ROCKCHIP ~ Camera 闪光灯

一、闪光灯基本原理

工作模式

Camera flash led分flash和torch两种模式。

• flash：
  拍照时上光灯瞬间亮一下，电流比较大，目前是1000mA，最大电流不能超过led最大承受能力

• torch：
  只用于录video或者拿led当手电筒的情况，电流不能太大，

flash开启需要先从torch过渡，这样电流可以慢慢增大，减少冲击。

二、驱动移植

1. 硬件电路

sgm3141总体来说比较简单，只有两个引脚用于控制：FLASH_EN、FLASH/TORCH。

• FLASH_EN
  闪光灯使能引脚。

• FLASH/TORCH
  此处led flash和TORCH功能共用了同一个gpio。

“ 注意: 有的摄像头是通过pwm来控制闪光灯，具体问题具体分析，不要教条”

2. 设备树

瑞芯微sdk中没有专门针对sgm3141的驱动，网上搜了一大圈也没有搜到，很多闪光灯都是基于I2C接口，通过I2C来设置上光灯的工作模式，好在sdk中有类似的芯片rgb13h驱动，该驱动只有一个引脚用于闪光灯，和我们的功能很类似。

参考驱动文件：leds-rgb13h.c

sgm3141设备树节点

 flash_sgm3141:flash-sgm3141 {
               status = "okay";
               compatible = "sgmicro,sgm3141";
               label = "gpio-flash";
               pinctrl-names = "default";
               pinctrl-0 = <&flash_led_gpios>;
               
               led-max-microamp = <20000>;
               flash-max-microamp = <20000>;
               flash-max-timeout-us = <1000000>;
               strobe-gpios = <&gpio3 RK_PC7 GPIO_ACTIVE_HIGH>;
               enable-gpios = <&gpio3 RK_PD0 GPIO_ACTIVE_HIGH>;
               rockchip,camera-module-index = <0>;
               rockchip,camera-module-facing = "back"; 
       };

        ov13850: ov13850@10 {
         ……
            flash-leds = <&flash_sgm3141>;
         ……
        };

pinctrl设置：

&pinctrl {
       ……
       flash-led {
               flash_led_gpios: flash-led {
                       rockchip,pins =
                       /* flash led enable*/
                       <3 RK_PD0 RK_FUNC_GPIO &pcfg_pull_none>,
                       <3 RK_PC6 RK_FUNC_GPIO &pcfg_pull_none>;
               };
       };
       ……
 };

@drivers/leds/Makefile
obj-y                  += sgm3141.o

三、xml

要app支持闪光灯，还需要修改xml文件，打开该功能

@hardware/rockchip/camera/etc/camera/camera3_profiles.xml
@hardware/rockchip/camera/etc/camera/camera3_profiles_rk356x.xml

<flash.info.available value="TRUE"/>

这样，打开app就可以看到上光灯的按钮。

四、拓扑结构

拓扑结构中entity

rk3568_r:/ # media-ctl -d /dev/media0 -p
……
- entity 70: m01_f_ov5648 4-0036 (1 pad, 1 link)
             type V4L2 subdev subtype Sensor
             device node name /dev/v4l-subdev3
        pad0: Source
                [fmt:SBGGR10/2592x1944]
                -> "rockchip-csi2-dphy0":0 []

- entity 74: m00_b_ov13850 4-0010 (1 pad, 1 link)
             type V4L2 subdev subtype Sensor
             device node name /dev/v4l-subdev4
        pad0: Source
                [fmt:SBGGR10/4224x3136]
                -> "rockchip-csi2-dphy0":0 []

- entity 78: m00_b_gpio-flash (0 pad, 0 link)
             type V4L2 subdev subtype Flash
             device node name /dev/v4l-subdev5

