Porting a Realtek Wi-Fi driver to Rockchip: RTL8723CS

This article covers the technical body of bilingual source RK-SM-YF-210 V1.0. It uses RTL8723CS and Rockchip BSP kernel interfaces. The source does not specify a kernel version; its WIFI_HAL requirement applies to Android 8.0 and later. For ArmSoM this is a platform reference: check the actual wireless module, SoC, BSP and kernel interfaces. No hardware validation was performed. Figures come from the single bilingual PDF, including Chinese UI; no separate English figures exist.

1 Purpose

Help developers port a Realtek Wi-Fi driver to Rockchip. The example below is rtl8723cs.

2 Driver changes

2.1 Add the driver to the kernel

The common directory is drivers/net/wireless/rockchip_wlan/. Add to its Makefile:

obj-$(CONFIG_RTL8723CS) += rtl8723cs/

Add to Kconfig in the same directory:

source "drivers/net/wireless/rockchip_wlan/rtl8723cs/Kconfig"

Rename the driver package to rtl8723cs and place it in drivers/net/wireless/rockchip_wlan/rtl8723cs.

2.2 Modify the driver Makefile

The Realtek driver defaults to PC. Switch to Rockchip: change CONFIG_PLATFORM_I386_PC = y to n, and CONFIG_PLATFORM_ARM_RK3188 = n to y. Rockchip uses a .ko driver; change its module name to 8723cs.

ifeq ($(CONFIG_PLATFORM_ARM_RK3188), y)
EXTRA_CFLAGS+= -DCONFIG_LITTLE_ENDIAN -DCONFIG_PLATFORM_ANDROID -DCONFIG_PLATFORM_ROCKCHIPS
……
#EXTRA_CFLAGS += -DRTW_ENABLE_WIFI_CONTROL_FUNC //注意这个要注释掉 Need to comment this out
……
MODULE_NAME := 8723cs
Endif

The source excerpt contains ellipses and ends with Endif, retained here. Check the actual GNU Make closing keyword, lowercase endif. Comment out the RTW_ENABLE_WIFI_CONTROL_FUNC line. For Android 8.0 and later also change CONFIG_RTW_WIFI_HAL = n to CONFIG_RTW_WIFI_HAL = y.

2.3 Modify entry functions

The common Realtek entry is rtw_drv_entry: USB uses os_dep/linux/usb_intf.c, SDIO uses os_dep/linux/sdio_intf.c, and PCIe uses os_dep/linux/pci_intf.c.

1. Change static int __init rtw_drv_entry(void) to static int rtw_drv_entry(void).
2. Change static void __exit rtw_drv_halt(void) to static void rtw_drv_halt(void).
3. Comment out module_init(rtw_drv_entry); and module_exit(rtw_drv_halt);.
4. Add the Rockchip entry wrappers.

Entry functions before modification (bilingual source)

Entry wrappers after modification (log lines are already clipped at the right in the source)

The following transcribes visible code. Two log lines containing DRIVERVERSION are clipped by the original image; comments identify them without inventing missing characters. Original function bodies are collapsed in the screenshot, so this is not a complete source file.

#include <linux/rfkill-wlan.h>
extern int get_wifi_chip_type(void);
extern int rockchip_wifi_power(int on);
extern int rockchip_wifi_set_carddetect(int val);

int rockchip_wifi_init_module_rtkwifi(void)
{
#ifdef CONFIG_WIFI_LOAD_DRIVER_WHEN_KERNEL_BOOTUP
    int type = get_wifi_chip_type();
    if (type < WIFI_AP6XXX_SERIES || type == WIFI_ESP8089) return 0;
#endif
    printk("\n");
    printk("=======================================================\n");
    printk("==== Launching Wi-Fi driver! (Powered by Rockchip) ====\n");
    printk("=======================================================\n");
    /* Source log line clipped after DRIVERVERSION; see original figure. */
    rockchip_wifi_power(1);
    rockchip_wifi_set_carddetect(1);
    return rtw_drv_entry();
}

void rockchip_wifi_exit_module_rtkwifi(void)
{
#ifdef CONFIG_WIFI_LOAD_DRIVER_WHEN_KERNEL_BOOTUP
    int type = get_wifi_chip_type();
    if (type < WIFI_AP6XXX_SERIES || type == WIFI_ESP8089) return;
#endif
    printk("\n");
    printk("=======================================================\n");
    printk("==== Dislaunching Wi-Fi driver! (Powered by Rockchip) ====\n");
    printk("=======================================================\n");
    /* Source log line clipped after DRIVERVERSION; see original figure. */
    rtw_drv_halt();
    rockchip_wifi_set_carddetect(0);
    rockchip_wifi_power(0);
}
#ifdef CONFIG_WIFI_BUILD_MODULE
module_init(rockchip_wifi_init_module_rtkwifi);
module_exit(rockchip_wifi_exit_module_rtkwifi);
#else
#ifdef CONFIG_WIFI_LOAD_DRIVER_WHEN_KERNEL_BOOTUP
late_initcall(rockchip_wifi_init_module_rtkwifi);
module_exit(rockchip_wifi_exit_module_rtkwifi);
#else
EXPORT_SYMBOL(rockchip_wifi_init_module_rtkwifi);
EXPORT_SYMBOL(rockchip_wifi_exit_module_rtkwifi);
#endif
#endif
//module_init(rtw_drv_entry);
//module_exit(rtw_drv_halt);

2.4 Rockchip MAC address support (optional)

If required by the project, modify rtl8723cs/core/rtw_ieee80211.c: add #include <linux/rfkill-wlan.h> and support for rockchip_wifi_mac_addr(mac) in void rtw_macaddr_cfg(u8 *out, const u8 *hw_mac_addr).

MAC address changes

/* Use the mac address stored in the Efuse */
if (hw_mac_addr) {
    _rtw_memcpy(mac, hw_mac_addr, ETH_ALEN);
}
if (!rockchip_wifi_mac_addr(mac)) {
    printk("Get mac address from flash:[%02x:%02x:%02x:%02x:%02x:%02x]\n", mac[0], mac[1],
        mac[2], mac[3], mac[4], mac[5]);
}

2.5 WOWLAN support (optional)

As required by the project, change both CONFIG_WOWLAN = n and CONFIG_GPIO_WAKEUP = n to y in the driver Makefile. Add rockchip_wifi_get_oob_irq() support in platform/platform_ops.c:

Wake interrupt changes

#include <linux/rfkill-wlan.h>
extern unsigned int oob_irq;
int platform_wifi_power_on(void)
{
    int ret = 0;
    oob_irq = rockchip_wifi_get_oob_irq();
    return ret;
}

Reference

Official ArmSoM documentation; source RK-SM-YF-210 V1.0, PDF pages 5–10.