linux-kernel - [PATCH 29/30] habanalabs: prevent false heartbeat failure during soft-reset

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Date:   Sat, 22 Jan 2022 21:57:30 +0200
From:   Oded Gabbay <ogabbay@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Tomer Tayar <ttayar@...ana.ai>
Subject: [PATCH 29/30] habanalabs: prevent false heartbeat failure during soft-reset

From: Tomer Tayar <ttayar@...ana.ai>

The heartbeat thread is active during soft-reset, and it tries to send
messages to CPU-CP core.
Within the soft-reset, in the time window in which the device is marked
as disabled, any CPU-CP command is "silently" skipped and a success
value it returned.
However, in addition to the return value, the heartbeat function also
checks the F/W result, but because no command is sent in this time
window, the result variable won't hold the expected value and we will
have a false heartbeat failure.

To avoid it, modify the "silent" skip to be done only in hard-reset.
The CPU-CP should be able to handle messages during soft-reset.

In addition to the heartbeat problem, this should also solve other
issues in other flows that send messages during soft-reset and use the
F/W result as it w/o being aware to the reset.

Signed-off-by: Tomer Tayar <ttayar@...ana.ai>
Reviewed-by: Oded Gabbay <ogabbay@...nel.org>
Signed-off-by: Oded Gabbay <ogabbay@...nel.org>
---
 drivers/misc/habanalabs/common/firmware_if.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/habanalabs/common/firmware_if.c b/drivers/misc/habanalabs/common/firmware_if.c
index 39de9d86ee6c..11957d36c6a9 100644
--- a/drivers/misc/habanalabs/common/firmware_if.c
+++ b/drivers/misc/habanalabs/common/firmware_if.c
@@ -214,7 +214,7 @@ int hl_fw_send_cpu_message(struct hl_device *hdev, u32 hw_queue_id, u32 *msg,
 	dma_addr_t pkt_dma_addr;
 	struct hl_bd *sent_bd;
 	u32 tmp, expected_ack_val, pi;
-	int rc = 0;
+	int rc;

 	pkt = hdev->asic_funcs->cpu_accessible_dma_pool_alloc(hdev, len,
 								&pkt_dma_addr);
@@ -228,8 +228,11 @@ int hl_fw_send_cpu_message(struct hl_device *hdev, u32 hw_queue_id, u32 *msg,

 	mutex_lock(&hdev->send_cpu_message_lock);

-	if (hdev->disabled)
+	/* CPU-CP messages can be sent during soft-reset */
+	if (hdev->disabled && !hdev->reset_info.is_in_soft_reset) {
+		rc = 0;
 		goto out;
+	}

 	if (hdev->device_cpu_disabled) {
 		rc = -EIO;
-- 
2.25.1