Bluetooth: hci_bcm: Add support for FW loading in autobaud mode

Use the presence of a DT property, "brcm,requires-autobaud-mode", to enable
startup in autobaud mode. If the property is present, the device is started
in autobaud mode by asserting RTS (BT_UART_CTS_N) prior to powering on the
device.

Also prevent the use of unsupported commands for devices started in
autobaud mode. Only a limited subset of HCI commands are supported in
autobaud mode.

Some devices (e.g. CYW5557x) require autobaud mode to enable FW loading.
Autobaud mode can also be required on some boards where the controller
device is using a non-standard baud rate in normal mode when first powered
on.

Signed-off-by: Hakan Jansson <[e-mail]>
Signed-off-by: Marcel Holtmann <[e-mail]>

drivers/bluetooth/btbcm.c

···
 	bt_dev_info(hdev, "BCM: chip id %u", skb->data[1]);
 	kfree_skb(skb);
 
+	return 0;
+}
+
+static int btbcm_print_controller_features(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+
 	/* Read Controller Features */
 	skb = btbcm_read_controller_features(hdev);
 	if (IS_ERR(skb))
···
 #endif
 }
 
-int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done)
+int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done, bool use_autobaud_mode)
 {
 	u16 subver, rev, pid, vid;
 	struct sk_buff *skb;
···
 		if (err)
 			return err;
 	}
-	err = btbcm_print_local_name(hdev);
-	if (err)
-		return err;
+
+	if (!use_autobaud_mode) {
+		err = btbcm_print_controller_features(hdev);
+		if (err)
+			return err;
+
+		err = btbcm_print_local_name(hdev);
+		if (err)
+			return err;
+	}
 
 	bcm_subver_table = (hdev->bus == HCI_USB) ? bcm_usb_subver_table :
 						    bcm_uart_subver_table;
···
 }
 EXPORT_SYMBOL_GPL(btbcm_initialize);
 
-int btbcm_finalize(struct hci_dev *hdev, bool *fw_load_done)
+int btbcm_finalize(struct hci_dev *hdev, bool *fw_load_done, bool use_autobaud_mode)
 {
 	int err;
 
 	/* Re-initialize if necessary */
 	if (*fw_load_done) {
-		err = btbcm_initialize(hdev, fw_load_done);
+		err = btbcm_initialize(hdev, fw_load_done, use_autobaud_mode);
 		if (err)
 			return err;
 	}
···
 int btbcm_setup_patchram(struct hci_dev *hdev)
 {
 	bool fw_load_done = false;
+	bool use_autobaud_mode = false;
 	int err;
 
 	/* Initialize */
-	err = btbcm_initialize(hdev, &fw_load_done);
+	err = btbcm_initialize(hdev, &fw_load_done, use_autobaud_mode);
 	if (err)
 		return err;
 
 	/* Re-initialize after loading Patch */
-	return btbcm_finalize(hdev, &fw_load_done);
+	return btbcm_finalize(hdev, &fw_load_done, use_autobaud_mode);
 }
 EXPORT_SYMBOL_GPL(btbcm_setup_patchram);
 

drivers/bluetooth/btbcm.h

···
 int btbcm_setup_patchram(struct hci_dev *hdev);
 int btbcm_setup_apple(struct hci_dev *hdev);
 
-int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done);
-int btbcm_finalize(struct hci_dev *hdev, bool *fw_load_done);
+int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done, bool use_autobaud_mode);
+int btbcm_finalize(struct hci_dev *hdev, bool *fw_load_done, bool use_autobaud_mode);
 
 #else
 
···
 	return 0;
 }
 
-static inline int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done)
+static inline int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done, bool use_autobaud_mode)
 {
 	return 0;
 }
 
-static inline int btbcm_finalize(struct hci_dev *hdev, bool *fw_load_done)
+static inline int btbcm_finalize(struct hci_dev *hdev, bool *fw_load_done, bool use_autobaud_mode)
 {
 	return 0;
 }

drivers/bluetooth/hci_bcm.c

···
  * @no_early_set_baudrate: don't set_baudrate before setup()
  * @drive_rts_on_open: drive RTS signal on ->open() when platform requires it
  * @pcm_int_params: keep the initial PCM configuration
+ * @use_autobaud_mode: start Bluetooth device in autobaud mode
  */
 struct bcm_device {
 	/* Must be the first member, hci_serdev.c expects this. */
···
 #endif
 	bool			no_early_set_baudrate;
 	bool			drive_rts_on_open;
+	bool			use_autobaud_mode;
 	u8			pcm_int_params[5];
 };
 
···
 
 out:
 	if (bcm->dev) {
-		if (bcm->dev->drive_rts_on_open)
+		if (bcm->dev->use_autobaud_mode)
+			hci_uart_set_flow_control(hu, false);	/* Assert BT_UART_CTS_N */
+		else if (bcm->dev->drive_rts_on_open)
 			hci_uart_set_flow_control(hu, true);
 
 		hu->init_speed = bcm->dev->init_speed;
···
 {
 	struct bcm_data *bcm = hu->priv;
 	bool fw_load_done = false;
+	bool use_autobaud_mode = (bcm->dev ? bcm->dev->use_autobaud_mode : 0);
 	unsigned int speed;
 	int err;
 
···
 	hu->hdev->set_diag = bcm_set_diag;
 	hu->hdev->set_bdaddr = btbcm_set_bdaddr;
 
-	err = btbcm_initialize(hu->hdev, &fw_load_done);
+	err = btbcm_initialize(hu->hdev, &fw_load_done, use_autobaud_mode);
 	if (err)
 		return err;
 
···
 		btbcm_write_pcm_int_params(hu->hdev, &params);
 	}
 
-	err = btbcm_finalize(hu->hdev, &fw_load_done);
+	err = btbcm_finalize(hu->hdev, &fw_load_done, use_autobaud_mode);
 	if (err)
 		return err;
 
···
 
 static int bcm_of_probe(struct bcm_device *bdev)
 {
+	bdev->use_autobaud_mode = device_property_read_bool(bdev->dev,
+							    "brcm,requires-autobaud-mode");
+	if (bdev->use_autobaud_mode)
+		bdev->no_early_set_baudrate = true;
+
 	device_property_read_u32(bdev->dev, "max-speed", &bdev->oper_speed);
 	device_property_read_u8_array(bdev->dev, "brcm,bt-pcm-int-params",
 				      bdev->pcm_int_params, 5);