Platform: RK3399
OS: Android 7.1
Kernel: v4.4.83

用的是SDIO介面的AP6356S。
此文主要記錄下除錯的過程和方法。

原因：

硬體電源上有個0歐姆電阻沒焊。

除錯：

檢查DTS配置有沒有出錯：

sdio_pwrseq: sdio-pwrseq {
    compatible = "mmc-pwrseq-simple";
    clocks = <&rk818 1>;
    clock-names = "ext_clock";
    pinctrl-names = "default"
 
;
    pinctrl-0 = <&wifi_enable_h>;
    //控制WiFi電源的GPIO
    reset-gpios = <&gpio0 10 GPIO_ACTIVE_LOW>; /* GPIO0_B2 */
};

wireless-wlan {
    compatible = "wlan-platdata";
    rockchip,grf = <&grf>;
    wifi_chip_type = "ap6354";
    sdio_vref = <1800>;
    //控制WiFi中斷的GPIO
    WIFI,host_wake_irq =
 
 <&gpio0 3 GPIO_ACTIVE_HIGH>; /* GPIO0_a3 */
    status = "okay";
};

SDIO WiFi註冊成功會有如下Log:

mmc2: new ultra high speed SDR104 SDIO card at address 0001 

檢視sys/bus/sdio/devices也能看到裝置，如果沒有說明硬體有異常。

檢查硬體：
命令做SDIO導通性測試，萬用表量測拉低拉高是否可控。

GPIO2_C4/SDIO0_D0/SPI5_RXD
GPIO2_C5/SDIO0_D1/SPI5_TXD
GPIO2_C6/SDIO0_D2/SPI5_CLK
GPIO2_C7/SDIO0_D3/SPI5_CS
GPIO2_D0/SDIO0_CMD_u
GPIO2_D1/SDIO0_CLKOUT/TEST_CLKOUT1


GRF base  0xFF770000
 

GRF_GPIO2C_IOMUX 0x0e008
GRF_GPIO2D_IOMUX 0x0e00c


io -4 -r 0xff77e008     //bit[15]~bit[8] //5500
io -4 -r 0xff77e00C     //bit[0]~bit[3] //5
rk3399_mid:/ # io -4 0xff77e008 
ff77e008: 00005555
rk3399_mid:/ # io -4 0xff77e00C
ff77e00c: 00000005

導通性測試
配製為GPIO
io -4 -w 0xFF77e008 0x0fff0000
io -4 -w 0xFF770e00c 0x000f0000

配製為輸出FF78_0000
io -4 -w 0xFF780004 0x03f00000

配製為高電平
io -4 -w 0xFF780000 0x03f00000

配製為低電平
io -4 -w 0xFF780000 0x00000000


GPIO2_C4/SDIO0_D0/SPI5_RXD


GPIO0_B2(WIFI_REG_ON)

io -4 -w 0xFF720004 0x04000400
io -4 -w 0xFF720000 0x04000400

io -4 -w 0xFF720004 0x00000000
io -4 -w 0xFF720000 0x00000000


echo 1084 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio1084/direction

echo 1085 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio1085/direction

echo 1086 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio1086/direction

echo 1087 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio1087/direction

echo 1088 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio1088/direction

echo 1089 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio1089/direction

echo 1 > /sys/class/gpio/gpio1084/value
echo 1 > /sys/class/gpio/gpio1085/value
echo 1 > /sys/class/gpio/gpio1086/value
echo 1 > /sys/class/gpio/gpio1087/value
echo 1 > /sys/class/gpio/gpio1088/value
echo 1 > /sys/class/gpio/gpio1089/value

cat /sys/kernel/debug/gpio

echo 0 > /sys/class/gpio/gpio1084/value
echo 0 > /sys/class/gpio/gpio1085/value
echo 0 > /sys/class/gpio/gpio1086/value
echo 0 > /sys/class/gpio/gpio1087/value
echo 0 > /sys/class/gpio/gpio1088/value
echo 0 > /sys/class/gpio/gpio1089/value

示波器接上量 VDDIO VBAT 電壓， 啟動時WIFI_REG_ON是否有拉高， 32K是否有給，37.4M是否有起振， SDIO_CLK SDIO_CMD 的波形。

IOMUX檢查：
檢查sdio對應的pin的IOMUX關係是否正確，
busybox find /d/pinctrl -name pinmux-pins
cat xxx/xxx/pinmux-pins

pin 84 (gpio2-20): fe310000.dwmmc (GPIO UNCLAIMED) function sdio0 group sdio0-bus4
pin 85 (gpio2-21): fe310000.dwmmc (GPIO UNCLAIMED) function sdio0 group sdio0-bus4
pin 86 (gpio2-22): fe310000.dwmmc (GPIO UNCLAIMED) function sdio0 group sdio0-bus4
pin 87 (gpio2-23): fe310000.dwmmc (GPIO UNCLAIMED) function sdio0 group sdio0-bus4
pin 88 (gpio2-24): fe310000.dwmmc (GPIO UNCLAIMED) function sdio0 group sdio0-cmd
pin 89 (gpio2-25): fe310000.dwmmc (GPIO UNCLAIMED) function sdio0 group sdio0-clk

參考：

Rockchip-Developer-Guide-linux4.4-SDMMC-SDIO-eMMC.pdf