MTK8766 LK GPIO初始化状态设置分析

问题来源是M.2 Dongle的LED灯在kernel起来之前就亮了，kernel起来之后又初始化成熄灭状态。通过排查硬件规格书、GPIO表格，大概判定是前期软件初始化不正确造成的。通过观察串口打印的log，发现灯开始亮起来的瞬间是运行在lk中。

找到MTK 的LK代码路径

 MT8766_A11_AP/vendor/mediatek/proprietary/bootable/bootloader/lk/

找到MTK的LK代码编译out目录

 MT8766_A11_AP/out/target/product/tb8766p1_bsp_1g/obj/LK_OBJ/build-tb8766p1_bsp_1g/

再从out目录下的plarform目录确定当前编译的平台是mt6761，从而在对应的gpio配置输出函数中添加log

 MT8766_A11_AP/vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6761/mt_gpio.c
 ​
 S32 mt_set_gpio_mode_chip(u32 pin, u32 mode)
 {
 ......
 添加以下代码对改GPIO进行debug
 ​
     if (pin == 174)
     {
         GPIOVER("============ fuck gpio ===============\n");
         mdelay(1000);
     }
 ​
     return RSUCCESS;
 }

通过log大概确定相关动作是在lk_dtb_init()中或者后面一点点

 [254] [SBC] image dtbo auth init pass
 [254] [SBC] image dtbo cert vfy pass(22 ms)
 [255] [PROFILE] mmc read 1 blks in 0 ms: 8KB/s
 [256] dtbo_total_len: 0x8a17
 [257] [PROFILE] mmc read 69 blks in 1 ms: 34500KB/s
 [258] [PROFILE] mmc read 1 blks in 0 ms: 8KB/s
 [259] [SBC][oem] img auth pass
 [259] [SBC] dtbo vfy pass(1 ms)
 [260] dtbo_offset: 0x40
 [260] [PROFILE] ::: lvl(3) load_dtbo_buffer takes 30 ms
 [261] dtbo_size : 35287
 [272] [PROFILE] ::: lvl(3) dtb_overlay takes 11 ms
 [273] [PROFILE] ::: lvl(2) lk_dtb_init takes 100 ms
 [275] [GPIO] mt_set_gpio_mode_chip: ============ fuck gpio ===============
 [1278] [PROFILE] mmc read 32 blks in 2 ms: 8000KB/s
 [1279] [LK_ENV]ENV of area 0 initialize sucess
 [1280] [PROFILE] mmc read 32 blks in 1 ms: 16000KB/s
 [1280] [LK_ENV]ENV SIG of area 1 is wrong
 [1281] [LK_ENV]env area: 0
 [1281] [LK_ENV]env:
 [1281] [LK_ENV]md1_ccb_cap_gear=1
 [1282] [LK_ENV]md1_ccb_gear_list=1(2,20);2(2,10);3(0,0);11(2,2);12(2,62)
 [1283] [LK_ENV]env area: 1
 [1283] [LK_ENV]no valid env
 [1283] [PROFILE] ::: lvl(2) ENV init takes 7 ms
 [1284] mblock_reserve-R start: 0x7f040000, sz: 0xdb0000 map:0 name:framebuffer

最终定位到以下调用关系

 platform_early_init();
     |
     mt_gpio_set_default();
         |
         mt_gpio_set_default_chip();

观察mt_gpio_set_default，发现相关配置参数是从设备树中获取的，展开mt_gpio_set_default()函数中的mt_gpio_get_default_chip_from_dtb()调用，发现相关设备树节点名字是gpio@10005000，相关属性的名字是gpio_init_default。用adb pull /sys/firmware/fdt，反编译设备树确认存在这个属性和节点。

在kernel中过滤文本搜索gpio_init_default属性，发现并不存在与当前硬件相关的设备树文件！那么，猜测该属性应该是从别的设备树文件中合并进来的。再在代码中使用grep -nr gpio_init_default全局过滤搜索，发现有以下文件与之相关。

 ./kernel-4.19/arch/arm64/boot/dts/mediatek/mt6779-evb.dts:604:  gpio_init_default = <0 0 0 0 1 1 1>,
 ./vendor/mediatek/proprietary/tools/dct/python/obj/GpioObj.py:746:        gen_str += '''\tgpio_init_default = '''
 ./vendor/mediatek/proprietary/tools/dct/python/obj/GpioObj.py:772:        gen_str += '''\tgpio_init_default = '''
 ./vendor/mediatek/proprietary/bootable/bootloader/preloader/tools/dct/obj/GpioObj.py:710:        gen_str += '''\tgpio_init_default = '''
 ./vendor/mediatek/proprietary/bootable/bootloader/preloader/tools/dct/obj/GpioObj.py:736:        gen_str += '''\tgpio_init_default = '''
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6768/gpio_init.c:79:#define GPIO_DT_NODE_PROP_NAME  "gpio_init_default"
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6765/mt_gpio_init.c:134:#define GPIO_DT_NODE_PROP_NAME  "gpio_init_default"
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6761/mt_gpio_init.c:134:#define GPIO_DT_NODE_PROP_NAME  "gpio_init_default"
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6785/gpio_init.c:79:#define GPIO_DT_NODE_PROP_NAME  "gpio_init_default"
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6771/gpio_init.c:76:#define GPIO_DT_NODE_PROP_NAME  "gpio_init_default"
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/scripts/dct/obj/GpioObj.py:710:        gen_str += '''\tgpio_init_default = '''
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/scripts/dct/obj/GpioObj.py:736:        gen_str += '''\tgpio_init_default = '''

