@ -1194,7 +1194,6 @@ struct channel_gk20a *gk20a_open_new_channel(struct gk20a *g,
 
         init_waitqueue_head(&ch->notifier_wq);
         init_waitqueue_head(&ch->semaphore_wq);
-        init_waitqueue_head(&ch->submit_wq);
 
         ch->update_fn = NULL;
         ch->update_fn_data = NULL;
@@ -1974,9 +1973,6 @@ void gk20a_channel_update(struct channel_gk20a *c, int nr_completed)
                 return;
         }
 
-        update_gp_get(c->g, c);
-        wake_up(&c->submit_wq);
-
         trace_gk20a_channel_update(c->hw_chid);
         gk20a_channel_schedule_job_clean_up(c);
 
@@ -2181,22 +2177,16 @@ int gk20a_submit_channel_gpfifo(struct channel_gk20a *c,
         gk20a_dbg_info("pre-submit put %d, get %d, size %d",
                 c->gpfifo.put, c->gpfifo.get, c->gpfifo.entry_num);
 
-        /* Make sure we have enough space for gpfifo entries. If not,
-         * wait for signals from completed submits */
+        /*
+         * Make sure we have enough space for gpfifo entries. Check cached
+         * values first and then read from HW. If no space, return EAGAIN
+         * and let userpace decide to re-try request or not.
+         */
         if (gp_free_count(c) < num_entries + extra_entries) {
-                /* we can get here via locked ioctl and other paths too */
-                int locked_path = mutex_is_locked(&c->ioctl_lock);
-                if (locked_path)
-                        mutex_unlock(&c->ioctl_lock);
-
-                trace_gk20a_gpfifo_submit_wait_for_space(dev_name(c->g->dev));
-                err = wait_event_interruptible(c->submit_wq,
-                        get_gp_free_count(c) >= num_entries + extra_entries ||
-                        c->has_timedout);
-                trace_gk20a_gpfifo_submit_wait_for_space_done(dev_name(c->g->dev));
-
-                if (locked_path)
-                        mutex_lock(&c->ioctl_lock);
+                if (get_gp_free_count(c) < num_entries + extra_entries) {
+                        err = -EAGAIN;
+                        goto clean_up;
+                }
         }
 
         if (c->has_timedout) {
@@ -2204,10 +2194,6 @@ int gk20a_submit_channel_gpfifo(struct channel_gk20a *c,
                 goto clean_up;
         }
 
-        if (err) {
-                err = -ENOSPC;
-                goto clean_up;
-        }
 
         mutex_lock(&c->sync_lock);
         if (!c->sync) {