一、I2C配置

1.根据原理图，查找相关的i2c引脚对应的GPIO值，以GPIO10作为I2C_SDA,GPIO11作为I2C_SCL为例。

2.根据MSM8937 DEVICE SPECIFICATION文档，查找GPIO10与GPIO11对应的BLSP,以及检查GPIO10与GPIO11是否可以作为I2C来使用。根据文档,GPIO10对应BLSP3_1,GPIO11对应BLSP3_0。

3.根据80-nu767-1_h_linux_bam_low-speed_peripherals_configuration_and_debug_guide文件，查找I2C部分BLSP3_0与BLSP3_1对应内容，包括其物理地址、reg size、中断号......

4.进入kernel/msm-3.18/arch/arm/boot/dts/qcom/路径下修改msm8937-pinctrl.dtsi文件

GPIO配置如下：

i2c_3 {

i2c_3_active: i2c_3_active {

/* active state */

mux {

pins = "gpio10", "gpio11";

function = "blsp_i2c3";

};

config {

pins = "gpio10", "gpio11";

drive-strength = <2>;

bias-disable;

};

};

i2c_3_sleep: i2c_3_sleep {

/* suspended state */

mux {

pins = "gpio10", "gpio11";

function = "gpio";

};

config {

pins = "gpio10", "gpio11";

drive-strength = <2>;

bias-disable;

};

};

};

5.进入kernel/msm-3.18/arch/arm/boot/dts/qcom/路径下修改msm8937.dtsi文件

添加一个新的设备树节点

（1）添加i2c_3

aliases {

smd1 = &smdtty_apps_fm;

smd2 = &smdtty_apps_riva_bt_acl;

smd3 = &smdtty_apps_riva_bt_cmd;

smd4 = &smdtty_mbalbridge;

smd5 = &smdtty_apps_riva_ant_cmd;

smd6 = &smdtty_apps_riva_ant_data;

smd7 = &smdtty_data1;

smd8 = &smdtty_data4;

smd11 = &smdtty_data11;

smd21 = &smdtty_data21;

smd36 = &smdtty_loopback;

spi3 = &spi_3;

i2c2 = &i2c_2;

i2c5 = &i2c_5;

i2c3 = &i2c_3;

sdhc1 = &sdhc_1; /* SDC1 eMMC slot */

sdhc2 = &sdhc_2; /* SDC2 for SD card */

};

（2）配置i2c_3

i2c_3: i2c@78b7000 { /* BLSP1 QUP3 */

compatible = "qcom,i2c-msm-v2";

#address-cells = <1>;

#size-cells = <0>;

reg-names = "qup_phys_addr";

reg = <0x78b7000 0x600>;

interrupt-names = "qup_irq";

interrupts = <0 97 0>;

qcom,clk-freq-out = <400000>;

qcom,clk-freq-in = <19200000>;

clock-names = "iface_clk", "core_clk";

clocks = ,

;

pinctrl-names = "i2c_active", "i2c_sleep";

pinctrl-0 = ;

pinctrl-1 = ;

qcom,noise-rjct-scl = <0>;

qcom,noise-rjct-sda = <0>;

qcom,master-id = <86>;

dmas = ,

;

dma-names = "tx", "rx";

status = "okey";

};

6.进入kernel/msm-3.18/drivers/clk/msm路径下修改clock-gcc-8952.c文件

添加时钟节点如下图所示：

static struct rcg_clk blsp1_qup1_i2c_apps_clk_src = {

.cmd_rcgr_reg = BLSP1_QUP1_I2C_APPS_CMD_RCGR,

.set_rate = set_rate_hid,

.freq_tbl = ftbl_gcc_blsp1_2_qup1_4_i2c_apps_clk,

.current_freq = &rcg_dummy_freq,

.base = &virt_bases[GCC_BASE],

.c = {

.dbg_name = "blsp1_qup1_i2c_apps_clk_src",

.ops = &clk_ops_rcg,

VDD_DIG_FMAX_MAP1(LOWER, 50000000),

CLK_INIT(blsp1_qup1_i2c_apps_clk_src.c),

},

};

二、I2C BUS验证

配置好I2C后，我们需保证I2C BUS被注册

验证过程如下：

adb shell //-------> Get adb shell

cd /dev/

ls i2c* //--------> to list all the i2c buses

如果显示i2c-3，则表示I2C BUS已被注册

三、I2C调试检查

1、检查I2C配置的相关内容，是否存在错误，或者漏配。

2、确保SDA和SCL所配置的GPIO没有被配置，否则会硬件配置出问题或者GPIO设置无效。

3、若I2C配置无误后，检查相关硬件问题

使用万用表测量I2C_SDA以及I2C_SCL的供电电压，如果与原理图中所示供电电压相差无几，则表示I2C供电电压没有问题。反之，则代表供电电压存在问题。

4、添加从设备

（1）、 通过设备树来注册一个从设备

如果I2C总线正常工作，我们就可以创建一个从设备驱动程序并注册到i2c总线上

我们使用st1663i触摸屏的驱动注册作为范例，引用文件：

kernel/drivers/input/touchscreen/st1663i/sitronix_i2c_touch.c.c

（2）、创建一个设备树节点

文件修改：

/kernel/arch/arm/boot/dts/qcom/msm8917-pmi8937-qrd-sku5.dtsi

添加一个新的设备树节点：

i2c@78b7000 {

status = "ok";

st1663i@70 {

compatible = "sitronix-tp";

reg = <0x70>;

interrupt-parent = ;

interrupts = <65 0x00>;

reset-gpio = ;

irq-gpio = ;

/*avdd-supply = ;*/

vdd-supply = ;

vcc_i2c-supply = ;

/* pins used by touchscreen */

pinctrl-names = "pmx_ts_active",

"pmx_ts_suspend",

"pmx_ts_release";

pinctrl-0 = ;

pinctrl-1 = ;

pinctrl-2 = ;

st1663i,i2c-pull-up;

st1663i,no-force-update;

st1663i,num_max_touches = <10>;

st1663i,panel-coords = <0 0 480 800>;

st1663i,display-coords = <0 0 480 800>;

st1663i,button-map= <139 172 158>;

st1663i,have-touch-key;

st1663i,driver-send-cfg;

};

};

（3）、编译完成后，利用示波器测量I2C_SDA以及I2C_SCL波形

测试流程如下

adb root

adb remount

adb push i2c_test system/bin

adb shell

cd system/bin

chmod 777 i2c_test

./i2c_test /dev/i2c-3 0xaddr（从设备物理地址） 0（读） 0xaddr(寄存器地址)

如果I2C没有问题，所示I2C_SDA波形应为以下形式

I2C start > 0xE0 (write of 0x70) > 0x1 (reg offset ) > I2C stop > delay > I2C