Device Driver Interface of WiLink Solution

From OMAPpedia

Latest revision as of 20:24, 20 February 2012

[edit] 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 */ \
and
        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.

[edit] 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 .... >
};

[edit] BTWILINK driver

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:

platform_device_register(&btwilink_device);

[edit] 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:

http://git.omapzoom.org/?p=platform/hardware/ti/wpan.git;a=summary

The latest can be found at the Gingerbread branch. It's named uim-sysfs. Follow this link to get it:

http://git.omapzoom.org/?p=platform/hardware/ti/wpan.git;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].

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

For OMAP4:

# change permissions for Bluetooth/FM/GPS
    chmod 0660 /sys/class/rfkill/rfkill0/state
    chown bluetooth bluetooth /sys/class/rfkill/rfkill0/state
    chmod 0660 /dev/ttyO4
    chown bluetooth bluetooth /dev/ttyO1

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

Note:

1. UIM needs access to the UART connected to BT/FM/GPS/NFC and therefore it has to be the owner/group of the UART.

2. The permission for the rfkill entry created by bluetooth kernel sub-system has to be added, which is accessed by bluedroid which belongs to group bluetooth.

[edit] 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:

https://gforge.ti.com/gf/project/wilink_drivers/

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.

[edit] 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 :

• Check up on the following default config options available in the ".config" of your kernel build directory, If any of the options among CONFIG_TI_ST, CONFIG_BT_WILINK, CONFIG_RADIO_WL128X is "=m" then it would mean the relevant driver would be built as a module. If the above mentioned options are configured to be "=y" then it would be built-in to the kernel and you would not need to perform the next 2 steps.
  
• If you intended to build the following modules: TI ST driver, btwilink driver, FM and GPS, then make sure that the following kernel object files are present in the file-system (In the root "/" for Android.): st_drv.ko, btwilink.ko, fm_drv.ko and gps_drv.ko.
  
• The above modules need to be inserted manually (with insmod) if the UIM does not do the job at boot. You can check that by doing a lising of the modules present. Use $lsmod to list the modules loaded.
  
• The directory sysfs should exist. The directory /sys/devices/platform/kim should also exist with the important entries like install, dev_name, baud_rate present. These entries should also represent at which UART the WiLink is connected for the platform.
  
• Similarily, the directory /sys/devices/platform/btwilink should exist. If this does then the hci0 interface can be checked using the command $hciconfig -a.
  
• The process uim-sysfs should be running, this can be checked by peforming the $ps command. This would be started at system boot, because of the service entry uim.
  
• The FM driver initialization can be confirmed by checking the device node (/dev/tifm or /dev/radio0 depending on the implementation).
  
• The GPS driver initialization can be confirmed by checking the device node /dev/tigps.

[edit] Enabling Profiles on Android

• GAP - Generic Access Profile:
  

  Bluetooth-Settings under Wireless Setting menu of the Setting Application in Android allows you to Scan, Pair and Connect to the devices. Upon scanning, the type of device is detected by Android and the connection is established upon the user's request.

• A2DP - Audio Streaming via Bluetooth:
  

  Android supports this profile. As soon as you have Bluetooth working, this is expected to work out of the box. On Android, apart from the baud-rate on UART no other factor should generally cause the A2DP profile to break.

• AVRCP - Audio Video Remote Control Profile:
  

  This requires the uInput to be enabled in the kernel; Issue make menuconfig for more details.

• HFP/HSP - Head Set and Hands Free (In-Call operation):
  

  While all other kind of Bluetooth data goes over UART, this one goes through the OMAP to the BT via the McBSP. Different platforms have different configurations for the McBSP that has been interfaced with BT-PCM lines. Even without the Modem, the BT-PCM lines are verified by streaming music and record voice from the BT-headset.

• HID:
  

  On connection to a Bluetooth Keyboard or Mouse, the HID functionality should work out of the box.

• PBAP/OPP:
  

  Since Android provides them, object push and Vcard listing should also work out of box.

• FTP:
  

  There are 3rd party applications, called BlueFTP, that are available from Android App Market that should work without any modifications upon installation.

• SPP:
  

  There are 3rd party applications, like BlueTerm, that are available from Android App Market that should work without any modifications upon installation.

[edit] 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.

[edit] Support Contacts

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

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