gpu: nvgpu: use railgate instead of reset_assert

In gk20a_do_idle(), if can_railgate = false, we do
reset_assert() on the GPU

But asserting reset might have dependencies on
specific h/w seqeunce for ensuring proper reset

Hence avoid calling reset_assert() and directly
call platform specific unrailgate() and railgate()
APIs which take care of the correct reset sequence

Bug 200142989
Bug 200137963
Bug 1678611

Change-Id: Ide886dd88b8422ad36de52d54378b1edd9c7bbd6
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/820322
(cherry picked from commit d621ddd49da976a75c14aa7aaa37f700fb4e83f2)
Reviewed-on: http://git-master/r/822515
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Sachin Nikam <snikam@nvidia.com>

1 files changed, 12 insertions, 10 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/gk20a.c b/drivers/gpu/nvgpu/gk20a/gk20a.c
index a44ce996..0d74099e 100644
--- a/drivers/gpu/nvgpu/gk20a/gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/gk20a.c
@@ -1854,23 +1854,23 @@ int __gk20a_do_idle(struct platform_device *pdev, bool force_reset)
         } else {
                 /*
                  * Case 2 : GPU railgate is not supported or we explicitly
-                 * do not want to do railgate
+                 * do not want to depend on runtime PM
                  *
                  * if GPU is now idle, call prepare_poweroff() to save the
-                 * state and then assert the reset
+                 * state and then do explicit railgate
                  *
-                 * __gk20a_do_unidle() needs to deassert reset, call
+                 * __gk20a_do_unidle() needs to unrailgate, call
                  * finalize_poweron(), and then call pm_runtime_put_sync()
                  * to balance the GPU usage counter
                  */
-                if (!platform->reset_assert || !platform->reset_deassert)
-                        goto fail_drop_usage_count;
 
                 /* Save the GPU state */
                 gk20a_pm_prepare_poweroff(&pdev->dev);
 
-                /* assert GPU reset */
-                platform->reset_assert(pdev);
+                gk20a_pm_disable_clk(&pdev->dev);
+
+                /* railgate GPU */
+                platform->railgate(pdev);
 
                 udelay(10);
 
@@ -1915,10 +1915,12 @@ int __gk20a_do_unidle(struct platform_device *pdev)
 
         if (g->forced_reset) {
                 /*
-                 * If we did a reset (and not railgate),
-                 * then deassert the GPU reset here first
+                 * If we did a forced-reset/railgate
+                 * then unrailgate the GPU here first
                  */
-                platform->reset_deassert(pdev);
+                platform->unrailgate(pdev);
+
+                gk20a_pm_enable_clk(&pdev->dev);
 
                 /* restore the GPU state */
                 gk20a_pm_finalize_poweron(&pdev->dev);