gpu: nvgpu: Fix crash on read fail of mc_boot_0_r

This CL handles
- erroneous use of boot_0 function pointer
before being assigned in __nvgpu_check_gpu_state
- And proper handling of error returned from gk20a_readl
in gk20a_mc_boot_0
With these fixes crash is not seen in case mc_boot_0 read
returns 0 in gk20a_mc_boot_0
- And also this handles the recursion caused by mc.boot_0()
calling nvgpu_readl and nvgpu_readl in turn
calling mc.boot_0 in case of read failure

Bug 2010966

Change-Id: Ia087811c67d88948b7fc5fff35e0fabc6ea91989
Signed-off-by: Supriya <ssharatkumar@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1616274
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

2 files changed, 13 insertions, 4 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/gk20a.c b/drivers/gpu/nvgpu/gk20a/gk20a.c
index c72b6193..0ccc8f6c 100644
--- a/drivers/gpu/nvgpu/gk20a/gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/gk20a.c
@@ -54,11 +54,17 @@
 
 void __nvgpu_check_gpu_state(struct gk20a *g)
 {
-        u32 boot_0 = g->ops.mc.boot_0(g, NULL, NULL, NULL);
+        u32 boot_0 = 0xffffffff;
 
+        if (!g->ops.mc.boot_0) {
+                nvgpu_err(g, "Can't determine GPU state, mc.boot_0 unset");
+                return;
+        }
+
+        boot_0 = g->ops.mc.boot_0(g, NULL, NULL, NULL);
         if (boot_0 == 0xffffffff) {
-                pr_err("nvgpu: GPU has disappeared from bus!!\n");
-                pr_err("nvgpu: Rebooting system!!\n");
+                nvgpu_err(g, "GPU has disappeared from bus!!");
+                nvgpu_err(g, "Rebooting system!!");
                 kernel_restart(NULL);
         }
 }
diff --git a/drivers/gpu/nvgpu/gk20a/mc_gk20a.c b/drivers/gpu/nvgpu/gk20a/mc_gk20a.c
index 9d9256bd..5027eaa4 100644
--- a/drivers/gpu/nvgpu/gk20a/mc_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/mc_gk20a.c
@@ -200,7 +200,10 @@ void gk20a_mc_reset(struct gk20a *g, u32 units)
 
 u32 gk20a_mc_boot_0(struct gk20a *g, u32 *arch, u32 *impl, u32 *rev)
 {
-        u32 val = gk20a_readl(g, mc_boot_0_r());
+        u32 val = __nvgpu_readl(g, mc_boot_0_r());
+
+        if (val == 0xffffffff)
+                return val;
 
         if (arch)
                 *arch = mc_boot_0_architecture_v(val) <<