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>

9 files changed, 33 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)
diff --git a/drivers/gpu/nvgpu/gp10b/clk_arb_gp10b.c b/drivers/gpu/nvgpu/gp10b/clk_arb_gp10b.c
index 4dcc3ca5..78fb1261 100644
--- a/drivers/gpu/nvgpu/gp10b/clk_arb_gp10b.c
+++ b/drivers/gpu/nvgpu/gp10b/clk_arb_gp10b.c
@@ -215,6 +215,9 @@ int gp10b_init_clk_arbiter(struct gk20a *g)
                 goto init_fail;
         }
 
+        /* This is set for the duration of the default req */
+        nvgpu_atomic_inc(&g->clk_arb_global_nr);
+
         nvgpu_clk_arb_worker_enqueue(g, &arb->update_arb_work_item);
 
         do {
@@ -224,6 +227,8 @@ int gp10b_init_clk_arbiter(struct gk20a *g)
                         nvgpu_atomic_read(&arb->req_nr) != 0, 0);
         } while (nvgpu_atomic_read(&arb->req_nr) == 0);
 
+        /* Once the default request is completed, reduce the usage count */
+        nvgpu_atomic_dec(&g->clk_arb_global_nr);
 
         return arb->status;
 
diff --git a/drivers/gpu/nvgpu/include/nvgpu/clk_arb.h b/drivers/gpu/nvgpu/include/nvgpu/clk_arb.h
index 81b1df1b..a04e3542 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/clk_arb.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/clk_arb.h
@@ -295,6 +295,8 @@ int nvgpu_clk_arb_worker_init(struct gk20a *g);
 
 int nvgpu_clk_arb_init_arbiter(struct gk20a *g);
 
+bool nvgpu_clk_arb_has_active_req(struct gk20a *g);
+
 int nvgpu_clk_arb_get_arbiter_clk_range(struct gk20a *g, u32 api_domain,
                 u16 *min_mhz, u16 *max_mhz);
 
diff --git a/drivers/gpu/nvgpu/include/nvgpu/gk20a.h b/drivers/gpu/nvgpu/include/nvgpu/gk20a.h
index b8ca5754..5f875707 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/gk20a.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/gk20a.h
@@ -1596,6 +1596,8 @@ struct gk20a {
 
         struct nvgpu_mutex clk_arb_enable_lock;
 
+        nvgpu_atomic_t clk_arb_global_nr;
+
         struct gk20a_ce_app ce_app;
 
         bool ltc_intr_en_illegal_compstat;
diff --git a/drivers/gpu/nvgpu/os/linux/debug_clk_gm20b.c b/drivers/gpu/nvgpu/os/linux/debug_clk_gm20b.c
index 52eea83f..b8b95fd7 100644
--- a/drivers/gpu/nvgpu/os/linux/debug_clk_gm20b.c
+++ b/drivers/gpu/nvgpu/os/linux/debug_clk_gm20b.c
@@ -17,6 +17,7 @@
 #include <linux/seq_file.h>
 
 #include <nvgpu/io.h>
+#include <nvgpu/clk_arb.h>
 
 #include "gm20b/clk_gm20b.h"
 #include "os_linux.h"
@@ -33,6 +34,8 @@ static int rate_get(void *data, u64 *val)
 static int rate_set(void *data, u64 val)
 {
         struct gk20a *g = (struct gk20a *)data;
+        if (nvgpu_clk_arb_has_active_req(g))
+                return 0;
         return g->ops.clk.set_rate(g, CTRL_CLK_DOMAIN_GPCCLK, (u32)val);
 }
 DEFINE_SIMPLE_ATTRIBUTE(rate_fops, rate_get, rate_set, "%llu\n");
diff --git a/drivers/gpu/nvgpu/os/linux/driver_common.c b/drivers/gpu/nvgpu/os/linux/driver_common.c
index ebd0b40b..0a25cd3f 100644
--- a/drivers/gpu/nvgpu/os/linux/driver_common.c
+++ b/drivers/gpu/nvgpu/os/linux/driver_common.c
@@ -66,6 +66,9 @@ static void nvgpu_init_vars(struct gk20a *g)
         nvgpu_mutex_init(&g->tpc_pg_lock);
         nvgpu_mutex_init(&g->clk_arb_enable_lock);
 
+        /* Init the clock req count to 0 */
+        nvgpu_atomic_set(&g->clk_arb_global_nr, 0);
+
         l->regs_saved = l->regs;
         l->bar1_saved = l->bar1;
 
diff --git a/drivers/gpu/nvgpu/os/linux/ioctl_clk_arb.c b/drivers/gpu/nvgpu/os/linux/ioctl_clk_arb.c
index 2d9946b1..ff1cc00a 100644
--- a/drivers/gpu/nvgpu/os/linux/ioctl_clk_arb.c
+++ b/drivers/gpu/nvgpu/os/linux/ioctl_clk_arb.c
@@ -436,6 +436,7 @@ int nvgpu_clk_arb_commit_request_fd(struct gk20a *g,
         clk_arb_dbg(g, "requested target = %u\n",
                 (u32)dev->gpc2clk_target_mhz);
 
+        nvgpu_atomic_inc(&g->clk_arb_global_nr);
         nvgpu_ref_get(&dev->refcount);
         nvgpu_spinlock_acquire(&session->session_lock);
         nvgpu_list_add(&dev->node, &session->targets);
diff --git a/drivers/gpu/nvgpu/os/linux/scale.c b/drivers/gpu/nvgpu/os/linux/scale.c
index ecc8207a..cbb9fdc5 100644
--- a/drivers/gpu/nvgpu/os/linux/scale.c
+++ b/drivers/gpu/nvgpu/os/linux/scale.c
@@ -25,6 +25,7 @@
 
 #include <nvgpu/kmem.h>
 #include <nvgpu/log.h>
+#include <nvgpu/clk_arb.h>
 
 #include "gk20a/gk20a.h"
 #include "platform_gk20a.h"
@@ -154,6 +155,8 @@ static int gk20a_scale_target(struct device *dev, unsigned long *freq,
         unsigned long rounded_rate;
         unsigned long min_freq = 0, max_freq = 0;
 
+        if (nvgpu_clk_arb_has_active_req(g))
+                return 0;
         /*
          * Calculate floor and cap frequency values
          *
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)
 {