打开与之相关的文件

 vendor/mediatek/proprietary/bootable/bootloader/lk/scripts/dct/obj/GpioObj.py

发现相关的python调用方法是fill_init_default_dtsiFile，那么再全局过滤搜索这个方法名，发现有以下文件与之相关。

 ./vendor/mediatek/proprietary/tools/dct/python/obj/ChipObj.py:260:                gen_str += gpioObj.fill_init_default_dtsiFile()
 ./vendor/mediatek/proprietary/tools/dct/python/obj/GpioObj.py:649:    def fill_init_default_dtsiFile(self):
 ./vendor/mediatek/proprietary/tools/dct/python/obj/GpioObj.py:744:    def fill_init_default_dtsiFile(self):
 ./vendor/mediatek/proprietary/tools/dct/python/obj/GpioObj.py:770:    def fill_init_default_dtsiFile(self):
 ./vendor/mediatek/proprietary/bootable/bootloader/preloader/tools/dct/obj/ChipObj.py:224:                gen_str += gpioObj.fill_init_default_dtsiFile()
 ./vendor/mediatek/proprietary/bootable/bootloader/preloader/tools/dct/obj/GpioObj.py:613:    def fill_init_default_dtsiFile(self):
 ./vendor/mediatek/proprietary/bootable/bootloader/preloader/tools/dct/obj/GpioObj.py:708:    def fill_init_default_dtsiFile(self):
 ./vendor/mediatek/proprietary/bootable/bootloader/preloader/tools/dct/obj/GpioObj.py:734:    def fill_init_default_dtsiFile(self):
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/scripts/dct/obj/ChipObj.py:207:                gen_str += gpioObj.fill_init_default_dtsiFile()
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/scripts/dct/obj/GpioObj.py:613:    def fill_init_default_dtsiFile(self):
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/scripts/dct/obj/GpioObj.py:708:    def fill_init_default_dtsiFile(self):
 ./vendor/mediatek/proprietary/bootable/bootloader/lk/scripts/dct/obj/GpioObj.py:734:    def fill_init_default_dtsiFile(self):

打开与之相关的文件

 vendor/mediatek/proprietary/bootable/bootloader/lk/scripts/dct/obj/ChipObj.py

内容如下：

     def gen_custDtsi(self):
         log(LogLevel.info, 'Start to generate cust_dtsi file...')
         fp = open(os.path.join(ModuleObj.get_genPath(), 'cust.dtsi'), 'w')
         gen_str = ModuleObj.writeComment()
 ​
         # if early porting, gen empty dtsi file for kernel
         if self.__epFlag:
             fp.write(gen_str)
             fp.close()
             return
 ​
         #sorted_list = sorted(self.__objs.keys())
         #for tag in sorted_list:
         for tag in self.__objs.keys():
             if cmp(tag, 'gpio') == 0:
                 gpioObj = self.create_obj(tag)
                 gen_str += ModuleObj.writeHeader(gpioObj.get_dtsiFileName())
                 gen_str += gpioObj.fill_mapping_dtsiFile()
                 gen_str += gpioObj.fill_init_default_dtsiFile()
             else:
                 obj = self.create_obj(tag)
                 gen_str += ModuleObj.writeHeader(obj.get_dtsiFileName())
                 gen_str += obj.fill_dtsiFile()
 ​
             gen_str += '''\n\n'''
 ​
         fp.write(gen_str)
         fp.close()
         log(LogLevel.info, 'Generate cust_dtsi file successfully!')

可以从中判断出最终生成了cust.dtsi，全局搜索这个文件find -name cust.dtsi，发现生成路径是

 ./out/target/product/tb8766p1_bsp_1g/obj/KERNEL_OBJ/arch/arm/boot/dts/tb8766p1_bsp_1g/cust.dtsi

打开后确认生成的文件存在gpio@10005000节点和gpio_init_default属性。但是目前又不能判断到底是从哪个文件中解析了配置，从而生成了最终的设备树文件。好在该方法中打印了log，再从Android的编译log中搜索Start to generate cust_dtsi file...，发现以下内容：

 [ 60% 688/1130] build out/target/product/tb8766p1_bsp_1g/obj/FAKE/treble_sepolicy_tests_27.0_intermediates/27.0_mapping.combined.cil
 [ 60% 689/1130] build out/target/product/tb8766p1_bsp_1g/obj/KERNEL_OBJ/arch/arm/boot/dts/tb8766p1_bsp_1g/cust.dtsi
 [DCT_INFO]: DWS file path is /home/123/workspace/MT8766_A11_AP/kernel-4.19/drivers/misc/mediatek/dws/mt6761/tb8766p1_bsp_1g.dws
 [DCT_INFO]: Gen files path is /home/123/workspace/MT8766_A11_AP/out/target/product/tb8766p1_bsp_1g/obj/KERNEL_OBJ/arch/arm/boot/dts/tb8766p1_bsp_1g
 [DCT_INFO]: Log files path is /home/123/workspace/MT8766_A11_AP/out/target/product/tb8766p1_bsp_1g/obj/KERNEL_OBJ/arch/arm/boot/dts/tb8766p1_bsp_1g
 [DCT_INFO]: Parameter is cust_dtsi
 [DCT_INFO]: chip id: MT6761
 [DCT_INFO]: Chip ID : MT6761
 [DCT_INFO]: Project Info: Merlot_Phone
 [DCT_INFO]: Start to generate cust_dtsi file...
 [DCT_INFO]: Generate cust_dtsi file successfully!
 [ 61% 690/1130] //system/core/init:libinit static link libinit.a
 [ 61% 691/1130] //system/core/init:libinit static link libinit.a

好家伙，绕了一圈原来是tb8766p1_bsp_1g.dws！

那么修改dws 的GPIO配置，重新编译。。。发现cust.dtsi中对应的GPIO配置变了，烧录验证。。。成功！