高通linux-总线介绍

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1. i2c
   1. 概述

驱动：

drivers/i2c/

高通平台的i2c:

drivers/i2c/busses/i2c-msm-v2.c

 

1. 1. 1. 分析

本产品用到i2c的地方有：camera。

以camera的i2c为例：

设备树内容内容：

1. 
   i2c_3: i2c@78b7000 {
2. compatible = "qcom,i2c-msm-v2";
3. #address-cells = <1>;
4. #size-cells = <0>;
5. reg-names = "qup_phys_addr";
6. reg = <0x78b7000 0x1000>;
7. interrupt-names = "qup_irq";
8. interrupts = <0 97 0>;
9. clocks = <&clock_gcc 0x8caa5b4f>,
10. <&clock_gcc 0x9e25ac82>;
11. clock-names = "iface_clk", "core_clk";
12. qcom,clk-freq-out = <100000>;
13. qcom,clk-freq-in = <19200000>;
14. pinctrl-names = "i2c_active", "i2c_sleep";
15. pinctrl-0 = <&i2c_3_active>;
16. pinctrl-1 = <&i2c_3_sleep>;
17. qcom,noise-rjct-scl = <0>;
18. qcom,noise-rjct-sda = <0>;
19. dmas = <&dma_blsp1 8 64 0x20000020 0x20>,
20. <&dma_blsp1 9 32 0x20000020 0x20>;
21. dma-names = "tx", "rx";
22. qcom,master-id = <86>;
23. };

 

根据内核配置文件和compatible = "qcom,i2c-msm-v2"; 很容易找到概述

drivers/i2c/busses/i2c-msm-v2.c。

 

摘取i2c-msm-v2.c中关键内容：

1. 
   static struct of_device_id i2c_msm_dt_match[] = {
2.        {
3.               .compatible = "qcom,i2c-msm-v2",
4.        },
5.        {}
6. };
7.  
8. static struct platform_driver i2c_msm_driver = {
9.        .probe  = i2c_msm_probe,
10.        .remove = i2c_msm_remove,
11.        .driver = {
12.               .name           = "i2c-msm-v2",
13.               .owner          = THIS_MODULE,
14.               .pm             = &i2c_msm_pm_ops,
15.               .of_match_table = i2c_msm_dt_match,
16.        },
17. };
18.  
19. static int i2c_msm_init(void)
20. {
21.        return platform_driver_register(&i2c_msm_driver);
22. }

 

结合linux i2c设备驱动原理，熟悉上面出现的函数。

 

以下函数，可对应到设备树内容中很多信息：

1. 
   /*
2.  * i2c_msm_rsrcs_process_dt: copy data from DT to platform data
3.  * @return zero on success or negative error code
4.  */
5. static int i2c_msm_rsrcs_process_dt(struct i2c_msm_ctrl *ctrl,
6.                            struct platform_device *pdev)
7. {
8.    u32 fs_clk_div, ht_clk_div, noise_rjct_scl, noise_rjct_sda;
9.    int ret;
10.    struct i2c_msm_dt_to_pdata_map map[] = {
11.    {"i2c",                        &pdev->id,    DT_REQ,  DT_ID,  -1},
12.    {"qcom,clk-freq-out",          &ctrl->rsrcs.clk_freq_out,
13.                                          DT_REQ,  DT_U32,  0},
14.    {"qcom,clk-freq-in",           &ctrl->rsrcs.clk_freq_in,
15.                                          DT_REQ,  DT_U32,  0},
16.    {"qcom,disable-dma",           &(ctrl->rsrcs.disable_dma),
17.                                          DT_OPT,  DT_BOOL, 0},
18.    {"qcom,master-id",             &(ctrl->rsrcs.clk_path_vote.mstr_id),
19.                                          DT_SGST, DT_U32,  0},
20.    {"qcom,noise-rjct-scl",        &noise_rjct_scl,
21.                                          DT_OPT,  DT_U32,  0},
22.    {"qcom,noise-rjct-sda",        &noise_rjct_sda,
23.                                          DT_OPT,  DT_U32,  0},
24.    {"qcom,high-time-clk-div",     &ht_clk_div,
25.                                          DT_OPT,  DT_U32,  0},
26.    {"qcom,fs-clk-div",            &fs_clk_div,
27.                                          DT_OPT,  DT_U32,  0},
28.    {NULL,  NULL,                                0,       0,       0},
29.    };
30.    ret = i2c_msm_dt_to_pdata_populate(ctrl, pdev, map);
31.    if (ret)
32.        return ret;
33.    /* set divider and noise reject values */
34.    return i2c_msm_set_mstr_clk_ctl(ctrl, fs_clk_div, ht_clk_div,
35.                                   noise_rjct_scl, noise_rjct_sda);
36. }

 

输入输出时钟设置：

  qcom,clk-freq-out = <100000>;

  qcom,clk-freq-in = <19200000>;

 

 

1. 1.  i2c、spi、usb驱动架构的类比

这几个设备用的架构是linux常用架构之一。从板级逻辑层看，usb具有总线热拔插能力，这层对于usb设备已无意义；假如usb设备有这层代码，说明板子上有这个设备，但实际并没有usb设备，反而带来了错误。熟悉类比图中出现的函数名。