Device Driver Interface of WiLink Solution

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Hardware Interface and MUX mode configuration

The WiLink connectivity chip's BT, FM and GPS IPs are interfaced with the application processor (OMAP) through UARTs. A GPIO line called nShutDown acts as the chip enable line for the connectivity chip.

Also, the connectivity chip is interfaced to BT core via PCM lines (mcbsp if OMAP) and to the FM core via i2S (or PCM). The BT-PCM lines carry the voice data during a call scenario. The FM i2S lines can be used for FM Rx audio (digital) or FM Tx audio.

The mux-mode configurations of these hardware interfaces can be configured via the OMAP MUX framework supported by the BSP as follows:

Example 1: On Zoom3 the N-Shut-Down line is connected to GPIO 109.

In file arch/arm/mach-omap2/board-zoom3.c you would find the following entry:
        omap_mux_init_gpio(109, OMAP_PIN_OUTPUT);

The configuration can be done in x-loader or u-boot. Note that the configuration may not take place in u-boot if it is already being done in x-loader.

Example 2: On OMAP3SDP/Blaze's x-loader, the McBSP1 is connected to the BT-PCM lines.

In file board/omap4430sdp/omap4430sdp.c of the ''u-boot'' source code, you will find entries which look like:

        MV(CP(ABE_MCBSP1_DX),   (OFF_EN | OFF_OUT_PTD | M0)) /* abe_mcbsp1_dx */ \
        MV(CP(ABE_MCBSP1_FSX),  (IEN | OFF_EN | OFF_PD | OFF_IN | M0)) /* abe_mcbsp1_fsx */ \
        MV(CP(ABE_MCBSP1_DX),   (OFF_EN | OFF_OUT_PTD | M0)) /* abe_mcbsp1_dx */ \
        MV(CP(ABE_MCBSP1_FSX),  (IEN | OFF_EN | OFF_PD | OFF_IN | M0)) /* abe_mcbsp1_fsx */ \

Example 3: On OMAP4SDP/Blaze, the OMAP UART2 is connected to the BT-HCI-UART.

        MV(CP(UART2_CTS),       (PTU | IEN | M0)) /* uart2_cts */ \
        MV(CP(UART2_RTS),       (M0)) /* uart2_rts */ \
        MV(CP(UART2_RX),        (IEN | M0)) /* uart2_rx */ \
        MV(CP(UART2_TX),        (M0)) /* uart2_tx */ \

Note: Since there lacks a standard way to configure the hardware interfaces, please look into relevant BSP or contact the email ID mentioned below.

Shared Transport (ST) driver

TI_ST driver 'aka shared transport driver provides a line discipline driver, line discipline N_TI_WL value 22 to multiplex Bluetooth, FM, GPS and other short range wireless technologies interfaced over UART in WiLink connectivity chipsets.

The build for this driver is driven by the configuration option CONFIG_TI_ST and the driver sources are located at drivers/misc/ti-st/ directory.

To bind together line discipline and the protocol driver (Bluetooth, FM driver) data, TI_ST driver is probed as a platform device driver and require the platform device driver data to be initialized in the arch/XX/mach-XX.c board specific file. The platform device driver data can be populated according to latest information and documentation available at include/linux/ti_wilink_st.h for struct ti_st_plat_data{}.

struct ti_st_plat_data {
        long nshutdown_gpio;
        unsigned char dev_name[UART_DEV_NAME_LEN]; /* uart name */
        unsigned char flow_cntrl; /* flow control flag */
        unsigned long baud_rate;
        < more members in actual structure .... >


BTWILINK driver (in drivers/bluetooth/btwilink.c) provides the bluetooth connectivity. The driver makes use of the shared transport driver; which talks to the bluetooth core on the WiLink chipsets.

Build for this driver is driven by the configuration option CONFIG_BT_WILINK.

Similar to the TI ST driver, this is also a platform device driver. Hence, to be included it requires a relevant platform device registration, which can be achieved as follows:

static struct platform_device btwilink_device = {
       .name = "btwilink",
       .id = -1,

The inclusion of btwilink_device in one of the architecture specific init functions would enable the Bluetooth driver for WiLink chipsets. Include the following line in one of the architecture/platform specific init functions:


User Space components

An utility known as UIM is critical for the shared transport (TI_ST) driver to work. (Meaning, without UIM, TI_ST will not work.) Most line disciplines, if not all, require a user-space daemon to open the UART. Installing the line discipline thereby gives control to the line discipline driver.

You can obtain UIM from:;a=summary

The latest can be found at the Gingerbread branch. It's named uim-sysfs. Follow this link to get it:;a=tree;f=ti_st/uim-sysfs;h=12ce6bafd461474ad90d41a0b9523a94534e4c0a;hb=refs/heads/gingerbread

UIM needs to be run at boot since some Linux flavors may require Bluetooth or GPS to be turned on at boot.

To do so (run at boot time), have the UIM entry in one of your rc.S files. Alternatively, you can specify a special udev rule based on the platform driver in addition to the device "kim" [Need Modification].

For Android, the following entry in the init.rc should suffice: Depending on hardware platform permission for /dev/ttyxx interface to be mapped to bluetooth needs to be added in init.rc

For OMAP4:

# change permissions for Bluetooth/FM/GPS
    chmod 0600 /sys/class/rfkill/rfkill0/state
    chown bluetooth bluetooth /sys/class/rfkill/rfkill0/state
    chmod 0600 /dev/ttyO4
    chown bluetooth bluetooth /dev/ttyO1

service uim /system/bin/uim-sysfs
    user root
    group media bluetooth

Setting up the Firmware

All three connectivities -- Bluetooth, FM and GPS -- require their own firmware files. The Bluetooth firmware core file is used earlier (first) than the other cores in WiLink.

The latest firmware files are available on this site:

Shared Transport driver uses the firmware class sub-system to download firmware files. Hence the firmware ".bts" files should be placed in /system/etc/firmware/ for Android and /lib/firmware/ for Ubuntu.

On Boot Check

Since there are many versions of the drivers floating around and a lot needs to be done to get them all working fine, checking a few things as mentioned below will ensure that the porting effort went well :

Enabling Profiles on Android

Important Notes

The platform data and its structure constantly, inevitably change. Hence, before adding the platform device, make sure that the platform data matches in type and structure to the platform data defined in the file: include/linux/ti_wilink_st.h.

Support Contacts

If you have any questions, doubts or suggestions please send them to: WCG Leads.

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