[RFC v1 6/8] Bluetooth: hci_h5: add support for Realtek UART Bluetooth modules

[Marcel Holtmann]

Hi Martin,

> Realtek RTL8723BS and RTL8723DS are SDIO wifi chips with an embedded
> Bluetooth controller which connects to the host via UART.
> The H5 protocol is used for communication between host and device.
> 
> The Realtek "rtl8723bs_bt" and "rtl8723ds_bt" userspace Bluetooth UART
> initialization tools (rtk_hciattach) use the following sequence:
> 1) send H5 sync pattern (already supported by hci_h5)
> 2) get LMP version (already supported by btrtl)
> 3) get ROM version (already supported by btrtl)
> 4) load the firmware and config for the current chipset (already
>   supported by btrtl)
> 5) read UART settings from the config blob (already supported by btrtl)
> 6) send UART settings via a vendor command to the device (which changes
>   the baudrate of the device and enables or disables flow control
>   depending on the config)
> 7) change the baudrate and flow control settings on the host
> 8) send the firmware and config blob to the device (already supported by
>   btrtl)
> 
> This uses the serdev library as well as the existing btrtl driver to
> initialize the Bluetooth functionality, which consists of:
> - identifying the device and loading the corresponding firmware and
>  config blobs (steps #2, #3 and #4)
> - configuring the baudrate and flow control (steps #6 and #7)
> - uploading the firmware to the device (step #8)
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
> ---
> drivers/bluetooth/Kconfig  |   1 +
> drivers/bluetooth/hci_h5.c | 195 ++++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 195 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bluetooth/Kconfig b/drivers/bluetooth/Kconfig
> index 60e1c7d6986d..3001f1200c72 100644
> --- a/drivers/bluetooth/Kconfig
> +++ b/drivers/bluetooth/Kconfig
> @@ -146,6 +146,7 @@ config BT_HCIUART_LL
> config BT_HCIUART_3WIRE
> 	bool "Three-wire UART (H5) protocol support"
> 	depends on BT_HCIUART
> +	select BT_RTL if SERIAL_DEV_BUS
> 	help
> 	  The HCI Three-wire UART Transport Layer makes it possible to
> 	  user the Bluetooth HCI over a serial port interface. The HCI

so I just posted a bt3wire.c driver that is serdev only and written from scratch. On a RPi3 Broadcom chip it kinda works. I think there is a lot of extra work to be done, but this might be a better starting point for Realtek UART devices.

Regards

Marcel