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Background: In case of a deferred suspend implemented by gk20a_idle, the device waits for a delay before suspending and invoking power gating callbacks. This helps minimize resume latency for any resume calls(gk20a_busy) that occur before the delay. Now, some APIs spread across the driver requires that if the device is powered on, then they can proceed with register writes, but if its powered off, then it must return. Examples of such APIs include l2_flush, fb_flush and even nvs_thread. We have relied on some hacks to ensure the device is kept powered on to prevent any such delayed suspension to proceed. However, this still raced for some calls like ioctl l2_flush, so gk20a_busy() was added (Refer to commit Id dd341e7ecbaf65843cb8059f9d57a8be58952f63) Upstream linux kernel has introduced the API pm_runtime_get_if_active specifically to handle the corner case for locking the state during the event of a deferred suspend. According to the Linux kernel docs, invoking the API with ign_usage_count parameter set to true, prevents an incoming suspend if it has not already suspended. With this, there is no longer a need to check whether nvgpu_is_powered_off(). Changed the behavior of gk20a_busy_noresume() to return bool. It returns true, iff it managed to prevent an imminent suspend, else returns false. For cases where PM runtime is disabled, the code follows the existing implementation. Added missing gk20a_busy_noresume() calls to tlb_invalidate. Also, moved gk20a_pm_deinit to after nvgpu_quiesce() in the module removal path. This is done to prevent regs access after registers are locked out at the end of nvgpu_quiesce. This can happen as some free function calls post quiesce might still have l2_flush, fb_flush deep inside their stack, hence invoke gk20a_pm_deinit to disable pm_runtime immediately after quiesce. Kept the legacy implementation same for VGPU and older kernels Jira NVGPU-8487 Signed-off-by: Debarshi Dutta <ddutta@nvidia.com> Change-Id: I972f9afe577b670c44fc09e3177a5ce8a44ca338 Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2715654 Reviewed-by: Sagar Kamble <skamble@nvidia.com> Reviewed-by: Vijayakumar Subbu <vsubbu@nvidia.com> GVS: Gerrit_Virtual_Submit