10.3.1. rtl8821CS¶
RealTek（瑞昱）系列的 SDIO WiFi 设备的驱动都开发的相对比较标准，移植的难度都比较低
10.3.1.1. 添加源码¶
Luban 的 Kernel 版本为 5.10， 建议尽量获取官方的比较新的驱动（ >= 5.10).
在 source/linux-5.10/drivers/net/wireless/realtek 中创建 rtl8821CS 目录，并复制 rtl8821CS 的驱动源码
在 source/linux-5.10/drivers/net/wireless/realtek/Kconfig 中添加对 rtl8821CS 模块的索引：
source "drivers/net/wireless/realtek/rtl8821/Kconfig"
在 source/linux-5.10/drivers/net/wireless/realtek/Makefile 中添加对 rtl8821CS 模块的索引：
obj-$(CONFIG_RTL8821CS) += rtl8821CS/
10.3.1.2. Kconfig 修改¶
基于版本的差异，Luban 对 Kconfig 中 help 的字段解析可能和驱动原生的格式有差异， 在drivers/net/wireless/realtek/rtl8821/Kconfig中调整如下：
config RTL8821CS
tristate "Realtek 8821C SDIO WiFi"
- ---help---
+ help
Kconfig 修改正确后，在 make kernel_menuconfig 中应该能看到 rtl8821CS 模块， 勾选后可以进行编译错误的解决
10.3.1.3. include 目录添加¶
大部分 WiFi 驱动为了增强兼容性，驱动中会有一些存放 .h 文件的目录，而在 Makefile 中会引用这些目录，因为版本的差异， 此类目录的引用方法可能不一样
10.3.1.3.1. 出错现象¶
fatal error: drv_types.h: No such file or directory
17 | #include <drv_types.h>
10.3.1.3.2. 解决方案¶
在 source/linux-5.10/drivers/net/wireless/realtek/rtl8821cs/Makefile中修改如下：
修改引用方式，添加 srctree 前缀
添加额外的目录
-EXTRA_CFLAGS += -I$(src)/include
+EXTRA_CFLAGS += -I$(srctree)/$(src)/include
+EXTRA_CFLAGS += -I$(srctree)/$(src)/hal/phydm
+EXTRA_CFLAGS += -I$(srctree)/$(src)/hal/btc
+EXTRA_CFLAGS += -I$(srctree)/$(src)/platform
10.3.1.4. Makefile 编译优化¶
在 source/linux-5.10/drivers/net/wireless/realtek/rtl8821cs/Makefile中修改如下：
-EXTRA_CFLAGS += -O1
+EXTRA_CFLAGS += -Os
10.3.1.5. 内核配置¶
在make kernel_menuconfig进行功能配置
10.3.1.5.1. 无线配置¶
WiFi 的使用必须要在 kernel 中打开 cfg80211 和 mac80211 的支持
Networking support > Wireless
--- Wireless
<*> cfg80211 - wireless configuration API
[ ] nl80211 testmode command (NEW)
[ ] enable developer warnings (NEW)
[ ] cfg80211 certification onus (NEW)
[*] enable powersave by default (NEW)
[ ] cfg80211 DebugFS entries (NEW)
[*] support CRDA (NEW)
[*] cfg80211 wireless extensions compatibility
<*> Generic IEEE 802.11 Networking Stack (mac80211)
[*] Minstrel (NEW)
Default rate control algorithm (Minstrel) --->
[ ] Enable mac80211 mesh networking support (NEW)
[ ] Export mac80211 internals in DebugFS (NEW)
[ ] Trace all mac80211 debug messages (NEW)
[ ] Select mac80211 debugging features (NEW)
10.3.1.5.2. 蓝牙配置¶
BT 的使用必须要在 kernel 中打开bluetooth子系统相关配置
Networking support > Bluetooth subsystem support > Bluetooth device drivers
< > HCI USB driver
< > HCI SDIO driver
<*> HCI UART driver
[*] UART (H4) protocol support
< > UART Nokia H4+ protocol support
[ ] BCSP protocol support
[ ] Atheros AR300x serial support
[ ] HCILL protocol support
-*- Three-wire UART (H5) protocol support
[ ] Intel protocol support
[ ] Broadcom protocol support
[*] Realtek protocol support
[ ] Qualcomm Atheros protocol support
[ ] Intel AG6XX protocol support
[ ] Marvell protocol support
< > HCI BCM203x USB driver
