gpu: nvgpu: force idle if railgate not supported

Add a way to force idle and reset the GPU in case where GPU
rail gating is not supported
(i.e. platform->can_railgate = false)

In this case, we follow below sequence :
- once GPU is idle, get runtime reference which enables the clocks
- call prepare_poweroff() to save the state explicitly
- perform explicit reset assert/deassert
- call finalize_poweron() to restore the state
- drop the runtime reference taken earlier

Bug 1525284

Change-Id: Id5f3ec152093acd585631dfbf785d8e0561f9048
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/435620
GVS: Gerrit_Virtual_Submit
Reviewed-by: Arto Merilainen <amerilainen@nvidia.com>
Tested-by: Arto Merilainen <amerilainen@nvidia.com>

2 files changed, 36 insertions, 15 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/gk20a.c b/drivers/gpu/nvgpu/gk20a/gk20a.c
index cd104580..c69df460 100644
--- a/drivers/gpu/nvgpu/gk20a/gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/gk20a.c
@@ -1743,9 +1743,6 @@ int gk20a_do_idle(void)
         int ref_cnt;
         bool is_railgated;
 
-        if (!platform->can_railgate)
-                return -ENOSYS;
-
         /* acquire busy lock to block other busy() calls */
         down_write(&g->busy_lock);
 
@@ -1772,25 +1769,39 @@ int gk20a_do_idle(void)
 
         /*
          * if GPU is now idle, we will have only one ref count
-         * drop this ref which will rail gate the GPU
+         * drop this ref which will rail gate the GPU (if GPU
+         * railgate is supported)
+         * if GPU railgate is not supported then we need to
+         * explicitly reset it
          */
         pm_runtime_put_sync(&pdev->dev);
 
-        /* add sufficient delay to allow GPU to rail gate */
-        msleep(platform->railgate_delay);
+        if (platform->can_railgate) {
+                /* add sufficient delay to allow GPU to rail gate */
+                msleep(platform->railgate_delay);
 
-        timeout = jiffies + msecs_to_jiffies(GK20A_WAIT_FOR_IDLE_MS);
+                timeout = jiffies + msecs_to_jiffies(GK20A_WAIT_FOR_IDLE_MS);
 
-        /* check in loop if GPU is railgated or not */
-        do {
-                msleep(1);
-                is_railgated = platform->is_railgated(pdev);
-        } while (!is_railgated && time_before(jiffies, timeout));
+                /* check in loop if GPU is railgated or not */
+                do {
+                        msleep(1);
+                        is_railgated = platform->is_railgated(pdev);
+                } while (!is_railgated && time_before(jiffies, timeout));
+
+                if (is_railgated)
+                        return 0;
+                else
+                        goto fail_timeout;
+        } else {
+                pm_runtime_get_sync(&pdev->dev);
+                gk20a_pm_prepare_poweroff(&pdev->dev);
+
+                tegra_periph_reset_assert(platform->clk[0]);
+                udelay(10);
 
-        if (is_railgated)
+                g->forced_reset = true;
                 return 0;
-        else
-                goto fail_timeout;
+        }
 
 fail:
         pm_runtime_put_noidle(&pdev->dev);
@@ -1811,6 +1822,15 @@ int gk20a_do_unidle(void)
         struct gk20a *g = get_gk20a(pdev);
         struct gk20a_platform *platform = dev_get_drvdata(&pdev->dev);
 
+        if (g->forced_reset) {
+                tegra_periph_reset_deassert(platform->clk[0]);
+
+                gk20a_pm_finalize_poweron(&pdev->dev);
+                pm_runtime_put_sync(&pdev->dev);
+
+                g->forced_reset = false;
+        }
+
         /* release the lock and open up all other busy() calls */
         mutex_unlock(&platform->railgate_lock);
         up_write(&g->busy_lock);
diff --git a/drivers/gpu/nvgpu/gk20a/gk20a.h b/drivers/gpu/nvgpu/gk20a/gk20a.h
index 55bc6b20..774e4e85 100644
--- a/drivers/gpu/nvgpu/gk20a/gk20a.h
+++ b/drivers/gpu/nvgpu/gk20a/gk20a.h
@@ -271,6 +271,7 @@ struct gk20a {
         bool elpg_enabled;
         bool aelpg_enabled;
         bool forced_idle;
+        bool forced_reset;
 
 #ifdef CONFIG_DEBUG_FS
         spinlock_t debugfs_lock;