linux-kernel - [PATCH v8] Bluetooth: hci_qca: Fix SSR (SubSystem Restart) fail when BT

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Message-Id: <20250822123605.757306-1-quic_shuaz@quicinc.com>
Date: Fri, 22 Aug 2025 20:36:05 +0800
From: Shuai Zhang <quic_shuaz@...cinc.com>
To: dmitry.baryshkov@....qualcomm.com, marcel@...tmann.org,
        luiz.dentz@...il.com
Cc: linux-bluetooth@...r.kernel.org, stable@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_chejiang@...cinc.com, Shuai Zhang <quic_shuaz@...cinc.com>
Subject: [PATCH v8] Bluetooth: hci_qca: Fix SSR (SubSystem Restart) fail when BT_EN is pulled up by hw

When the host actively triggers SSR and collects coredump data,
the Bluetooth stack sends a reset command to the controller. However, due
to the inability to clear the QCA_SSR_TRIGGERED and QCA_IBS_DISABLED bits,
the reset command times out.

To address this, this patch clears the QCA_SSR_TRIGGERED and
QCA_IBS_DISABLED flags and adds a 50ms delay after SSR, but only when
HCI_QUIRK_NON_PERSISTENT_SETUP is not set. This ensures the controller
completes the SSR process when BT_EN is always high due to hardware.

For the purpose of HCI_QUIRK_NON_PERSISTENT_SETUP, please refer to
the comment in `include/net/bluetooth/hci.h`.

The HCI_QUIRK_NON_PERSISTENT_SETUP quirk is associated with BT_EN,
and its presence can be used to determine whether BT_EN is defined in DTS.

After SSR, host will not download the firmware, causing
controller to remain in the IBS_WAKE state. Host needs
to synchronize with the controller to maintain proper operation.

Multiple triggers of SSR only first generate coredump file,
due to memcoredump_flag no clear.

add clear coredump flag when ssr completed.

When the SSR duration exceeds 2 seconds, it triggers
host tx_idle_timeout, which sets host TX state to sleep. due to the
hardware pulling up bt_en, the firmware is not downloaded after the SSR.
As a result, the controller does not enter sleep mode. Consequently,
when the host sends a command afterward, it sends 0xFD to the controller,
but the controller does not respond, leading to a command timeout.

So reset tx_idle_timer after SSR to prevent host enter TX IBS_Sleep mode.

Changes since v6-7:
- Merge the changes into a single patch.
- Update commit.

Changes since v1-5:
- Add an explanation for HCI_QUIRK_NON_PERSISTENT_SETUP.
- Add commments for msleep(50).
- Update format and commit.

Signed-off-by: Shuai Zhang <quic_shuaz@...cinc.com>
---
 drivers/bluetooth/hci_qca.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
index 4e56782b0..9dc59b002 100644
--- a/drivers/bluetooth/hci_qca.c
+++ b/drivers/bluetooth/hci_qca.c
@@ -1653,6 +1653,39 @@ static void qca_hw_error(struct hci_dev *hdev, u8 code)
 		skb_queue_purge(&qca->rx_memdump_q);
 	}

+	/*
+	 * If the BT chip's bt_en pin is connected to a 3.3V power supply via
+	 * hardware and always stays high, driver cannot control the bt_en pin.
+	 * As a result, during SSR (SubSystem Restart), QCA_SSR_TRIGGERED and
+	 * QCA_IBS_DISABLED flags cannot be cleared, which leads to a reset
+	 * command timeout.
+	 * Add an msleep delay to ensure controller completes the SSR process.
+	 *
+	 * Host will not download the firmware after SSR, controller to remain
+	 * in the IBS_WAKE state, and the host needs to synchronize with it
+	 *
+	 * Since the bluetooth chip has been reset, clear the memdump state.
+	 */
+	if (!test_bit(HCI_QUIRK_NON_PERSISTENT_SETUP, &hdev->quirks)) {
+		/*
+		 * When the SSR (SubSystem Restart) duration exceeds 2 seconds,
+		 * it triggers host tx_idle_delay, which sets host TX state
+		 * to sleep. Reset tx_idle_timer after SSR to prevent
+		 * host enter TX IBS_Sleep mode.
+		 */
+		mod_timer(&qca->tx_idle_timer, jiffies +
+				  msecs_to_jiffies(qca->tx_idle_delay));
+
+		/* Controller reset completion time is 50ms */
+		msleep(50);
+
+		clear_bit(QCA_SSR_TRIGGERED, &qca->flags);
+		clear_bit(QCA_IBS_DISABLED, &qca->flags);
+
+		qca->tx_ibs_state = HCI_IBS_TX_AWAKE;
+		qca->memdump_state = QCA_MEMDUMP_IDLE;
+	}
+
 	clear_bit(QCA_HW_ERROR_EVENT, &qca->flags);
 }

-- 
2.34.1