[PATCH 01/12] accel/habanalabs: prevent immediate hard reset due to 2 adjacent H/W events

[Oded Gabbay <ogabbay@kernel.org>]

From: Tomer Tayar <ttayar@habana.ai>

When a H/W event is received while a user is registered to events, no
immediate hard reset will happen, and instead the user will be notified
and will have some time to handle it and eventually release the
device, after which the reset will be done.
If a user, as part of the handling and as part of the cleanup steps
towards releasing the device, unregisters from receiving those events,
and at that time an adjacent H/W event is received, it will be assumed
that the user is not registered to events and thus an immediate hard
reset is required.

To prevent such an unwanted immediate reset, modify the driver to
perform it if the user is not registered to events AND we don't already
have a pending reset for a previous H/W event.

Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
---
 drivers/accel/habanalabs/common/device.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/accel/habanalabs/common/device.c b/drivers/accel/habanalabs/common/device.c
index b97339d1f7c6..1e61e79c42e5 100644
--- a/drivers/accel/habanalabs/common/device.c
+++ b/drivers/accel/habanalabs/common/device.c
@@ -1916,7 +1916,16 @@ int hl_device_cond_reset(struct hl_device *hdev, u32 flags, u64 event_mask)
 	}
 
 	ctx = hl_get_compute_ctx(hdev);
-	if (!ctx || !ctx->hpriv->notifier_event.eventfd)
+	if (!ctx)
+		goto device_reset;
+
+	/*
+	 * There is no point in postponing the reset if user is not registered for events.
+	 * However if no eventfd_ctx exists but the device release watchdog is already scheduled, it
+	 * just implies that user has unregistered as part of handling a previous event. In this
+	 * case an immediate reset is not required.
+	 */
+	if (!ctx->hpriv->notifier_event.eventfd && !hdev->reset_info.watchdog_active)
 		goto device_reset;
 
 	/* Schedule the device release watchdog work unless reset is already in progress or if the
-- 
2.40.1