• 摄像头：
  m00_b_ov13850、m01_f_ov5648

• 闪光灯：
  m00_b_gpio-flash，v4l2子设备/dev/v4l-subdev5

第4个字母b表示后置摄像头。

五、调试

驱动会通过sysfs创建文件节点

rk3568_r:/sys/class/leds/gpio-flash # ls
brightness  flash_strobe   max_brightness     power      trigger
device      flash_timeout  max_flash_timeout  subsystem  uevent

• 亮灭灯

亮灯
rk3568_r:/sys/class/leds/gpio-flash # echo 1 > brightness
echo 1 > brightness
灭灯
1|rk3568_r:/sys/class/leds/gpio-flash # echo 0 > brightness
echo 0 > brightness

操作对应函数调用关系

[  374.302386] Call trace:                                                                     
[  374.302428] dump_backtrace+0x0/0x178                                                        
[  374.302471] show_stack+0x14/0x20                                                            
[  374.302518] dump_stack+0x94/0xb4                                                            
[  374.302560] sgm3141_led_brightness_set+0x18/0x40                                            
[  374.302592] led_set_brightness_nopm+0x14/0x48                                               
[  374.302624] led_set_brightness+0x50/0x80                                                    
[  374.302662] brightness_store+0x74/0xc8                                                      
[  374.302691] dev_attr_store+0x18/0x28                                                        
[  374.302728] sysfs_kf_write+0x48/0x58                                                        
[  374.302759] kernfs_fop_write+0xf4/0x220                                                     
[  374.302793] __vfs_write+0x34/0x158                                                          
[  374.302810] vfs_write+0xb0/0x1d0                                                            
[  374.302828] ksys_write+0x64/0xe0                                                            
[  374.302860] __arm64_sys_write+0x14/0x20                                                     
[  374.302904] el0_svc_common.constprop.0+0x64/0x178                                           
[  374.302947] el0_svc_handler+0x28/0x78                                                       
[  374.302984] el0_svc+0x8/0xc                                                                 
[  425.607850] healthd: battery l=50 v=3 t=2.6 h=2 st=3 fc=100 chg=au                          
[  437.663757] CPU: 3 PID: 1727 Comm: sh Not tainted 4.19.232 #326                             
[  437.663869] Hardware name: Rockchip RK3568 EVB1 DDR4 V10 Board (DT)

• 闪灯

rk3568_r:/sys/class/leds/gpio-flash # echo 1 > flash_strobe
echo 1 > flash_strobe

操作对应函数调用关系

[  492.026239] Call trace:                                                                     
[  492.026291] dump_backtrace+0x0/0x178                                                        
[  492.026320] show_stack+0x14/0x20                                                            
[  492.026354] dump_stack+0x94/0xb4                                                            
[  492.026391] sgm3141_led_flash_strobe_set+0x24/0x78                                          
[  492.026453] flash_strobe_store+0x88/0xd8                                                    
[  492.026517] dev_attr_store+0x18/0x28                                                        
[  492.026571] sysfs_kf_write+0x48/0x58                                                        
[  492.026620] kernfs_fop_write+0xf4/0x220                                                     
[  492.026683] __vfs_write+0x34/0x158                                                          
[  492.026733] vfs_write+0xb0/0x1d0                                                            
[  492.026784] ksys_write+0x64/0xe0                                                            
[  492.026833] __arm64_sys_write+0x14/0x20                                                     
[  492.026867] el0_svc_common.constprop.0+0x64/0x178                                           
[  492.026912] el0_svc_handler+0x28/0x78                                                       
[  492.026966] el0_svc+0x8/0xc                                                                 
[  494.218112] CPU: 2 PID: 1727 Comm: sh Not tainted 4.19.232 #326                             
[  494.218218] Hardware name: Rockchip RK3568 EVB1 DDR4 V10 Board (DT)  

“ 为方便查看驱动回调函数调用顺序，可以在下面3个回调函数入口增加dump_stack()， sgm3141_led_brightness_set() sgm3141_led_flash_strobe_set() sgm3141_set_ctrl()
”

