[PATCH v2 2/3] Bluetooth: btintel_pcie: sync mbox tlv parsing with GP0 alive interrupt

[Kiran K <kiran.k@intel.com>]

Performing a target access to read the mbox TLV table while the driver
is concurrently posting RX buffers to the firmware causes the hardware
to return 0 for the target address, resulting in an invalid/empty TLV
parse.

Add a synchronization handshake between the mbox TLV read operation
performed by the mbox worker and the GP0 (alive) MSI-X interrupt (which
signals completion of RX buffer posting). The worker now waits for the
alive interrupt before initiating the target access, ensuring the
hardware returns valid data.

Assisted-by: Gemini:gemini-3.1-pro-preview
Signed-off-by: Kiran K <kiran.k@intel.com>
---
changes in v2:
 - No code change

 drivers/bluetooth/btintel_pcie.c | 42 +++++++++++++++++++++++++++++---
 drivers/bluetooth/btintel_pcie.h | 10 +++++++-
 2 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/drivers/bluetooth/btintel_pcie.c b/drivers/bluetooth/btintel_pcie.c
index 4d1b6e9a2bdc..bbce41b5b376 100644
--- a/drivers/bluetooth/btintel_pcie.c
+++ b/drivers/bluetooth/btintel_pcie.c
@@ -987,6 +987,24 @@ static int btintel_parse_mbox_tlv(struct btintel_pcie_data *data)
 	struct mbox_tlv *tlv;
 	struct btintel_data *cnvi_data = hci_get_priv(data->hdev);
 	u8 hw_variant = INTEL_HW_VARIANT(cnvi_data->cnvi_bt);
+	long t;
+
+	/* Wait for GP0 alive interrupt to post RX buffers */
+	t = wait_event_timeout(data->mbox_parse_wait_q,
+			       test_bit(BTINTEL_PCIE_MBOX_PARSE_READY, &data->flags),
+			       msecs_to_jiffies(BTINTEL_PCIE_MBOX_INTR_TIMEOUT_MS));
+	if (!t) {
+		bt_dev_warn(data->hdev,
+			    "Timeout (%u ms) waiting for alive interrupt before mbox TLV parse; skipping",
+			    BTINTEL_PCIE_MBOX_INTR_TIMEOUT_MS);
+		return 0;
+	}
+	clear_bit(BTINTEL_PCIE_MBOX_PARSE_READY, &data->flags);
+
+	bt_dev_info(data->hdev,
+		    "mbox TLV parse started at %lld ns (%lld us after mbox interrupt)",
+		    ktime_to_ns(ktime_get()),
+		    ktime_to_us(ktime_sub(ktime_get(), data->mbox_intr_ts)));
 
 	memset(&data->dump_info, 0, sizeof(data->dump_info));
 
@@ -1230,12 +1248,22 @@ static void btintel_pcie_msix_gp1_handler(struct btintel_pcie_data *data)
 	if (target_access &&
 	    !test_and_set_bit(BTINTEL_PCIE_MAIL_BOX_INTR,
 				   &data->flags)) {
+		/* Arm the mbox<->alive handshake */
+		clear_bit(BTINTEL_PCIE_MBOX_PARSE_READY, &data->flags);
+		set_bit(BTINTEL_PCIE_MBOX_PARSE_PENDING, &data->flags);
+		data->mbox_intr_ts = ktime_get();
+
+		bt_dev_info(data->hdev,
+			    "mbox interrupt received at %lld ns; queuing mbox_work",
+			    ktime_to_ns(data->mbox_intr_ts));
+
 		WRITE_ONCE(data->debug_table_addr, addr);
 		WRITE_ONCE(data->debug_table_size, size);
 		if (!queue_work(data->dump_workqueue,
-				&data->mbox_work))
-			clear_bit(BTINTEL_PCIE_MAIL_BOX_INTR,
-				  &data->flags);
+				&data->mbox_work)) {
+			clear_bit(BTINTEL_PCIE_MAIL_BOX_INTR, &data->flags);
+			clear_bit(BTINTEL_PCIE_MBOX_PARSE_PENDING, &data->flags);
+		}
 	}
 
 	/* Mailbox is read, ack to FW */
@@ -1345,6 +1373,12 @@ static void btintel_pcie_msix_gp0_handler(struct btintel_pcie_data *data)
 	if (submit_rx) {
 		btintel_pcie_reset_ia(data);
 		btintel_pcie_start_rx(data);
+
+		/* Complete the mbox<->alive handshake */
+		if (test_and_clear_bit(BTINTEL_PCIE_MBOX_PARSE_PENDING, &data->flags)) {
+			set_bit(BTINTEL_PCIE_MBOX_PARSE_READY, &data->flags);
+			wake_up(&data->mbox_parse_wait_q);
+		}
 	}
 
 	if (signal_waitq) {
@@ -3301,6 +3335,8 @@ static int btintel_pcie_probe(struct pci_dev *pdev,
 	init_waitqueue_head(&data->tx_wait_q);
 	data->tx_wait_done = false;
 
+	init_waitqueue_head(&data->mbox_parse_wait_q);
+
 	data->workqueue = alloc_ordered_workqueue(KBUILD_MODNAME, WQ_HIGHPRI);
 	if (!data->workqueue)
 		return -ENOMEM;
diff --git a/drivers/bluetooth/btintel_pcie.h b/drivers/bluetooth/btintel_pcie.h
index 5ceb2ba1276f..5aff1dfa888f 100644
--- a/drivers/bluetooth/btintel_pcie.h
+++ b/drivers/bluetooth/btintel_pcie.h
@@ -125,7 +125,9 @@ enum {
 	BTINTEL_PCIE_FWTRIGGER_DUMP_INPROGRESS,
 	BTINTEL_PCIE_RECOVERY_IN_PROGRESS,
 	BTINTEL_PCIE_SETUP_DONE,
-	BTINTEL_PCIE_MAIL_BOX_INTR
+	BTINTEL_PCIE_MAIL_BOX_INTR,
+	BTINTEL_PCIE_MBOX_PARSE_PENDING,
+	BTINTEL_PCIE_MBOX_PARSE_READY
 };
 
 enum btintel_pcie_tlv_type {
@@ -178,6 +180,7 @@ enum btintel_pcie_mbox_msg {
 
 /* Default interrupt timeout in msec */
 #define BTINTEL_DEFAULT_INTR_TIMEOUT_MS	3000
+#define BTINTEL_PCIE_MBOX_INTR_TIMEOUT_MS	500
 
 #define BTINTEL_PCIE_DX_TRANSITION_MAX_RETRIES	3
 
@@ -588,6 +591,11 @@ struct btintel_pcie_data {
 	u32	debug_table_size;
 	struct btintel_pcie_dump_mem_info	dump_info;
 	struct btintel_pcie_mbox	mbox;
+
+	/* Wait queue for mbox_worker to wait for GP0 alive interrupt */
+	wait_queue_head_t	mbox_parse_wait_q;
+	/* Timestamp captured in GP1 handler when mbox interrupt is received */
+	ktime_t	mbox_intr_ts;
 };
 
 static inline u32 btintel_pcie_rd_reg32(struct btintel_pcie_data *data,
-- 
2.54.0