imx8qm平台用的是有WIFI和BT功能的Murata 芯片，型号是LBEE6U41LQ，WIFI采用sdio接口，由WL_EN控制上电；BT是UART1接口，由BT_EN控制上电；
/* bt enable*/SC_P_USDHC2_VSELECT
/* uart1 */SC_P_UART1_RXSC_P_UART1_TXSC_P_UART1_CTS_BSC_P_UART1_RTS_B/* wifi */SC_P_SPI2_SDO // IRQ gpio3 8SC_P_USDHC2_RESET_B //ENABLE gpio4 9/* USDHC2 SDIO*/SC_P_USDHC2_CLKSC_P_USDHC2_CMDSC_P_USDHC2_DATA0SC_P_USDHC2_DATA1SC_P_USDHC2_DATA2SC_P_USDHC2_DATA31.SDIO扫描不到设备，wifi起不来，加打印如下，四个频率都扫描不到。
2.wifi enable脚正常情况如下，基本上不会出现掉电：
3.不正常情况在scan sdio时wifi enable脚被拉低7s左右。
1.drivers/mmc/core/core.c -->mmc_rescan，在4个频率下扫描设备（400kHZ,300kHZ,200kHZ,100kHZ）
void mmc_rescan(struct work_struct *work)
{struct mmc_host *host = container_of(work, struct mmc_host, detect.work);int i;if (host->rescan_disable)return;for (i = 0; i < ARRAY_SIZE(freqs); i++) {if (!mmc_rescan_try_freq(host, max(freqs[i], host->f_min))){printk("%s freq[%d] OK!\n",__func__,freqs[i]);break;}if (freqs[i] <= host->f_min)break;}2.drivers/mmc/core/core.c --> mmc_rescan_try_freq ,在扫描前先发个sdio_reset(CMD52)命令，只有sdio设备会有响应，之后按照sdio(CMD5),sd,mmc的顺序扫描，一旦扫到立即返回
static int mmc_rescan_try_freq(struct mmc_host *host, unsigned freq)
{host->f_init = freq;/** sdio_reset sends CMD52 to reset card. Since we do not know* if the card is being re-initialized, just send it. CMD52* should be ignored by SD/eMMC cards.* Skip it if we already know that we do not support SDIO commands*/if (!(host->caps2 & MMC_CAP2_NO_SDIO))sdio_reset(host);mmc_go_idle(host);if (!(host->caps2 & MMC_CAP2_NO_SD))mmc_send_if_cond(host, host->ocr_avail);/* Order's important: probe SDIO, then SD, then MMC */if (!(host->caps2 & MMC_CAP2_NO_SDIO))if (!mmc_attach_sdio(host)){printk("%s line=%d\n",__FUNCTION__,__LINE__);return 0;}if (!(host->caps2 & MMC_CAP2_NO_SD))if (!mmc_attach_sd(host))return 0;if (!(host->caps2 & MMC_CAP2_NO_MMC))if (!mmc_attach_mmc(host))return 0;mmc_power_off(host);return -EIO;
}3.如果成功检测到设备，便会进行后续的mmc_sdio_init_card和mmc_add_card及sdio_add_func，进行建立设备节点等操作。
查看开机kernel log [ 8.382000] mmc0: new SDIO card at address 0001
/** Starting point for SDIO card init.*/
int mmc_attach_sdio(struct mmc_host *host)
{int err, i, funcs;u32 ocr, rocr;struct mmc_card *card;printk("%s line=%d\n",__FUNCTION__,__LINE__);WARN_ON(!host->claimed);
.....err = mmc_sdio_init_card(host, rocr, NULL, 0);......for (i = 0; i < funcs; i++, card->sdio_funcs++) {
#ifdef CONFIG_MMC_EMBEDDED_SDIOif (host->embedded_sdio_data.funcs) {struct sdio_func *tmp;tmp = sdio_alloc_func(host->card);} else {
#endif printk("%s line=%d\n",__FUNCTION__,__LINE__);err = sdio_init_func(host->card, i + 1);if (err)goto remove;}mmc_release_host(host);err = mmc_add_card(host->card);if (err)goto remove_added;/** ...then the SDIO functions.*/for (i = 0;i < funcs;i++) {err = sdio_add_func(host->card->sdio_func[i]);if (err)goto remove_added;}}---->sdio_read_func_cis(func);
