Re: How to enable hci0 for bcm4356 chip on htc m9?

[Marcel Holtmann <marcel@holtmann.org>]

Hi Qingtao,

> I've figured out how to enable hci0 for bcm4356 chipset on Linux other
> than android. Turns out the bluedroid in CyanogenMod android for htc
> m9 phone no longer uses bluez and its dbus interfaces any longer, no
> wonder there is no hci0 found there.
> 
> Turns out broadcom wifi/bt/fm chipset needs a special program to
> download the required "mini driver" or *.hcd file to it at system
> startup. Previously I tried to extract relevant code from broadcom's
> libbt-vendor.so implementation for bluedroid, it was on the correct
> direction but I hadn't unveiled all needed code. Turns out there is a
> open source program for this purpose already, brcm_patchram_plus,
> which could bring about the hci0 interface by the following command:
> 
> ./brcm_patchram_plus -d --patchram
> /system/etc/firmware/BCM4354A2_001.003.015.0064.0175.hcd --no2bytes
> --baudrate 4000000 --use_baudrate_for_download --bd_addr
> 90:E7:C4:F3:F7:09 --enable_hci --scopcm=0,4,0,0,0,1,0,3,0,0
> /dev/ttyHS0 &
> 
> Please note that bluetooth kernel driver needs to enable HCIUART and
> HCIUART_H4 options to  activate relevant tty driver for the HCI-UART
> interface. Of course, before running the above program, the bluetooth
> hardware functionality should be powered on by "rfkill unblock
> bluetooth" command, or directly writing 1 into relevant
> /sys/class/rfkill/rfkillN/state file.
> 
> Moreover, if the --scopcm option needs to be changed, the process of
> brcm_patchram_plus can be killed and restarted, however, I found that
> I also need to block and then unblock the bluetooth via rfkill command
> otherwise it will fail to download the mini drivers in the hcd file.
> 
> Last but not least, please note that the --scopcm option is not
> working for me at the time being. I've already specified SCORouting =
> PCM in audio.conf, but SCO-over-PCM doesn't work for me and I can't
> hear anything from a connected bluetooth headset. Only change the SCO
> routing to HCI (also requires the first byte, sco_routing, in the
> --scopcm option, set to 1) would I hear some sound through the
> headset, however, unfortunately, they are simply noise.

we added hci_bcm.c kernel driver for driving Broadcom chips. We use it for some Broadcom UART based chips that are enumerated via ACPI. For DT we are still missing support, but should be easy to add. And then it will do the proper baud rate setup, patchram download etc.

Regards

Marcel