六、app 测试驱动 log分析

1. 上电加载驱动log

rk3568_r:/ # dmesg | grep sgm3141
dmesg | grep sgm3141
[    0.853883] sgm3141-flash flash-sgm3141: driver version: 00.01.01
[    0.853956] sgm3141-flash flash-sgm3141: Unable to get pwm device

2. 打开摄像头

打开摄像头功能，app调用ioctl命令如下：

V4L2_CID_FLASH_LED_MODE ：app 设置led mode为 V4L2_FLASH_LED_MODE_FLASH(1)
V4L2_CID_FLASH_TIMEOUT ：设置超时时间
V4L2_CID_FLASH_STROBE_STOP ：停止闪光

[   36.213220] sgm3141 V4L2_CID_FLASH_LED_MODE 1
[   36.213250] sgm3141_set_ctrl(),376
[   36.213256] sgm3141_set_output(),78 0
[   36.213265] sgm3141_led_flash_strobe_set(),166 state=1
[   36.213281] sgm3141_set_output(),78 1

[   36.213298] sgm3141 V4L2_CID_FLASH_TIMEOUT
[   36.213300] sgm3141_set_ctrl(),412
[   36.213308] sgm3141_led_flash_timeout_set(),195 timeout=500000


[   36.213318] sgm3141 V4L2_CID_FLASH_STROBE_STOP 1
[   36.213323] sgm3141_set_ctrl(),406
[   36.213327] sgm3141_led_flash_strobe_set(),166 state=0
[   36.213332] sgm3141_set_output(),78 0
[   36.213461] sgm3141_timeout_work(),117

3. 拍照

拍照功能，app调用ioctl命令如下：

V4L2_CID_FLASH_LED_MODE ：设置led mod为 V4L2_FLASH_LED_MODE_TORCH(2),并点灯
V4L2_CID_FLASH_LED_MODE：到达指定超时时间（2.7秒），设置led mod为 V4L2_FLASH_LED_MODE_NONE 0
V4L2_CID_FLASH_LED_MODE：在此设置led mod为V4L2_FLASH_LED_MODE_FLASH(1)
V4L2_CID_FLASH_STROBE_STOP:停止闪光

[   90.246203] sgm3141 V4L2_CID_FLASH_LED_MODE 2
[   90.246251] sgm3141_set_ctrl(),376
[   90.246262] sgm3141_set_output(),78 0
[   90.246277] sgm3141_set_output(),78 1

[   92.902746] sgm3141 V4L2_CID_FLASH_LED_MODE 0
[   92.902775] sgm3141_set_ctrl(),376
[   92.902781] sgm3141_set_output(),78 0

[   93.034903] sgm3141 V4L2_CID_FLASH_LED_MODE 1
[   93.034929] sgm3141_set_ctrl(),376
[   93.034934] sgm3141_set_output(),78 0
[   93.034943] sgm3141_led_flash_strobe_set(),166 state=1
[   93.034959] sgm3141_set_output(),78 1

[   93.034977] sgm3141 V4L2_CID_FLASH_STROBE_STOP 1
[   93.034988] sgm3141_set_ctrl(),406
[   93.034993] sgm3141_led_flash_strobe_set(),166 state=0
[   93.035002] sgm3141_set_output(),78 0
[   93.035058] sgm3141_timeout_work(),117

从log可以看出，app拍照的时候，闪光灯操作是通过v4l2下发的命令，

而我们直接操作宏dev_attr_store创建的文件节点则是通过在sysfs文件节点（brightness flash_strobe）直接调用到操作函数。

4. 退出摄像头

[  317.882459] sgm3141 V4L2_CID_FLASH_LED_MODE 0
[  317.882522] sgm3141_set_ctrl(),376
[  317.882532] sgm3141_set_output(),78 0

七、驱动获取

一口君修改过的驱动已经上传到gitee，获取地址：
https://gitee.com/yikoulinux/sgm3141