gpu: nvgpu: add check for is_railgated

When try to read '/sys/kernel/debug/gpu.0/railgate_residency'
debug fs node, NULL pointer access error can be happened if
is_railgated function is not assinged.
Add check for is_railgated before calling the function pointer.

Bug 200682233

Change-Id: I4a03d4e19b04d02815b792d7d967d4a1d5f42c35
Signed-off-by: Alvin Park <apark@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2459751
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: Hardik T Shah <hardikts@nvidia.com>
Reviewed-by: Phoenix Jung <pjung@nvidia.com>
Reviewed-by: Jay Kumar Bajaj <jbajaj@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
GVS: Gerrit_Virtual_Submit
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/gpu/nvgpu/os/linux/debug.c b/drivers/gpu/nvgpu/os/linux/debug.c
index 5f0703c8..d7e3f1e7 100644
--- a/drivers/gpu/nvgpu/os/linux/debug.c
+++ b/drivers/gpu/nvgpu/os/linux/debug.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2017-2018 NVIDIA Corporation.  All rights reserved.
+ * Copyright (C) 2017-2020 NVIDIA Corporation.  All rights reserved.
  *
  * This software is licensed under the terms of the GNU General Public
  * License version 2, as published by the Free Software Foundation, and
@@ -224,7 +224,7 @@ static int railgate_residency_show(struct seq_file *s, void *data)
         unsigned long total_rail_gate_time_ms;
         unsigned long total_rail_ungate_time_ms;
 
-        if (platform->is_railgated(dev_from_gk20a(g))) {
+        if (platform->is_railgated && platform->is_railgated(dev_from_gk20a(g))) {
                 time_since_last_state_transition_ms =
                                 jiffies_to_msecs(jiffies -
                                 g->pstats.last_rail_gate_complete);