[PATCH v3] Bluetooth: btintel: read ROM debug registers on FW download failure

[Ravindra <ravindra@intel.com>]

The bootloader records init sequence progress and debug info in four
core debug registers, useful for debugging FW download failures.

Add btintel_get_rom_debug_info() to issue BTINTEL_GET_ROM_DEBUG_INFO
(0xfcde) and log these registers, and invoke it from every FW download
failure and timeout path: btintel_download_fw() (legacy .sfi flow) and
btintel_prepare_fw_download_tlv() (TLV flow), before resetting to the
bootloader.

Tested by corrupting the operational firmware file to force a
download timeout; the driver logged the debug registers on each
failure and retry, e.g.:

  Bluetooth: hci0: Firmware loading timeout
  Bluetooth: Intel get rom debug info:
    dr0:0x80000001 dr1:0x00000000 dr2:0x00000001 dr3:0x00df0071

Signed-off-by: Ravindra <ravindra@intel.com>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
---
 drivers/bluetooth/btintel.c | 47 +++++++++++++++++++++++++++++++++++--
 drivers/bluetooth/btintel.h |  9 +++++++
 2 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/btintel.c b/drivers/bluetooth/btintel.c
index 964d2de30e65..5e6d1ddc99c6 100644
--- a/drivers/bluetooth/btintel.c
+++ b/drivers/bluetooth/btintel.c
@@ -963,6 +963,41 @@ int btintel_send_intel_reset(struct hci_dev *hdev, u32 boot_param)
 }
 EXPORT_SYMBOL_GPL(btintel_send_intel_reset);
 
+static void btintel_get_rom_debug_info(struct hci_dev *hdev)
+{
+	struct btintel_rp_get_rom_debug_info *rom_debug_info;
+	struct sk_buff *skb;
+
+	skb = __hci_cmd_sync(hdev, BTINTEL_GET_ROM_DEBUG_INFO, 0, NULL,
+			     HCI_CMD_TIMEOUT);
+	if (IS_ERR(skb)) {
+		bt_dev_err(hdev, "Failed to send Intel get rom debug info command (%ld)",
+			   PTR_ERR(skb));
+		return;
+	}
+
+	if (skb->len != sizeof(*rom_debug_info)) {
+		bt_dev_err(hdev,
+			   "Intel get rom debug info size mismatch (%u != %zu)",
+			   skb->len, sizeof(*rom_debug_info));
+		kfree_skb(skb);
+		return;
+	}
+
+	rom_debug_info = (struct btintel_rp_get_rom_debug_info *)skb->data;
+
+	/* A non-zero status here would have already been turned into an
+	 * error by the HCI core and reported via the IS_ERR(skb) check above.
+	 */
+	bt_dev_info(hdev, "Intel get rom debug info: dr0:0x%08x dr1:0x%08x dr2:0x%08x dr3:0x%08x",
+		    le32_to_cpu(rom_debug_info->debug_reg0),
+		    le32_to_cpu(rom_debug_info->debug_reg1),
+		    le32_to_cpu(rom_debug_info->debug_reg2),
+		    le32_to_cpu(rom_debug_info->debug_reg3));
+
+	kfree_skb(skb);
+}
+
 int btintel_read_boot_params(struct hci_dev *hdev,
 			     struct intel_boot_params *params)
 {
@@ -2212,6 +2247,8 @@ static int btintel_download_fw(struct hci_dev *hdev,
 			goto done;
 		}
 
+		btintel_get_rom_debug_info(hdev);
+
 		/* When FW download fails, send Intel Reset to retry
 		 * FW download.
 		 */
@@ -2231,8 +2268,10 @@ static int btintel_download_fw(struct hci_dev *hdev,
 	 * of this device.
 	 */
 	err = btintel_download_wait(hdev, calltime, 5000);
-	if (err == -ETIMEDOUT)
+	if (err == -ETIMEDOUT) {
+		btintel_get_rom_debug_info(hdev);
 		btintel_reset_to_bootloader(hdev);
+	}
 
 done:
 	release_firmware(fw);
@@ -2465,6 +2504,8 @@ static int btintel_prepare_fw_download_tlv(struct hci_dev *hdev,
 			goto done;
 		}
 
+		btintel_get_rom_debug_info(hdev);
+
 		/* When FW download fails, send Intel Reset to retry
 		 * FW download.
 		 */
@@ -2484,8 +2525,10 @@ static int btintel_prepare_fw_download_tlv(struct hci_dev *hdev,
 	 * of this device.
 	 */
 	err = btintel_download_wait(hdev, calltime, 5000);
-	if (err == -ETIMEDOUT)
+	if (err == -ETIMEDOUT) {
+		btintel_get_rom_debug_info(hdev);
 		btintel_reset_to_bootloader(hdev);
+	}
 
 done:
 	intel_data->cnvi_bt = ver->cnvi_bt;
diff --git a/drivers/bluetooth/btintel.h b/drivers/bluetooth/btintel.h
index c00f793d9dc8..b3c4c6f87424 100644
--- a/drivers/bluetooth/btintel.h
+++ b/drivers/bluetooth/btintel.h
@@ -178,6 +178,15 @@ struct hci_ppag_enable_cmd {
 	__le32	ppag_enable_flags;
 } __packed;
 
+#define BTINTEL_GET_ROM_DEBUG_INFO	0xfcde
+struct btintel_rp_get_rom_debug_info {
+	__u8	status;
+	__le32	debug_reg0;
+	__le32	debug_reg1;
+	__le32	debug_reg2;
+	__le32	debug_reg3;
+} __packed;
+
 #define INTEL_TLV_TYPE_ID		0x01
 
 #define INTEL_TLV_SYSTEM_EXCEPTION	0x00
-- 
2.43.0