< > HCI BPA10x USB driver
< > HCI BlueFRITZ! USB driver
< > HCI VHCI (Virtual HCI device) driver
< > Marvell Bluetooth driver support
< > MediaTek HCI SDIO driver
< > MediaTek HCI UART driver
10.3.1.5.3. RFKILL配置¶
rfkill的使用必须要在 kernel 中打开相关配置
Networking support > RF switch subsystem support
--- RF switch subsystem support
[ ] RF switch input support
<*> GPIO RFKILL driver
10.3.1.5.4. 驱动选择¶
要使用8821C 驱动，需要在 kernel 中打开该驱动
Device Drivers > Network device support > Wireless LAN
[*] Realtek devices
< > Realtek 8187 and 8187B USB support
< > Realtek rtlwifi family of devices ----
< > RTL8723AU/RTL8188[CR]U/RTL819[12]CU (mac80211) support
< > Realtek 802.11ac wireless chips support ----
<*> Realtek 8821C SDIO WiFi
10.3.1.6. DTS配置¶
在board.dts中进行各子节点配置
10.3.1.6.1. WIFI¶
1.打开对应的SDMC
&sdmc1 {
pinctrl-names = "default";
pinctrl-0 = <&sdmc1_pins_a>;//核对引脚是否和原理图一致
bus-width = <4>;
no-mmc;
no-sd;
non-removalbe;
cap-sdio-irq;
status = "okay";
};
2.配置控制引脚
rfkill_wlan {
compatible = "rfkill-gpio";
rfkill-name = "wlan";
rfkill-type = <1>;
reset-gpios = <&gpio_e 4 GPIO_ACTIVE_HIGH>;//模组WiFi使能引脚，根据实际原理图配置
shutdown-gpios = <&gpio_d 8 GPIO_ACTIVE_LOW>;//电源控制引脚，根据实际原理图配置
status = "okay";
};
10.3.1.6.2. BT¶
1.打开对应UART
&uart6 {
pinctrl-names = "default";
pinctrl-0 = <&uart6_pins_a>, <&uart6_rts_pins_a>, <&uart6_rts_pins_b>;//须和原理图保持一致
status = "okay";
};
2.配置控制引脚
rfkill_bt {
compatible = "rfkill-gpio";
rfkill-name = "bluetooth";
rfkill-type = <2>;
reset-gpios = <&gpio_c 6 GPIO_ACTIVE_HIGH>;//模组蓝牙使能引脚，须和原理图保持一致
status = "okay";
};
10.3.1.7. 模组配置文件¶
10.3.1.7.1. 蓝牙固件和下载工具¶
可以从模组厂获取，存放于overylay目录
├── lib
│ └── firmware
│ └── rtlbt
│ ├── rtl8821c_config//模组配置文件，最好从模组厂获取
│ └── rtl8821c_fw//模组固件，最好从模组厂获取
├── usr
│ └── bin
│ └── rtk_hciattach//模组蓝牙固件下载工具，最好从模组厂获取
10.3.1.8. 功能测试和调试¶
10.3.1.8.1. 添加相关工具包¶
在make menuconfig进行功能配置
[*] wireless tools --->
[*] bluez-utils --->
[ ] use prebuilt binary instead of building from source
[ ] build OBEX support
[ ] build CLI client
[ ] build monitor utility
[*] build tools
[*] install deprecated tools
[ ] build experimental tools
[ ] build audio plugins (a2dp and avrcp)
[ ] build health plugin
[ ] build hid plugin
[ ] build hog plugin
[ ] build mesh plugin
[ ] build midi plugin
[*] build network plugin
[ ] build nfc plugin
[ ] build sap plugin
*** sixaxis plugin needs udev /dev management ***
[ ] install test scripts
*** hid2hci tool needs udev /dev management ***
10.3.1.8.2. 测试¶
1.WiFi
insmod rtl8821.ko
ifconfig wlan0 up
iwlist wlan0 scan
2.BT
echo 0 > /sys/class/rfkill/rfkill0/state
echo 1 > /sys/class/rfkill/rfkill0/state
rtk_hciattach -n -s 115200 /dev/ttyS6 rtk_h5 &
hciconfig hci0 up
hcitool scan
10.3.1.8.3. 调试¶
核对并测试硬件信号的连通性
查看系统启动日志和模组驱动加载日志是否有异常并排查
WIFI模组驱动日志配置方法如下，Makefile中：
CONFIG_RTW_DEBUG = n//debug开关
CONFIG_RTW_LOG_LEVEL = 4//debug level