1.首先wifi enable脚入手，原本一直以为是DPU资源调换过来后引起uhsdc3 clock有问题了，后面通过各种对比试验定位到问题在fsl-imx8qm-mek-domu.dts里面。
pinctrl_wifi: wifi {fsl,pins = <SC_P_USDHC2_RESET_B_LSIO_GPIO4_IO09 0x18000000SC_P_SPI2_SDO_LSIO_GPIO3_IO08 0x1E000000>;}; pinctrl_pciea: pcieagrp{fsl,pins = <SC_P_PCIE_CTRL0_CLKREQ_B_LSIO_GPIO4_IO27 0x06000021SC_P_PCIE_CTRL0_WAKE_B_LSIO_GPIO4_IO28 0x04000021SC_P_PCIE_CTRL0_PERST_B_LSIO_GPIO4_IO29 0x06000021SC_P_LVDS1_I2C0_SDA_LSIO_GPIO1_IO13 0x06000000SC_P_USDHC2_RESET_B_LSIO_GPIO4_IO09 0x06000021>;};
&pciea {ext_osc = <1>;pinctrl-names = "default";pinctrl-0 = <&pinctrl_pciea>;disable-gpio = <&gpio1 13 GPIO_ACTIVE_LOW>;reset-gpio = <&gpio4 29 GPIO_ACTIVE_LOW>;clkreq-gpio = <&gpio4 27 GPIO_ACTIVE_LOW>;epdev_on-supply = <&epdev_on>;status = "disabled";
};epdev_on: fixedregulator@100 {compatible = "regulator-fixed";regulator-min-microvolt = <3300000>;regulator-max-microvolt = <3300000>;regulator-name = "epdev_on";gpio = <&gpio4 9 0>;enable-active-high;};[ 1.155040] sdhci: Secure Digital Host Controller Interface driver
[ 1.155054] sdhci: Copyright(c) Pierre Ossman
[ 1.155143] sdhci-pltfm: SDHCI platform and OF driver helper
[ 1.203808] mmc2: CQHCI version 5.10
[ 1.203854] enable-sdio-wakeup ok
[ 1.203881] sdhci-esdhc-imx 5b030000.usdhc: assigned as wifi host
[ 1.204884] mmc_rescan line=2748
[ 1.211333] mmc_attach_sdio line=1136
[ 1.250588] mmc2: SDHCI controller on 5b030000.usdhc [5b030000.usdhc] using ADMA
[ 1.255110] mmc_rescan line=2748
[ 1.255132] mmc2: mmc_rescan_try_freq: trying to init card at 400000 Hz
[ 1.264293] Galcore version 6.2.4.190076
[ 1.269699] mmc_attach_sdio line=1136
[ 1.272419] sdio_read_cis line=239
[ 1.280186] mmc2: queuing unknown CIS tuple 0x80 (2 bytes)
[ 1.282545] random: fast init done
[ 1.285154] mmc2: queuing unknown CIS tuple 0x80 (7 bytes)
[ 1.289261] mmc2: queuing unknown CIS tuple 0x80 (6 bytes)
[ 1.300245] mmc2: queuing unknown CIS tuple 0x80 (31 bytes)
[ 1.303460] mmc2: queuing unknown CIS tuple 0x80 (7 bytes)
[ 1.312601] mmc2: queuing unknown CIS tuple 0x80 (25 bytes)
[ 1.319569] mmc_rescan freq[400000] OK!
[ 1.321768] mmc2: queuing unknown CIS tuple 0x80 (25 bytes)
[ 1.369956] sdio_init_func line=86
[ 1.369979] sdio_read_func_cis line=377
[ 1.369989] sdio_read_cis line=239
[ 1.371074] sdio_init_func line=86
[ 1.371086] sdio_read_func_cis line=377
[ 1.371095] sdio_read_cis line=239
[ 1.372121] sdio_init_func line=86
[ 1.372132] sdio_read_func_cis line=377
[ 1.372141] sdio_read_cis line=239
[ 1.373259] mmc2: new high speed SDIO card at address 0001
[ 1.373610] mmc_rescan_try_freq line=2643
[ 1.373622] mmc_rescan freq[400000] OK!
