gpu: nvgpu: prevent hang on failing arbiter init

The current code can lead to application hang when
opening device on first time if the arbiter fails
to set the clocks

Also it solves a buffer overrun condition in case
the requested frequency is above the maximum range
of the VF curve

bug 1835042

Change-Id: I385401ea27d5cc4bfa41b7ca2eb3a1db53138418
Signed-off-by: David Nieto <dmartineznie@nvidia.com>
Reviewed-on: http://git-master/r/1245911
Reviewed-by: Thomas Fleury <tfleury@nvidia.com>
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-on: http://git-master/r/1268061
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit

1 files changed, 29 insertions, 17 deletions

diff --git a/drivers/gpu/nvgpu/clk/clk_arb.c b/drivers/gpu/nvgpu/clk/clk_arb.c
index 1b974d17..f3d6cfab 100644
--- a/drivers/gpu/nvgpu/clk/clk_arb.c
+++ b/drivers/gpu/nvgpu/clk/clk_arb.c
@@ -83,6 +83,7 @@ struct nvgpu_clk_arb {
         struct llist_head requests;
 
         struct gk20a *g;
+        int status;
 
         struct nvgpu_clk_arb_target actual_pool[2];
         struct nvgpu_clk_arb_target *actual;
@@ -269,7 +270,8 @@ int nvgpu_clk_arb_init_arbiter(struct gk20a *g)
                         atomic_read(&arb->req_nr));
         } while (!atomic_read(&arb->req_nr));
 
-        return 0;
+
+        return arb->status;
 
 init_fail:
 
@@ -533,6 +535,7 @@ static int nvgpu_clk_arb_update_vf_table(struct nvgpu_clk_arb *arb)
                         clk_cur = table->mclk_points[j].mhz;
                         j++;
                         num_points++;
+
                 }
         }
         table->mclk_num_points = num_points;
@@ -605,7 +608,7 @@ static void nvgpu_clk_arb_run_vf_table_cb(struct work_struct *work)
         err = clk_vf_point_cache(g);
         if (err) {
                 gk20a_err(dev_from_gk20a(g),
-                        "failed to get GPC2CLK SRAM voltage");
+                        "failed to cache VF table");
                 return;
         }
         nvgpu_clk_arb_update_vf_table(arb);
@@ -625,7 +628,7 @@ static void nvgpu_clk_arb_run_arbiter_cb(struct work_struct *work)
         u32 voltuv, voltuv_sram;
         bool mclk_set, gpc2clk_set;
 
-        int status;
+        int status = 0;
 
         /* Temporary variables for checking target frequency */
         u16 gpc2clk_target, mclk_target;
@@ -742,15 +745,21 @@ static void nvgpu_clk_arb_run_arbiter_cb(struct work_struct *work)
         actual->gpc2clk = gpc2clk_target;
         actual->mclk = mclk_target;
         arb->voltuv_actual = voltuv;
+        arb->status = status;
 
         /* Make changes visible to other threads */
         smp_wmb();
         xchg(&arb->actual, actual);
 
+        /* status must be visible before atomic inc */
+        smp_wmb();
         atomic_inc(&arb->req_nr);
 
         wake_up_interruptible(&arb->request_wq);
 
+        if (status < 0)
+                gk20a_err(dev_from_gk20a(g),
+                        "Error in arbiter update");
 
 #ifdef CONFIG_DEBUG_FS
         g->ops.read_ptimer(g, &t1);
@@ -1016,20 +1025,23 @@ static void nvgpu_clk_arb_find_vf_point(struct nvgpu_clk_arb *arb,
         struct nvgpu_clk_vf_table *table;
         u32 index;
 
-        gpc2clk_target = *gpc2clk;
-        mclk_target = *mclk;
-        gpc2clk_voltuv = 0;
-        gpc2clk_voltuv_sram = 0;
-        mclk_voltuv = 0;
-        mclk_voltuv_sram = 0;
-
         do {
+                gpc2clk_target = *gpc2clk;
+                mclk_target = *mclk;
+                gpc2clk_voltuv = 0;
+                gpc2clk_voltuv_sram = 0;
+                mclk_voltuv = 0;
+                mclk_voltuv_sram = 0;
+
                 table = ACCESS_ONCE(arb->current_vf_table);
                 /* pointer to table can be updated by callback */
                 smp_rmb();
 
                 if (!table)
                         continue;
+                if ((!table->gpc2clk_num_points) || (!table->mclk_num_points))
+                        goto find_exit;
+
                 /* round up the freq requests */
                 for (index = 0; index < table->gpc2clk_num_points; index++) {
                         if (table->gpc2clk_points[index].mhz >=
@@ -1045,10 +1057,10 @@ static void nvgpu_clk_arb_find_vf_point(struct nvgpu_clk_arb *arb,
                 }
 
                 if (index == table->gpc2clk_num_points) {
-                        gpc2clk_target = table->gpc2clk_points[index].mhz;
-                        gpc2clk_voltuv = table->gpc2clk_points[index].uvolt;
+                        gpc2clk_target = table->gpc2clk_points[index-1].mhz;
+                        gpc2clk_voltuv = table->gpc2clk_points[index-1].uvolt;
                         gpc2clk_voltuv_sram =
-                                table->gpc2clk_points[index].uvolt_sram;
+                                table->gpc2clk_points[index-1].uvolt_sram;
                 }
 
                 for (index = 0; index < table->mclk_num_points; index++) {
@@ -1061,14 +1073,15 @@ static void nvgpu_clk_arb_find_vf_point(struct nvgpu_clk_arb *arb,
                         }
                 }
                 if (index == table->mclk_num_points) {
-                        mclk_target = table->mclk_points[index].mhz;
-                        mclk_voltuv = table->mclk_points[index].uvolt;
+                        mclk_target = table->mclk_points[index-1].mhz;
+                        mclk_voltuv = table->mclk_points[index-1].uvolt;
                         mclk_voltuv_sram =
-                                table->mclk_points[index].uvolt_sram;
+                                table->mclk_points[index-1].uvolt_sram;
                 }
         } while (!table ||
                 (ACCESS_ONCE(arb->current_vf_table) != table));
 
+find_exit:
         *voltuv = gpc2clk_voltuv > mclk_voltuv ? gpc2clk_voltuv : mclk_voltuv;
         *voltuv_sram = gpc2clk_voltuv_sram > mclk_voltuv_sram ?
                 gpc2clk_voltuv_sram : mclk_voltuv_sram;
@@ -1136,7 +1149,6 @@ static int nvgpu_clk_arb_change_vf_point(struct gk20a *g, u16 gpc2clk_target,
                 status = clk_program_fll_clks(g, &fllclk);
                 if (status < 0)
                         return status;
-
         }
 
         return 0;